/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3.reflect;

import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.lang3.Validate;
import org.apache.commons.lang3.builder.Builder;

 Utility methods focusing on type inspection, particularly with regard to
generics. 
Since:
3.0/**
 * <p> Utility methods focusing on type inspection, particularly with regard to
 * generics. </p>
 *
 * @since 3.0
 */
public class TypeUtils {

    
WildcardType builder. 
Since:
3.2/**
     * {@link WildcardType} builder.
     * @since 3.2
     */
    public static class WildcardTypeBuilder implements Builder<WildcardType> {
        
Constructor
/**
         * Constructor
         */
        private WildcardTypeBuilder() {
        }

        private Type[] upperBounds;
        private Type[] lowerBounds;

        
Specify upper bounds of the wildcard type to build.
Params:
bounds – to set
Returns:
this/**
         * Specify upper bounds of the wildcard type to build.
         * @param bounds to set
         * @return {@code this}
         */
        public WildcardTypeBuilder withUpperBounds(final Type... bounds) {
            this.upperBounds = bounds;
            return this;
        }

        
Specify lower bounds of the wildcard type to build.
Params:
bounds – to set
Returns:
this/**
         * Specify lower bounds of the wildcard type to build.
         * @param bounds to set
         * @return {@code this}
         */
        public WildcardTypeBuilder withLowerBounds(final Type... bounds) {
            this.lowerBounds = bounds;
            return this;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public WildcardType build() {
            return new WildcardTypeImpl(upperBounds, lowerBounds);
        }
    }

    
GenericArrayType implementation class.
Since:
3.2/**
     * GenericArrayType implementation class.
     * @since 3.2
     */
    private static final class GenericArrayTypeImpl implements GenericArrayType {
        private final Type componentType;

        
Constructor
Params:
componentType – of this array type/**
         * Constructor
         * @param componentType of this array type
         */
        private GenericArrayTypeImpl(final Type componentType) {
            this.componentType = componentType;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public Type getGenericComponentType() {
            return componentType;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public String toString() {
            return TypeUtils.toString(this);
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public boolean equals(final Object obj) {
            return obj == this || obj instanceof GenericArrayType && TypeUtils.equals(this, (GenericArrayType) obj);
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public int hashCode() {
            int result = 67 << 4;
            result |= componentType.hashCode();
            return result;
        }
    }

    
ParameterizedType implementation class.
Since:
3.2/**
     * ParameterizedType implementation class.
     * @since 3.2
     */
    private static final class ParameterizedTypeImpl implements ParameterizedType {
        private final Class<?> raw;
        private final Type useOwner;
        private final Type[] typeArguments;

        
Constructor
Params:
raw – type
useOwner – owner type to use, if any
typeArguments – formal type arguments/**
         * Constructor
         * @param raw type
         * @param useOwner owner type to use, if any
         * @param typeArguments formal type arguments
         */
        private ParameterizedTypeImpl(final Class<?> raw, final Type useOwner, final Type[] typeArguments) {
            this.raw = raw;
            this.useOwner = useOwner;
            this.typeArguments = typeArguments.clone();
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public Type getRawType() {
            return raw;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public Type getOwnerType() {
            return useOwner;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public Type[] getActualTypeArguments() {
            return typeArguments.clone();
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public String toString() {
            return TypeUtils.toString(this);
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public boolean equals(final Object obj) {
            return obj == this || obj instanceof ParameterizedType && TypeUtils.equals(this, ((ParameterizedType) obj));
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public int hashCode() {
            int result = 71 << 4;
            result |= raw.hashCode();
            result <<= 4;
            result |= Objects.hashCode(useOwner);
            result <<= 8;
            result |= Arrays.hashCode(typeArguments);
            return result;
        }
    }

    
WildcardType implementation class.
Since:
3.2/**
     * WildcardType implementation class.
     * @since 3.2
     */
    private static final class WildcardTypeImpl implements WildcardType {
        private static final Type[] EMPTY_BOUNDS = new Type[0];

        private final Type[] upperBounds;
        private final Type[] lowerBounds;

        
Constructor
Params:
upperBounds – of this type
lowerBounds – of this type/**
         * Constructor
         * @param upperBounds of this type
         * @param lowerBounds of this type
         */
        private WildcardTypeImpl(final Type[] upperBounds, final Type[] lowerBounds) {
            this.upperBounds = ObjectUtils.defaultIfNull(upperBounds, EMPTY_BOUNDS);
            this.lowerBounds = ObjectUtils.defaultIfNull(lowerBounds, EMPTY_BOUNDS);
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public Type[] getUpperBounds() {
            return upperBounds.clone();
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public Type[] getLowerBounds() {
            return lowerBounds.clone();
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public String toString() {
            return TypeUtils.toString(this);
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public boolean equals(final Object obj) {
            return obj == this || obj instanceof WildcardType && TypeUtils.equals(this, (WildcardType) obj);
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public int hashCode() {
            int result = 73 << 8;
            result |= Arrays.hashCode(upperBounds);
            result <<= 8;
            result |= Arrays.hashCode(lowerBounds);
            return result;
        }
    }

    
A wildcard instance matching ?. 
Since:
3.2/**
     * A wildcard instance matching {@code ?}.
     * @since 3.2
     */
    public static final WildcardType WILDCARD_ALL = wildcardType().withUpperBounds(Object.class).build();

    
TypeUtils instances should NOT be constructed in standard programming. Instead, the class should be used as TypeUtils.isAssignable(cls, toClass).
 
This
constructor is public to permit tools that require a JavaBean instance to
operate.
/**
     * <p>{@code TypeUtils} instances should NOT be constructed in standard
     * programming. Instead, the class should be used as
     * {@code TypeUtils.isAssignable(cls, toClass)}.</p> <p>This
     * constructor is public to permit tools that require a JavaBean instance to
     * operate.</p>
     */
    public TypeUtils() {
        super();
    }

    
Checks if the subject type may be implicitly cast to the target type following the Java generics rules. If both types are Class objects, the method returns the result of ClassUtils.isAssignable(Class<?>, Class<?>).
Params:
type – the subject type to be assigned to the target type
toType – the target type
Returns:
true if type is assignable to toType./**
     * <p>Checks if the subject type may be implicitly cast to the target type
     * following the Java generics rules. If both types are {@link Class}
     * objects, the method returns the result of
     * {@link ClassUtils#isAssignable(Class, Class)}.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toType the target type
     * @return {@code true} if {@code type} is assignable to {@code toType}.
     */
    public static boolean isAssignable(final Type type, final Type toType) {
        return isAssignable(type, toType, null);
    }

    
Checks if the subject type may be implicitly cast to the target type
following the Java generics rules.
Params:
type – the subject type to be assigned to the target type
toType – the target type
typeVarAssigns – optional map of type variable assignments
Returns:
true if type is assignable to toType./**
     * <p>Checks if the subject type may be implicitly cast to the target type
     * following the Java generics rules.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toType the target type
     * @param typeVarAssigns optional map of type variable assignments
     * @return {@code true} if {@code type} is assignable to {@code toType}.
     */
    private static boolean isAssignable(final Type type, final Type toType,
            final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (toType == null || toType instanceof Class<?>) {
            return isAssignable(type, (Class<?>) toType);
        }

        if (toType instanceof ParameterizedType) {
            return isAssignable(type, (ParameterizedType) toType, typeVarAssigns);
        }

        if (toType instanceof GenericArrayType) {
            return isAssignable(type, (GenericArrayType) toType, typeVarAssigns);
        }

        if (toType instanceof WildcardType) {
            return isAssignable(type, (WildcardType) toType, typeVarAssigns);
        }

        if (toType instanceof TypeVariable<?>) {
            return isAssignable(type, (TypeVariable<?>) toType, typeVarAssigns);
        }

        throw new IllegalStateException("found an unhandled type: " + toType);
    }

    
Checks if the subject type may be implicitly cast to the target class
following the Java generics rules.
Params:
type – the subject type to be assigned to the target type
toClass – the target class
Returns:
true if type is assignable to toClass./**
     * <p>Checks if the subject type may be implicitly cast to the target class
     * following the Java generics rules.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toClass the target class
     * @return {@code true} if {@code type} is assignable to {@code toClass}.
     */
    private static boolean isAssignable(final Type type, final Class<?> toClass) {
        if (type == null) {
            // consistency with ClassUtils.isAssignable() behavior
            return toClass == null || !toClass.isPrimitive();
        }

        // only a null type can be assigned to null type which
        // would have cause the previous to return true
        if (toClass == null) {
            return false;
        }

        // all types are assignable to themselves
        if (toClass.equals(type)) {
            return true;
        }

        if (type instanceof Class<?>) {
            // just comparing two classes
            return ClassUtils.isAssignable((Class<?>) type, toClass);
        }

        if (type instanceof ParameterizedType) {
            // only have to compare the raw type to the class
            return isAssignable(getRawType((ParameterizedType) type), toClass);
        }

        // *
        if (type instanceof TypeVariable<?>) {
            // if any of the bounds are assignable to the class, then the
            // type is assignable to the class.
            for (final Type bound : ((TypeVariable<?>) type).getBounds()) {
                if (isAssignable(bound, toClass)) {
                    return true;
                }
            }

            return false;
        }

        // the only classes to which a generic array type can be assigned
        // are class Object and array classes
        if (type instanceof GenericArrayType) {
            return toClass.equals(Object.class)
                    || toClass.isArray()
                    && isAssignable(((GenericArrayType) type).getGenericComponentType(), toClass
                            .getComponentType());
        }

        // wildcard types are not assignable to a class (though one would think
        // "? super Object" would be assignable to Object)
        if (type instanceof WildcardType) {
            return false;
        }

        throw new IllegalStateException("found an unhandled type: " + type);
    }

    
Checks if the subject type may be implicitly cast to the target
parameterized type following the Java generics rules.
Params:
type – the subject type to be assigned to the target type
toParameterizedType – the target parameterized type
typeVarAssigns – a map with type variables
Returns:
true if type is assignable to toType./**
     * <p>Checks if the subject type may be implicitly cast to the target
     * parameterized type following the Java generics rules.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toParameterizedType the target parameterized type
     * @param typeVarAssigns a map with type variables
     * @return {@code true} if {@code type} is assignable to {@code toType}.
     */
    private static boolean isAssignable(final Type type, final ParameterizedType toParameterizedType,
            final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (type == null) {
            return true;
        }

        // only a null type can be assigned to null type which
        // would have cause the previous to return true
        if (toParameterizedType == null) {
            return false;
        }

        // all types are assignable to themselves
        if (toParameterizedType.equals(type)) {
            return true;
        }

        // get the target type's raw type
        final Class<?> toClass = getRawType(toParameterizedType);
        // get the subject type's type arguments including owner type arguments
        // and supertype arguments up to and including the target class.
        final Map<TypeVariable<?>, Type> fromTypeVarAssigns = getTypeArguments(type, toClass, null);

        // null means the two types are not compatible
        if (fromTypeVarAssigns == null) {
            return false;
        }

        // compatible types, but there's no type arguments. this is equivalent
        // to comparing Map< ?, ? > to Map, and raw types are always assignable
        // to parameterized types.
        if (fromTypeVarAssigns.isEmpty()) {
            return true;
        }

        // get the target type's type arguments including owner type arguments
        final Map<TypeVariable<?>, Type> toTypeVarAssigns = getTypeArguments(toParameterizedType,
                toClass, typeVarAssigns);

        // now to check each type argument
        for (final TypeVariable<?> var : toTypeVarAssigns.keySet()) {
            final Type toTypeArg = unrollVariableAssignments(var, toTypeVarAssigns);
            final Type fromTypeArg = unrollVariableAssignments(var, fromTypeVarAssigns);

            if (toTypeArg == null && fromTypeArg instanceof Class) {
                continue;
            }

            // parameters must either be absent from the subject type, within
            // the bounds of the wildcard type, or be an exact match to the
            // parameters of the target type.
            if (fromTypeArg != null
                    && !toTypeArg.equals(fromTypeArg)
                    && !(toTypeArg instanceof WildcardType && isAssignable(fromTypeArg, toTypeArg,
                            typeVarAssigns))) {
                return false;
            }
        }
        return true;
    }

    
Look up var in typeVarAssigns transitively,
i.e. keep looking until the value found is not a type variable.
Params:
var – the type variable to look up
typeVarAssigns – the map used for the look up
Returns:
Type or null if some variable was not in the map
Since:
3.2/**
     * Look up {@code var} in {@code typeVarAssigns} <em>transitively</em>,
     * i.e. keep looking until the value found is <em>not</em> a type variable.
     * @param var the type variable to look up
     * @param typeVarAssigns the map used for the look up
     * @return Type or {@code null} if some variable was not in the map
     * @since 3.2
     */
    private static Type unrollVariableAssignments(TypeVariable<?> var, final Map<TypeVariable<?>, Type> typeVarAssigns) {
        Type result;
        do {
            result = typeVarAssigns.get(var);
            if (result instanceof TypeVariable<?> && !result.equals(var)) {
                var = (TypeVariable<?>) result;
                continue;
            }
            break;
        } while (true);
        return result;
    }

    
Checks if the subject type may be implicitly cast to the target
generic array type following the Java generics rules.
Params:
type – the subject type to be assigned to the target type
toGenericArrayType – the target generic array type
typeVarAssigns – a map with type variables
Returns:
true if type is assignable to toGenericArrayType./**
     * <p>Checks if the subject type may be implicitly cast to the target
     * generic array type following the Java generics rules.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toGenericArrayType the target generic array type
     * @param typeVarAssigns a map with type variables
     * @return {@code true} if {@code type} is assignable to
     * {@code toGenericArrayType}.
     */
    private static boolean isAssignable(final Type type, final GenericArrayType toGenericArrayType,
            final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (type == null) {
            return true;
        }

        // only a null type can be assigned to null type which
        // would have cause the previous to return true
        if (toGenericArrayType == null) {
            return false;
        }

        // all types are assignable to themselves
        if (toGenericArrayType.equals(type)) {
            return true;
        }

        final Type toComponentType = toGenericArrayType.getGenericComponentType();

        if (type instanceof Class<?>) {
            final Class<?> cls = (Class<?>) type;

            // compare the component types
            return cls.isArray()
                    && isAssignable(cls.getComponentType(), toComponentType, typeVarAssigns);
        }

        if (type instanceof GenericArrayType) {
            // compare the component types
            return isAssignable(((GenericArrayType) type).getGenericComponentType(),
                    toComponentType, typeVarAssigns);
        }

        if (type instanceof WildcardType) {
            // so long as one of the upper bounds is assignable, it's good
            for (final Type bound : getImplicitUpperBounds((WildcardType) type)) {
                if (isAssignable(bound, toGenericArrayType)) {
                    return true;
                }
            }

            return false;
        }

        if (type instanceof TypeVariable<?>) {
            // probably should remove the following logic and just return false.
            // type variables cannot specify arrays as bounds.
            for (final Type bound : getImplicitBounds((TypeVariable<?>) type)) {
                if (isAssignable(bound, toGenericArrayType)) {
                    return true;
                }
            }

            return false;
        }

        if (type instanceof ParameterizedType) {
            // the raw type of a parameterized type is never an array or
            // generic array, otherwise the declaration would look like this:
            // Collection[]< ? extends String > collection;
            return false;
        }

        throw new IllegalStateException("found an unhandled type: " + type);
    }

    
Checks if the subject type may be implicitly cast to the target
wildcard type following the Java generics rules.
Params:
type – the subject type to be assigned to the target type
toWildcardType – the target wildcard type
typeVarAssigns – a map with type variables
Returns:
true if type is assignable to toWildcardType./**
     * <p>Checks if the subject type may be implicitly cast to the target
     * wildcard type following the Java generics rules.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toWildcardType the target wildcard type
     * @param typeVarAssigns a map with type variables
     * @return {@code true} if {@code type} is assignable to
     * {@code toWildcardType}.
     */
    private static boolean isAssignable(final Type type, final WildcardType toWildcardType,
            final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (type == null) {
            return true;
        }

        // only a null type can be assigned to null type which
        // would have cause the previous to return true
        if (toWildcardType == null) {
            return false;
        }

        // all types are assignable to themselves
        if (toWildcardType.equals(type)) {
            return true;
        }

        final Type[] toUpperBounds = getImplicitUpperBounds(toWildcardType);
        final Type[] toLowerBounds = getImplicitLowerBounds(toWildcardType);

        if (type instanceof WildcardType) {
            final WildcardType wildcardType = (WildcardType) type;
            final Type[] upperBounds = getImplicitUpperBounds(wildcardType);
            final Type[] lowerBounds = getImplicitLowerBounds(wildcardType);

            for (Type toBound : toUpperBounds) {
                // if there are assignments for unresolved type variables,
                // now's the time to substitute them.
                toBound = substituteTypeVariables(toBound, typeVarAssigns);

                // each upper bound of the subject type has to be assignable to
                // each
                // upper bound of the target type
                for (final Type bound : upperBounds) {
                    if (!isAssignable(bound, toBound, typeVarAssigns)) {
                        return false;
                    }
                }
            }

            for (Type toBound : toLowerBounds) {
                // if there are assignments for unresolved type variables,
                // now's the time to substitute them.
                toBound = substituteTypeVariables(toBound, typeVarAssigns);

                // each lower bound of the target type has to be assignable to
                // each
                // lower bound of the subject type
                for (final Type bound : lowerBounds) {
                    if (!isAssignable(toBound, bound, typeVarAssigns)) {
                        return false;
                    }
                }
            }
            return true;
        }

        for (final Type toBound : toUpperBounds) {
            // if there are assignments for unresolved type variables,
            // now's the time to substitute them.
            if (!isAssignable(type, substituteTypeVariables(toBound, typeVarAssigns),
                    typeVarAssigns)) {
                return false;
            }
        }

        for (final Type toBound : toLowerBounds) {
            // if there are assignments for unresolved type variables,
            // now's the time to substitute them.
            if (!isAssignable(substituteTypeVariables(toBound, typeVarAssigns), type,
                    typeVarAssigns)) {
                return false;
            }
        }
        return true;
    }

    
Checks if the subject type may be implicitly cast to the target type
variable following the Java generics rules.
Params:
type – the subject type to be assigned to the target type
toTypeVariable – the target type variable
typeVarAssigns – a map with type variables
Returns:
true if type is assignable to toTypeVariable./**
     * <p>Checks if the subject type may be implicitly cast to the target type
     * variable following the Java generics rules.</p>
     *
     * @param type the subject type to be assigned to the target type
     * @param toTypeVariable the target type variable
     * @param typeVarAssigns a map with type variables
     * @return {@code true} if {@code type} is assignable to
     * {@code toTypeVariable}.
     */
    private static boolean isAssignable(final Type type, final TypeVariable<?> toTypeVariable,
            final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (type == null) {
            return true;
        }

        // only a null type can be assigned to null type which
        // would have cause the previous to return true
        if (toTypeVariable == null) {
            return false;
        }

        // all types are assignable to themselves
        if (toTypeVariable.equals(type)) {
            return true;
        }

        if (type instanceof TypeVariable<?>) {
            // a type variable is assignable to another type variable, if
            // and only if the former is the latter, extends the latter, or
            // is otherwise a descendant of the latter.
            final Type[] bounds = getImplicitBounds((TypeVariable<?>) type);

            for (final Type bound : bounds) {
                if (isAssignable(bound, toTypeVariable, typeVarAssigns)) {
                    return true;
                }
            }
        }

        if (type instanceof Class<?> || type instanceof ParameterizedType
                || type instanceof GenericArrayType || type instanceof WildcardType) {
            return false;
        }

        throw new IllegalStateException("found an unhandled type: " + type);
    }

    
Find the mapping for type in typeVarAssigns.
Params:
type – the type to be replaced
typeVarAssigns – the map with type variables
Throws:
IllegalArgumentException – if the type cannot be substituted
Returns:
the replaced type/**
     * <p>Find the mapping for {@code type} in {@code typeVarAssigns}.</p>
     *
     * @param type the type to be replaced
     * @param typeVarAssigns the map with type variables
     * @return the replaced type
     * @throws IllegalArgumentException if the type cannot be substituted
     */
    private static Type substituteTypeVariables(final Type type, final Map<TypeVariable<?>, Type> typeVarAssigns) {
        if (type instanceof TypeVariable<?> && typeVarAssigns != null) {
            final Type replacementType = typeVarAssigns.get(type);

            if (replacementType == null) {
                throw new IllegalArgumentException("missing assignment type for type variable "
                        + type);
            }
            return replacementType;
        }
        return type;
    }

    
Retrieves all the type arguments for this parameterized type including owner hierarchy arguments such as Outer<K,V>.Inner<T>.DeepInner<E> . The arguments are returned in a Map specifying the argument type for each TypeVariable. 
Params:
type – specifies the subject parameterized type from which to
            harvest the parameters.
Returns:
a Map of the type arguments to their respective type variables./**
     * <p>Retrieves all the type arguments for this parameterized type
     * including owner hierarchy arguments such as
     * {@code Outer<K,V>.Inner<T>.DeepInner<E>} .
     * The arguments are returned in a
     * {@link Map} specifying the argument type for each {@link TypeVariable}.
     * </p>
     *
     * @param type specifies the subject parameterized type from which to
     *             harvest the parameters.
     * @return a {@code Map} of the type arguments to their respective type
     * variables.
     */
    public static Map<TypeVariable<?>, Type> getTypeArguments(final ParameterizedType type) {
        return getTypeArguments(type, getRawType(type), null);
    }

    
Gets the type arguments of a class/interface based on a subtype. For instance, this method will determine that both of the parameters for the interface Map are Object for the subtype Properties even though the subtype does not directly implement the Map interface.
This method returns null if type is not assignable to toClass. It returns an empty map if none of the classes or interfaces in its inheritance hierarchy specify any type arguments.
A side effect of this method is that it also retrieves the type arguments for the classes and interfaces that are part of the hierarchy between type and toClass. So with the above example, this method will also determine that the type arguments for Hashtable are also both Object. In cases where the interface specified by toClass is (indirectly) implemented more than once (e.g. where toClass specifies the interface Iterable and type specifies a parameterized type that implements both Set and Collection), this method will look at the inheritance hierarchy of only one of the implementations/subclasses; the first interface encountered that isn't a subinterface to one of the others in the type to toClass hierarchy.
Params:
type – the type from which to determine the type parameters of toClass
toClass – the class whose type parameters are to be determined based on the subtype type
Returns:
a Map of the type assignments for the type variables in each type in the inheritance hierarchy from type to toClass inclusive./**
     * <p>Gets the type arguments of a class/interface based on a subtype. For
     * instance, this method will determine that both of the parameters for the
     * interface {@link Map} are {@link Object} for the subtype
     * {@link java.util.Properties Properties} even though the subtype does not
     * directly implement the {@code Map} interface.</p>
     * <p>This method returns {@code null} if {@code type} is not assignable to
     * {@code toClass}. It returns an empty map if none of the classes or
     * interfaces in its inheritance hierarchy specify any type arguments.</p>
     * <p>A side effect of this method is that it also retrieves the type
     * arguments for the classes and interfaces that are part of the hierarchy
     * between {@code type} and {@code toClass}. So with the above
     * example, this method will also determine that the type arguments for
     * {@link java.util.Hashtable Hashtable} are also both {@code Object}.
     * In cases where the interface specified by {@code toClass} is
     * (indirectly) implemented more than once (e.g. where {@code toClass}
     * specifies the interface {@link java.lang.Iterable Iterable} and
     * {@code type} specifies a parameterized type that implements both
     * {@link java.util.Set Set} and {@link java.util.Collection Collection}),
     * this method will look at the inheritance hierarchy of only one of the
     * implementations/subclasses; the first interface encountered that isn't a
     * subinterface to one of the others in the {@code type} to
     * {@code toClass} hierarchy.</p>
     *
     * @param type the type from which to determine the type parameters of
     * {@code toClass}
     * @param toClass the class whose type parameters are to be determined based
     * on the subtype {@code type}
     * @return a {@code Map} of the type assignments for the type variables in
     * each type in the inheritance hierarchy from {@code type} to
     * {@code toClass} inclusive.
     */
    public static Map<TypeVariable<?>, Type> getTypeArguments(final Type type, final Class<?> toClass) {
        return getTypeArguments(type, toClass, null);
    }

    
Return a map of the type arguments of type in the context of toClass.
Params:
type – the type in question
toClass – the class
subtypeVarAssigns – a map with type variables
Returns:
the Map with type arguments/**
     * <p>Return a map of the type arguments of {@code type} in the context of {@code toClass}.</p>
     *
     * @param type the type in question
     * @param toClass the class
     * @param subtypeVarAssigns a map with type variables
     * @return the {@code Map} with type arguments
     */
    private static Map<TypeVariable<?>, Type> getTypeArguments(final Type type, final Class<?> toClass,
            final Map<TypeVariable<?>, Type> subtypeVarAssigns) {
        if (type instanceof Class<?>) {
            return getTypeArguments((Class<?>) type, toClass, subtypeVarAssigns);
        }

        if (type instanceof ParameterizedType) {
            return getTypeArguments((ParameterizedType) type, toClass, subtypeVarAssigns);
        }

        if (type instanceof GenericArrayType) {
            return getTypeArguments(((GenericArrayType) type).getGenericComponentType(), toClass
                    .isArray() ? toClass.getComponentType() : toClass, subtypeVarAssigns);
        }

        // since wildcard types are not assignable to classes, should this just
        // return null?
        if (type instanceof WildcardType) {
            for (final Type bound : getImplicitUpperBounds((WildcardType) type)) {
                // find the first bound that is assignable to the target class
                if (isAssignable(bound, toClass)) {
                    return getTypeArguments(bound, toClass, subtypeVarAssigns);
                }
            }

            return null;
        }

        if (type instanceof TypeVariable<?>) {
            for (final Type bound : getImplicitBounds((TypeVariable<?>) type)) {
                // find the first bound that is assignable to the target class
                if (isAssignable(bound, toClass)) {
                    return getTypeArguments(bound, toClass, subtypeVarAssigns);
                }
            }

            return null;
        }
        throw new IllegalStateException("found an unhandled type: " + type);
    }

    
Return a map of the type arguments of a parameterized type in the context of toClass.
Params:
parameterizedType – the parameterized type
toClass – the class
subtypeVarAssigns – a map with type variables
Returns:
the Map with type arguments/**
     * <p>Return a map of the type arguments of a parameterized type in the context of {@code toClass}.</p>
     *
     * @param parameterizedType the parameterized type
     * @param toClass the class
     * @param subtypeVarAssigns a map with type variables
     * @return the {@code Map} with type arguments
     */
    private static Map<TypeVariable<?>, Type> getTypeArguments(
            final ParameterizedType parameterizedType, final Class<?> toClass,
            final Map<TypeVariable<?>, Type> subtypeVarAssigns) {
        final Class<?> cls = getRawType(parameterizedType);

        // make sure they're assignable
        if (!isAssignable(cls, toClass)) {
            return null;
        }

        final Type ownerType = parameterizedType.getOwnerType();
        Map<TypeVariable<?>, Type> typeVarAssigns;

        if (ownerType instanceof ParameterizedType) {
            // get the owner type arguments first
            final ParameterizedType parameterizedOwnerType = (ParameterizedType) ownerType;
            typeVarAssigns = getTypeArguments(parameterizedOwnerType,
                    getRawType(parameterizedOwnerType), subtypeVarAssigns);
        } else {
            // no owner, prep the type variable assignments map
            typeVarAssigns = subtypeVarAssigns == null ? new HashMap<TypeVariable<?>, Type>()
                    : new HashMap<>(subtypeVarAssigns);
        }

        // get the subject parameterized type's arguments
        final Type[] typeArgs = parameterizedType.getActualTypeArguments();
        // and get the corresponding type variables from the raw class
        final TypeVariable<?>[] typeParams = cls.getTypeParameters();

        // map the arguments to their respective type variables
        for (int i = 0; i < typeParams.length; i++) {
            final Type typeArg = typeArgs[i];
            typeVarAssigns.put(typeParams[i], typeVarAssigns.containsKey(typeArg) ? typeVarAssigns
                    .get(typeArg) : typeArg);
        }

        if (toClass.equals(cls)) {
            // target class has been reached. Done.
            return typeVarAssigns;
        }

        // walk the inheritance hierarchy until the target class is reached
        return getTypeArguments(getClosestParentType(cls, toClass), toClass, typeVarAssigns);
    }

    
Return a map of the type arguments of a class in the context of toClass.
Params:
cls – the class in question
toClass – the context class
subtypeVarAssigns – a map with type variables
Returns:
the Map with type arguments/**
     * <p>Return a map of the type arguments of a class in the context of {@code toClass}.</p>
     *
     * @param cls the class in question
     * @param toClass the context class
     * @param subtypeVarAssigns a map with type variables
     * @return the {@code Map} with type arguments
     */
    private static Map<TypeVariable<?>, Type> getTypeArguments(Class<?> cls, final Class<?> toClass,
            final Map<TypeVariable<?>, Type> subtypeVarAssigns) {
        // make sure they're assignable
        if (!isAssignable(cls, toClass)) {
            return null;
        }

        // can't work with primitives
        if (cls.isPrimitive()) {
            // both classes are primitives?
            if (toClass.isPrimitive()) {
                // dealing with widening here. No type arguments to be
                // harvested with these two types.
                return new HashMap<>();
            }

            // work with wrapper the wrapper class instead of the primitive
            cls = ClassUtils.primitiveToWrapper(cls);
        }

        // create a copy of the incoming map, or an empty one if it's null
        final HashMap<TypeVariable<?>, Type> typeVarAssigns = subtypeVarAssigns == null ? new HashMap<TypeVariable<?>, Type>()
                : new HashMap<>(subtypeVarAssigns);

        // has target class been reached?
        if (toClass.equals(cls)) {
            return typeVarAssigns;
        }

        // walk the inheritance hierarchy until the target class is reached
        return getTypeArguments(getClosestParentType(cls, toClass), toClass, typeVarAssigns);
    }

    
Tries to determine the type arguments of a class/interface based on a super parameterized type's type arguments. This method is the inverse of getTypeArguments(Type, Class<?>) which gets a class/interface's type arguments based on a subtype. It is far more limited in determining the type arguments for the subject class's type variables in that it can only determine those parameters that map from the subject Class object to the supertype.
 
Example: 
TreeSet sets its parameter as the parameter for NavigableSet, which in turn sets the parameter of SortedSet, which in turn sets the parameter of Set, which in turn sets the parameter of Collection, which in turn sets the parameter of Iterable. Since TreeSet's parameter maps (indirectly) to Iterable's parameter, it will be able to determine that based on the super type Iterable<? extends
Map<Integer, ? extends Collection<?>>>, the parameter of TreeSet is ? extends Map<Integer, ? extends
Collection<?>>.
Params:
cls – the class whose type parameters are to be determined, not null
superType – the super type from which cls's type arguments are to be determined, not null
Returns:
a Map of the type assignments that could be determined for the type variables in each type in the inheritance hierarchy from type to toClass inclusive./**
     * <p>Tries to determine the type arguments of a class/interface based on a
     * super parameterized type's type arguments. This method is the inverse of
     * {@link #getTypeArguments(Type, Class)} which gets a class/interface's
     * type arguments based on a subtype. It is far more limited in determining
     * the type arguments for the subject class's type variables in that it can
     * only determine those parameters that map from the subject {@link Class}
     * object to the supertype.</p> <p>Example: {@link java.util.TreeSet
     * TreeSet} sets its parameter as the parameter for
     * {@link java.util.NavigableSet NavigableSet}, which in turn sets the
     * parameter of {@link java.util.SortedSet}, which in turn sets the
     * parameter of {@link Set}, which in turn sets the parameter of
     * {@link java.util.Collection}, which in turn sets the parameter of
     * {@link java.lang.Iterable}. Since {@code TreeSet}'s parameter maps
     * (indirectly) to {@code Iterable}'s parameter, it will be able to
     * determine that based on the super type {@code Iterable<? extends
     * Map<Integer, ? extends Collection<?>>>}, the parameter of
     * {@code TreeSet} is {@code ? extends Map<Integer, ? extends
     * Collection<?>>}.</p>
     *
     * @param cls the class whose type parameters are to be determined, not {@code null}
     * @param superType the super type from which {@code cls}'s type
     * arguments are to be determined, not {@code null}
     * @return a {@code Map} of the type assignments that could be determined
     * for the type variables in each type in the inheritance hierarchy from
     * {@code type} to {@code toClass} inclusive.
     */
    public static Map<TypeVariable<?>, Type> determineTypeArguments(final Class<?> cls,
            final ParameterizedType superType) {
        Validate.notNull(cls, "cls is null");
        Validate.notNull(superType, "superType is null");

        final Class<?> superClass = getRawType(superType);

        // compatibility check
        if (!isAssignable(cls, superClass)) {
            return null;
        }

        if (cls.equals(superClass)) {
            return getTypeArguments(superType, superClass, null);
        }

        // get the next class in the inheritance hierarchy
        final Type midType = getClosestParentType(cls, superClass);

        // can only be a class or a parameterized type
        if (midType instanceof Class<?>) {
            return determineTypeArguments((Class<?>) midType, superType);
        }

        final ParameterizedType midParameterizedType = (ParameterizedType) midType;
        final Class<?> midClass = getRawType(midParameterizedType);
        // get the type variables of the mid class that map to the type
        // arguments of the super class
        final Map<TypeVariable<?>, Type> typeVarAssigns = determineTypeArguments(midClass, superType);
        // map the arguments of the mid type to the class type variables
        mapTypeVariablesToArguments(cls, midParameterizedType, typeVarAssigns);

        return typeVarAssigns;
    }

    
Performs a mapping of type variables.
Params:
cls – the class in question
parameterizedType – the parameterized type
typeVarAssigns – the map to be filled
Type parameters:
<T> – the generic type of the class in question/**
     * <p>Performs a mapping of type variables.</p>
     *
     * @param <T> the generic type of the class in question
     * @param cls the class in question
     * @param parameterizedType the parameterized type
     * @param typeVarAssigns the map to be filled
     */
    private static <T> void mapTypeVariablesToArguments(final Class<T> cls,
            final ParameterizedType parameterizedType, final Map<TypeVariable<?>, Type> typeVarAssigns) {
        // capture the type variables from the owner type that have assignments
        final Type ownerType = parameterizedType.getOwnerType();

        if (ownerType instanceof ParameterizedType) {
            // recursion to make sure the owner's owner type gets processed
            mapTypeVariablesToArguments(cls, (ParameterizedType) ownerType, typeVarAssigns);
        }

        // parameterizedType is a generic interface/class (or it's in the owner
        // hierarchy of said interface/class) implemented/extended by the class
        // cls. Find out which type variables of cls are type arguments of
        // parameterizedType:
        final Type[] typeArgs = parameterizedType.getActualTypeArguments();

        // of the cls's type variables that are arguments of parameterizedType,
        // find out which ones can be determined from the super type's arguments
        final TypeVariable<?>[] typeVars = getRawType(parameterizedType).getTypeParameters();

        // use List view of type parameters of cls so the contains() method can be used:
        final List<TypeVariable<Class<T>>> typeVarList = Arrays.asList(cls
                .getTypeParameters());

        for (int i = 0; i < typeArgs.length; i++) {
            final TypeVariable<?> typeVar = typeVars[i];
            final Type typeArg = typeArgs[i];

            // argument of parameterizedType is a type variable of cls
            if (typeVarList.contains(typeArg)
            // type variable of parameterizedType has an assignment in
                    // the super type.
                    && typeVarAssigns.containsKey(typeVar)) {
                // map the assignment to the cls's type variable
                typeVarAssigns.put((TypeVariable<?>) typeArg, typeVarAssigns.get(typeVar));
            }
        }
    }

    
Get the closest parent type to the super class specified by superClass.
Params:
cls – the class in question
superClass – the super class
Returns:
the closes parent type/**
     * <p>Get the closest parent type to the
     * super class specified by {@code superClass}.</p>
     *
     * @param cls the class in question
     * @param superClass the super class
     * @return the closes parent type
     */
    private static Type getClosestParentType(final Class<?> cls, final Class<?> superClass) {
        // only look at the interfaces if the super class is also an interface
        if (superClass.isInterface()) {
            // get the generic interfaces of the subject class
            final Type[] interfaceTypes = cls.getGenericInterfaces();
            // will hold the best generic interface match found
            Type genericInterface = null;

            // find the interface closest to the super class
            for (final Type midType : interfaceTypes) {
                Class<?> midClass = null;

                if (midType instanceof ParameterizedType) {
                    midClass = getRawType((ParameterizedType) midType);
                } else if (midType instanceof Class<?>) {
                    midClass = (Class<?>) midType;
                } else {
                    throw new IllegalStateException("Unexpected generic"
                            + " interface type found: " + midType);
                }

                // check if this interface is further up the inheritance chain
                // than the previously found match
                if (isAssignable(midClass, superClass)
                        && isAssignable(genericInterface, (Type) midClass)) {
                    genericInterface = midType;
                }
            }

            // found a match?
            if (genericInterface != null) {
                return genericInterface;
            }
        }

        // none of the interfaces were descendants of the target class, so the
        // super class has to be one, instead
        return cls.getGenericSuperclass();
    }

    
Checks if the given value can be assigned to the target type
following the Java generics rules.
Params:
value – the value to be checked
type – the target type
Returns:
true if value is an instance of type./**
     * <p>Checks if the given value can be assigned to the target type
     * following the Java generics rules.</p>
     *
     * @param value the value to be checked
     * @param type the target type
     * @return {@code true} if {@code value} is an instance of {@code type}.
     */
    public static boolean isInstance(final Object value, final Type type) {
        if (type == null) {
            return false;
        }

        return value == null ? !(type instanceof Class<?>) || !((Class<?>) type).isPrimitive()
                : isAssignable(value.getClass(), type, null);
    }

    
This method strips out the redundant upper bound types in type
variable types and wildcard types (or it would with wildcard types if
multiple upper bounds were allowed).
 
Example, with the variable
type declaration:
<K extends java.util.Collection<String> &
java.util.List<String>>
 since List is a subinterface of Collection, this method will return the bounds as if the declaration had been: 
<K extends java.util.List<String>>
Params:
bounds – an array of types representing the upper bounds of either WildcardType or TypeVariable, not null.
Returns:
an array containing the values from bounds minus the redundant types./**
     * <p>This method strips out the redundant upper bound types in type
     * variable types and wildcard types (or it would with wildcard types if
     * multiple upper bounds were allowed).</p> <p>Example, with the variable
     * type declaration:
     *
     * <pre>&lt;K extends java.util.Collection&lt;String&gt; &amp;
     * java.util.List&lt;String&gt;&gt;</pre>
     *
     * <p>
     * since {@code List} is a subinterface of {@code Collection},
     * this method will return the bounds as if the declaration had been:
     * </p>
     *
     * <pre>&lt;K extends java.util.List&lt;String&gt;&gt;</pre>
     *
     * @param bounds an array of types representing the upper bounds of either
     * {@link WildcardType} or {@link TypeVariable}, not {@code null}.
     * @return an array containing the values from {@code bounds} minus the
     * redundant types.
     */
    public static Type[] normalizeUpperBounds(final Type[] bounds) {
        Validate.notNull(bounds, "null value specified for bounds array");
        // don't bother if there's only one (or none) type
        if (bounds.length < 2) {
            return bounds;
        }

        final Set<Type> types = new HashSet<>(bounds.length);

        for (final Type type1 : bounds) {
            boolean subtypeFound = false;

            for (final Type type2 : bounds) {
                if (type1 != type2 && isAssignable(type2, type1, null)) {
                    subtypeFound = true;
                    break;
                }
            }

            if (!subtypeFound) {
                types.add(type1);
            }
        }

        return types.toArray(new Type[types.size()]);
    }

    
Returns an array containing the sole type of Object if TypeVariable.getBounds() returns an empty array. Otherwise, it returns the result of TypeVariable.getBounds() passed into normalizeUpperBounds.
Params:
typeVariable – the subject type variable, not null
Returns:
a non-empty array containing the bounds of the type variable./**
     * <p>Returns an array containing the sole type of {@link Object} if
     * {@link TypeVariable#getBounds()} returns an empty array. Otherwise, it
     * returns the result of {@link TypeVariable#getBounds()} passed into
     * {@link #normalizeUpperBounds}.</p>
     *
     * @param typeVariable the subject type variable, not {@code null}
     * @return a non-empty array containing the bounds of the type variable.
     */
    public static Type[] getImplicitBounds(final TypeVariable<?> typeVariable) {
        Validate.notNull(typeVariable, "typeVariable is null");
        final Type[] bounds = typeVariable.getBounds();

        return bounds.length == 0 ? new Type[] { Object.class } : normalizeUpperBounds(bounds);
    }

    
Returns an array containing the sole value of Object if WildcardType.getUpperBounds() returns an empty array. Otherwise, it returns the result of WildcardType.getUpperBounds() passed into normalizeUpperBounds.
Params:
wildcardType – the subject wildcard type, not null
Returns:
a non-empty array containing the upper bounds of the wildcard
type./**
     * <p>Returns an array containing the sole value of {@link Object} if
     * {@link WildcardType#getUpperBounds()} returns an empty array. Otherwise,
     * it returns the result of {@link WildcardType#getUpperBounds()}
     * passed into {@link #normalizeUpperBounds}.</p>
     *
     * @param wildcardType the subject wildcard type, not {@code null}
     * @return a non-empty array containing the upper bounds of the wildcard
     * type.
     */
    public static Type[] getImplicitUpperBounds(final WildcardType wildcardType) {
        Validate.notNull(wildcardType, "wildcardType is null");
        final Type[] bounds = wildcardType.getUpperBounds();

        return bounds.length == 0 ? new Type[] { Object.class } : normalizeUpperBounds(bounds);
    }

    
Returns an array containing a single value of null if WildcardType.getLowerBounds() returns an empty array. Otherwise, it returns the result of WildcardType.getLowerBounds().
Params:
wildcardType – the subject wildcard type, not null
Returns:
a non-empty array containing the lower bounds of the wildcard
type./**
     * <p>Returns an array containing a single value of {@code null} if
     * {@link WildcardType#getLowerBounds()} returns an empty array. Otherwise,
     * it returns the result of {@link WildcardType#getLowerBounds()}.</p>
     *
     * @param wildcardType the subject wildcard type, not {@code null}
     * @return a non-empty array containing the lower bounds of the wildcard
     * type.
     */
    public static Type[] getImplicitLowerBounds(final WildcardType wildcardType) {
        Validate.notNull(wildcardType, "wildcardType is null");
        final Type[] bounds = wildcardType.getLowerBounds();

        return bounds.length == 0 ? new Type[] { null } : bounds;
    }

    
Determines whether or not specified types satisfy the bounds of their mapped type variables. When a type parameter extends another (such as <T, S extends T>), uses another as a type parameter (such as <T, S extends Comparable>>), or otherwise depends on another type variable to be specified, the dependencies must be included in typeVarAssigns.
Params:
typeVarAssigns – specifies the potential types to be assigned to the type variables, not null.
Returns:
whether or not the types can be assigned to their respective type
variables./**
     * <p>Determines whether or not specified types satisfy the bounds of their
     * mapped type variables. When a type parameter extends another (such as
     * {@code <T, S extends T>}), uses another as a type parameter (such as
     * {@code <T, S extends Comparable>>}), or otherwise depends on
     * another type variable to be specified, the dependencies must be included
     * in {@code typeVarAssigns}.</p>
     *
     * @param typeVarAssigns specifies the potential types to be assigned to the
     * type variables, not {@code null}.
     * @return whether or not the types can be assigned to their respective type
     * variables.
     */
    public static boolean typesSatisfyVariables(final Map<TypeVariable<?>, Type> typeVarAssigns) {
        Validate.notNull(typeVarAssigns, "typeVarAssigns is null");
        // all types must be assignable to all the bounds of the their mapped
        // type variable.
        for (final Map.Entry<TypeVariable<?>, Type> entry : typeVarAssigns.entrySet()) {
            final TypeVariable<?> typeVar = entry.getKey();
            final Type type = entry.getValue();

            for (final Type bound : getImplicitBounds(typeVar)) {
                if (!isAssignable(type, substituteTypeVariables(bound, typeVarAssigns),
                        typeVarAssigns)) {
                    return false;
                }
            }
        }
        return true;
    }

    
Transforms the passed in type to a Class object. Type-checking method of convenience.
Params:
parameterizedType – the type to be converted
Throws:
IllegalStateException – if the conversion fails
Returns:
the corresponding Class object/**
     * <p>Transforms the passed in type to a {@link Class} object. Type-checking method of convenience.</p>
     *
     * @param parameterizedType the type to be converted
     * @return the corresponding {@code Class} object
     * @throws IllegalStateException if the conversion fails
     */
    private static Class<?> getRawType(final ParameterizedType parameterizedType) {
        final Type rawType = parameterizedType.getRawType();

        // check if raw type is a Class object
        // not currently necessary, but since the return type is Type instead of
        // Class, there's enough reason to believe that future versions of Java
        // may return other Type implementations. And type-safety checking is
        // rarely a bad idea.
        if (!(rawType instanceof Class<?>)) {
            throw new IllegalStateException("Wait... What!? Type of rawType: " + rawType);
        }

        return (Class<?>) rawType;
    }

    
Get the raw type of a Java type, given its context. Primarily for use with TypeVariables and GenericArrayTypes, or when you do not know the runtime type of type: if you know you have a Class instance, it is already raw; if you know you have a ParameterizedType, its raw type is only a method call away.
Params:
type – to resolve
assigningType – type to be resolved against
Returns:
the resolved Class object or null if the type could not be resolved/**
     * <p>Get the raw type of a Java type, given its context. Primarily for use
     * with {@link TypeVariable}s and {@link GenericArrayType}s, or when you do
     * not know the runtime type of {@code type}: if you know you have a
     * {@link Class} instance, it is already raw; if you know you have a
     * {@link ParameterizedType}, its raw type is only a method call away.</p>
     *
     * @param type to resolve
     * @param assigningType type to be resolved against
     * @return the resolved {@link Class} object or {@code null} if
     * the type could not be resolved
     */
    public static Class<?> getRawType(final Type type, final Type assigningType) {
        if (type instanceof Class<?>) {
            // it is raw, no problem
            return (Class<?>) type;
        }

        if (type instanceof ParameterizedType) {
            // simple enough to get the raw type of a ParameterizedType
            return getRawType((ParameterizedType) type);
        }

        if (type instanceof TypeVariable<?>) {
            if (assigningType == null) {
                return null;
            }

            // get the entity declaring this type variable
            final Object genericDeclaration = ((TypeVariable<?>) type).getGenericDeclaration();

            // can't get the raw type of a method- or constructor-declared type
            // variable
            if (!(genericDeclaration instanceof Class<?>)) {
                return null;
            }

            // get the type arguments for the declaring class/interface based
            // on the enclosing type
            final Map<TypeVariable<?>, Type> typeVarAssigns = getTypeArguments(assigningType,
                    (Class<?>) genericDeclaration);

            // enclosingType has to be a subclass (or subinterface) of the
            // declaring type
            if (typeVarAssigns == null) {
                return null;
            }

            // get the argument assigned to this type variable
            final Type typeArgument = typeVarAssigns.get(type);

            if (typeArgument == null) {
                return null;
            }

            // get the argument for this type variable
            return getRawType(typeArgument, assigningType);
        }

        if (type instanceof GenericArrayType) {
            // get raw component type
            final Class<?> rawComponentType = getRawType(((GenericArrayType) type)
                    .getGenericComponentType(), assigningType);

            // create array type from raw component type and return its class
            return Array.newInstance(rawComponentType, 0).getClass();
        }

        // (hand-waving) this is not the method you're looking for
        if (type instanceof WildcardType) {
            return null;
        }

        throw new IllegalArgumentException("unknown type: " + type);
    }

    
Learn whether the specified type denotes an array type.
Params:
type – the type to be checked
Returns:
true if type is an array class or a GenericArrayType./**
     * Learn whether the specified type denotes an array type.
     * @param type the type to be checked
     * @return {@code true} if {@code type} is an array class or a {@link GenericArrayType}.
     */
    public static boolean isArrayType(final Type type) {
        return type instanceof GenericArrayType || type instanceof Class<?> && ((Class<?>) type).isArray();
    }

    
Get the array component type of type. 
Params:
type – the type to be checked
Returns:
component type or null if type is not an array type/**
     * Get the array component type of {@code type}.
     * @param type the type to be checked
     * @return component type or null if type is not an array type
     */
    public static Type getArrayComponentType(final Type type) {
        if (type instanceof Class<?>) {
            final Class<?> clazz = (Class<?>) type;
            return clazz.isArray() ? clazz.getComponentType() : null;
        }
        if (type instanceof GenericArrayType) {
            return ((GenericArrayType) type).getGenericComponentType();
        }
        return null;
    }

    
Get a type representing type with variable assignments "unrolled." 
Params:
typeArguments – as from getTypeArguments(Type, Class<?>)
type – the type to unroll variable assignments for
Returns:
Type
Since:
3.2/**
     * Get a type representing {@code type} with variable assignments "unrolled."
     *
     * @param typeArguments as from {@link TypeUtils#getTypeArguments(Type, Class)}
     * @param type the type to unroll variable assignments for
     * @return Type
     * @since 3.2
     */
    public static Type unrollVariables(Map<TypeVariable<?>, Type> typeArguments, final Type type) {
        if (typeArguments == null) {
            typeArguments = Collections.emptyMap();
        }
        if (containsTypeVariables(type)) {
            if (type instanceof TypeVariable<?>) {
                return unrollVariables(typeArguments, typeArguments.get(type));
            }
            if (type instanceof ParameterizedType) {
                final ParameterizedType p = (ParameterizedType) type;
                final Map<TypeVariable<?>, Type> parameterizedTypeArguments;
                if (p.getOwnerType() == null) {
                    parameterizedTypeArguments = typeArguments;
                } else {
                    parameterizedTypeArguments = new HashMap<>(typeArguments);
                    parameterizedTypeArguments.putAll(TypeUtils.getTypeArguments(p));
                }
                final Type[] args = p.getActualTypeArguments();
                for (int i = 0; i < args.length; i++) {
                    final Type unrolled = unrollVariables(parameterizedTypeArguments, args[i]);
                    if (unrolled != null) {
                        args[i] = unrolled;
                    }
                }
                return parameterizeWithOwner(p.getOwnerType(), (Class<?>) p.getRawType(), args);
            }
            if (type instanceof WildcardType) {
                final WildcardType wild = (WildcardType) type;
                return wildcardType().withUpperBounds(unrollBounds(typeArguments, wild.getUpperBounds()))
                    .withLowerBounds(unrollBounds(typeArguments, wild.getLowerBounds())).build();
            }
        }
        return type;
    }

    
Local helper method to unroll variables in a type bounds array.
Params:
typeArguments – assignments Map
bounds – in which to expand variables
Returns:
bounds with any variables reassigned
Since:
3.2/**
     * Local helper method to unroll variables in a type bounds array.
     *
     * @param typeArguments assignments {@link Map}
     * @param bounds in which to expand variables
     * @return {@code bounds} with any variables reassigned
     * @since 3.2
     */
    private static Type[] unrollBounds(final Map<TypeVariable<?>, Type> typeArguments, final Type[] bounds) {
        Type[] result = bounds;
        int i = 0;
        for (; i < result.length; i++) {
            final Type unrolled = unrollVariables(typeArguments, result[i]);
            if (unrolled == null) {
                result = ArrayUtils.remove(result, i--);
            } else {
                result[i] = unrolled;
            }
        }
        return result;
    }

    
Learn, recursively, whether any of the type parameters associated with type are bound to variables. 
Params:
type – the type to check for type variables
Returns:
boolean
Since:
3.2/**
     * Learn, recursively, whether any of the type parameters associated with {@code type} are bound to variables.
     *
     * @param type the type to check for type variables
     * @return boolean
     * @since 3.2
     */
    public static boolean containsTypeVariables(final Type type) {
        if (type instanceof TypeVariable<?>) {
            return true;
        }
        if (type instanceof Class<?>) {
            return ((Class<?>) type).getTypeParameters().length > 0;
        }
        if (type instanceof ParameterizedType) {
            for (final Type arg : ((ParameterizedType) type).getActualTypeArguments()) {
                if (containsTypeVariables(arg)) {
                    return true;
                }
            }
            return false;
        }
        if (type instanceof WildcardType) {
            final WildcardType wild = (WildcardType) type;
            return containsTypeVariables(TypeUtils.getImplicitLowerBounds(wild)[0])
                || containsTypeVariables(TypeUtils.getImplicitUpperBounds(wild)[0]);
        }
        return false;
    }

    
Create a parameterized type instance.
Params:
raw – the raw class to create a parameterized type instance for
typeArguments – the types used for parameterization
Returns:
ParameterizedType
Since:
3.2/**
     * Create a parameterized type instance.
     *
     * @param raw the raw class to create a parameterized type instance for
     * @param typeArguments the types used for parameterization
     * @return {@link ParameterizedType}
     * @since 3.2
     */
    public static final ParameterizedType parameterize(final Class<?> raw, final Type... typeArguments) {
        return parameterizeWithOwner(null, raw, typeArguments);
    }

    
Create a parameterized type instance.
Params:
raw – the raw class to create a parameterized type instance for
typeArgMappings – the mapping used for parameterization
Returns:
ParameterizedType
Since:
3.2/**
     * Create a parameterized type instance.
     *
     * @param raw the raw class to create a parameterized type instance for
     * @param typeArgMappings the mapping used for parameterization
     * @return {@link ParameterizedType}
     * @since 3.2
     */
    public static final ParameterizedType parameterize(final Class<?> raw,
        final Map<TypeVariable<?>, Type> typeArgMappings) {
        Validate.notNull(raw, "raw class is null");
        Validate.notNull(typeArgMappings, "typeArgMappings is null");
        return parameterizeWithOwner(null, raw, extractTypeArgumentsFrom(typeArgMappings, raw.getTypeParameters()));
    }

    
Create a parameterized type instance.
Params:
owner – the owning type
raw – the raw class to create a parameterized type instance for
typeArguments – the types used for parameterization
Returns:
ParameterizedType
Since:
3.2/**
     * Create a parameterized type instance.
     *
     * @param owner the owning type
     * @param raw the raw class to create a parameterized type instance for
     * @param typeArguments the types used for parameterization
     *
     * @return {@link ParameterizedType}
     * @since 3.2
     */
    public static final ParameterizedType parameterizeWithOwner(final Type owner, final Class<?> raw,
        final Type... typeArguments) {
        Validate.notNull(raw, "raw class is null");
        final Type useOwner;
        if (raw.getEnclosingClass() == null) {
            Validate.isTrue(owner == null, "no owner allowed for top-level %s", raw);
            useOwner = null;
        } else if (owner == null) {
            useOwner = raw.getEnclosingClass();
        } else {
            Validate.isTrue(TypeUtils.isAssignable(owner, raw.getEnclosingClass()),
                "%s is invalid owner type for parameterized %s", owner, raw);
            useOwner = owner;
        }
        Validate.noNullElements(typeArguments, "null type argument at index %s");
        Validate.isTrue(raw.getTypeParameters().length == typeArguments.length,
            "invalid number of type parameters specified: expected %d, got %d", raw.getTypeParameters().length,
            typeArguments.length);

        return new ParameterizedTypeImpl(raw, useOwner, typeArguments);
    }

    
Create a parameterized type instance.
Params:
owner – the owning type
raw – the raw class to create a parameterized type instance for
typeArgMappings – the mapping used for parameterization
Returns:
ParameterizedType
Since:
3.2/**
     * Create a parameterized type instance.
     *
     * @param owner the owning type
     * @param raw the raw class to create a parameterized type instance for
     * @param typeArgMappings the mapping used for parameterization
     * @return {@link ParameterizedType}
     * @since 3.2
     */
    public static final ParameterizedType parameterizeWithOwner(final Type owner, final Class<?> raw,
        final Map<TypeVariable<?>, Type> typeArgMappings) {
        Validate.notNull(raw, "raw class is null");
        Validate.notNull(typeArgMappings, "typeArgMappings is null");
        return parameterizeWithOwner(owner, raw, extractTypeArgumentsFrom(typeArgMappings, raw.getTypeParameters()));
    }

    
Helper method to establish the formal parameters for a parameterized type.
Params:
mappings – map containing the assignments
variables – expected map keys
Returns:
array of map values corresponding to specified keys/**
     * Helper method to establish the formal parameters for a parameterized type.
     * @param mappings map containing the assignments
     * @param variables expected map keys
     * @return array of map values corresponding to specified keys
     */
    private static Type[] extractTypeArgumentsFrom(final Map<TypeVariable<?>, Type> mappings, final TypeVariable<?>[] variables) {
        final Type[] result = new Type[variables.length];
        int index = 0;
        for (final TypeVariable<?> var : variables) {
            Validate.isTrue(mappings.containsKey(var), "missing argument mapping for %s", toString(var));
            result[index++] = mappings.get(var);
        }
        return result;
    }

    
Get a WildcardTypeBuilder. 
Returns:
WildcardTypeBuilder
Since:
3.2/**
     * Get a {@link WildcardTypeBuilder}.
     * @return {@link WildcardTypeBuilder}
     * @since 3.2
     */
    public static WildcardTypeBuilder wildcardType() {
        return new WildcardTypeBuilder();
    }

    
Create a generic array type instance.
Params:
componentType – the type of the elements of the array. For example the component type of boolean[] is boolean
Returns:
GenericArrayType
Since:
3.2/**
     * Create a generic array type instance.
     *
     * @param componentType the type of the elements of the array. For example the component type of {@code boolean[]}
     *                      is {@code boolean}
     * @return {@link GenericArrayType}
     * @since 3.2
     */
    public static GenericArrayType genericArrayType(final Type componentType) {
        return new GenericArrayTypeImpl(Validate.notNull(componentType, "componentType is null"));
    }

    
Check equality of types.
Params:
t1 – the first type
t2 – the second type
Returns:
boolean
Since:
3.2/**
     * Check equality of types.
     *
     * @param t1 the first type
     * @param t2 the second type
     * @return boolean
     * @since 3.2
     */
    public static boolean equals(final Type t1, final Type t2) {
        if (Objects.equals(t1, t2)) {
            return true;
        }
        if (t1 instanceof ParameterizedType) {
            return equals((ParameterizedType) t1, t2);
        }
        if (t1 instanceof GenericArrayType) {
            return equals((GenericArrayType) t1, t2);
        }
        if (t1 instanceof WildcardType) {
            return equals((WildcardType) t1, t2);
        }
        return false;
    }

    
Learn whether t equals p. 
Params:
p – LHS
t – RHS
Returns:
boolean
Since:
3.2/**
     * Learn whether {@code t} equals {@code p}.
     * @param p LHS
     * @param t RHS
     * @return boolean
     * @since 3.2
     */
    private static boolean equals(final ParameterizedType p, final Type t) {
        if (t instanceof ParameterizedType) {
            final ParameterizedType other = (ParameterizedType) t;
            if (equals(p.getRawType(), other.getRawType()) && equals(p.getOwnerType(), other.getOwnerType())) {
                return equals(p.getActualTypeArguments(), other.getActualTypeArguments());
            }
        }
        return false;
    }

    
Learn whether t equals a. 
Params:
a – LHS
t – RHS
Returns:
boolean
Since:
3.2/**
     * Learn whether {@code t} equals {@code a}.
     * @param a LHS
     * @param t RHS
     * @return boolean
     * @since 3.2
     */
    private static boolean equals(final GenericArrayType a, final Type t) {
        return t instanceof GenericArrayType
            && equals(a.getGenericComponentType(), ((GenericArrayType) t).getGenericComponentType());
    }

    
Learn whether t equals w. 
Params:
w – LHS
t – RHS
Returns:
boolean
Since:
3.2/**
     * Learn whether {@code t} equals {@code w}.
     * @param w LHS
     * @param t RHS
     * @return boolean
     * @since 3.2
     */
    private static boolean equals(final WildcardType w, final Type t) {
        if (t instanceof WildcardType) {
            final WildcardType other = (WildcardType) t;
            return equals(getImplicitLowerBounds(w), getImplicitLowerBounds(other))
                && equals(getImplicitUpperBounds(w), getImplicitUpperBounds(other));
        }
        return false;
    }

    
Learn whether t1 equals t2. 
Params:
t1 – LHS
t2 – RHS
Returns:
boolean
Since:
3.2/**
     * Learn whether {@code t1} equals {@code t2}.
     * @param t1 LHS
     * @param t2 RHS
     * @return boolean
     * @since 3.2
     */
    private static boolean equals(final Type[] t1, final Type[] t2) {
        if (t1.length == t2.length) {
            for (int i = 0; i < t1.length; i++) {
                if (!equals(t1[i], t2[i])) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    
Present a given type as a Java-esque String.
Params:
type – the type to create a String representation for, not null
Returns:
String
Since:
3.2/**
     * Present a given type as a Java-esque String.
     *
     * @param type the type to create a String representation for, not {@code null}
     * @return String
     * @since 3.2
     */
    public static String toString(final Type type) {
        Validate.notNull(type);
        if (type instanceof Class<?>) {
            return classToString((Class<?>) type);
        }
        if (type instanceof ParameterizedType) {
            return parameterizedTypeToString((ParameterizedType) type);
        }
        if (type instanceof WildcardType) {
            return wildcardTypeToString((WildcardType) type);
        }
        if (type instanceof TypeVariable<?>) {
            return typeVariableToString((TypeVariable<?>) type);
        }
        if (type instanceof GenericArrayType) {
            return genericArrayTypeToString((GenericArrayType) type);
        }
        throw new IllegalArgumentException(ObjectUtils.identityToString(type));
    }

    
Format a TypeVariable including its GenericDeclaration. 
Params:
var – the type variable to create a String representation for, not null
Returns:
String
Since:
3.2/**
     * Format a {@link TypeVariable} including its {@link GenericDeclaration}.
     *
     * @param var the type variable to create a String representation for, not {@code null}
     * @return String
     * @since 3.2
     */
    public static String toLongString(final TypeVariable<?> var) {
        Validate.notNull(var, "var is null");
        final StringBuilder buf = new StringBuilder();
        final GenericDeclaration d = var.getGenericDeclaration();
        if (d instanceof Class<?>) {
            Class<?> c = (Class<?>) d;
            while (true) {
                if (c.getEnclosingClass() == null) {
                    buf.insert(0, c.getName());
                    break;
                }
                buf.insert(0, c.getSimpleName()).insert(0, '.');
                c = c.getEnclosingClass();
            }
        } else if (d instanceof Type) {// not possible as of now
            buf.append(toString((Type) d));
        } else {
            buf.append(d);
        }
        return buf.append(':').append(typeVariableToString(var)).toString();
    }

    
Wrap the specified Type in a Typed wrapper. 
Params:
type – to wrap
Type parameters:
<T> – inferred generic type
Returns:
Typed<T>
Since:
3.2/**
     * Wrap the specified {@link Type} in a {@link Typed} wrapper.
     *
     * @param <T> inferred generic type
     * @param type to wrap
     * @return Typed&lt;T&gt;
     * @since 3.2
     */
    public static <T> Typed<T> wrap(final Type type) {
        return new Typed<T>() {
            @Override
            public Type getType() {
                return type;
            }
        };
    }

    
Wrap the specified Class in a Typed wrapper. 
Params:
type – to wrap
Type parameters:
<T> – generic type
Returns:
Typed<T>
Since:
3.2/**
     * Wrap the specified {@link Class} in a {@link Typed} wrapper.
     *
     * @param <T> generic type
     * @param type to wrap
     * @return Typed&lt;T&gt;
     * @since 3.2
     */
    public static <T> Typed<T> wrap(final Class<T> type) {
        return TypeUtils.wrap((Type) type);
    }

    
Format a Class as a String. 
Params:
c – Class to format
Returns:
String
Since:
3.2/**
     * Format a {@link Class} as a {@link String}.
     * @param c {@code Class} to format
     * @return String
     * @since 3.2
     */
    private static String classToString(final Class<?> c) {
        if (c.isArray()) {
            return toString(c.getComponentType()) + "[]";
        }

        final StringBuilder buf = new StringBuilder();

        if (c.getEnclosingClass() != null) {
            buf.append(classToString(c.getEnclosingClass())).append('.').append(c.getSimpleName());
        } else {
            buf.append(c.getName());
        }
        if (c.getTypeParameters().length > 0) {
            buf.append('<');
            appendAllTo(buf, ", ", c.getTypeParameters());
            buf.append('>');
        }
        return buf.toString();
    }

    
Format a TypeVariable as a String. 
Params:
v – TypeVariable to format
Returns:
String
Since:
3.2/**
     * Format a {@link TypeVariable} as a {@link String}.
     * @param v {@code TypeVariable} to format
     * @return String
     * @since 3.2
     */
    private static String typeVariableToString(final TypeVariable<?> v) {
        final StringBuilder buf = new StringBuilder(v.getName());
        final Type[] bounds = v.getBounds();
        if (bounds.length > 0 && !(bounds.length == 1 && Object.class.equals(bounds[0]))) {
            buf.append(" extends ");
            appendAllTo(buf, " & ", v.getBounds());
        }
        return buf.toString();
    }

    
Format a ParameterizedType as a String. 
Params:
p – ParameterizedType to format
Returns:
String
Since:
3.2/**
     * Format a {@link ParameterizedType} as a {@link String}.
     * @param p {@code ParameterizedType} to format
     * @return String
     * @since 3.2
     */
    private static String parameterizedTypeToString(final ParameterizedType p) {
        final StringBuilder buf = new StringBuilder();

        final Type useOwner = p.getOwnerType();
        final Class<?> raw = (Class<?>) p.getRawType();

        if (useOwner == null) {
            buf.append(raw.getName());
        } else {
            if (useOwner instanceof Class<?>) {
                buf.append(((Class<?>) useOwner).getName());
            } else {
                buf.append(useOwner.toString());
            }
            buf.append('.').append(raw.getSimpleName());
        }

        final int[] recursiveTypeIndexes = findRecursiveTypes(p);

        if (recursiveTypeIndexes.length > 0) {
            appendRecursiveTypes(buf, recursiveTypeIndexes, p.getActualTypeArguments());
        } else {
            appendAllTo(buf.append('<'), ", ", p.getActualTypeArguments()).append('>');
        }

        return buf.toString();
    }

    private static void appendRecursiveTypes(final StringBuilder buf, final int[] recursiveTypeIndexes, final Type[] argumentTypes) {
        for (int i = 0; i < recursiveTypeIndexes.length; i++) {
            appendAllTo(buf.append('<'), ", ", argumentTypes[i].toString()).append('>');
        }

        final Type[] argumentsFiltered = ArrayUtils.removeAll(argumentTypes, recursiveTypeIndexes);

        if (argumentsFiltered.length > 0) {
            appendAllTo(buf.append('<'), ", ", argumentsFiltered).append('>');
        }
    }

    private static int[] findRecursiveTypes(final ParameterizedType p) {
        final Type[] filteredArgumentTypes = Arrays.copyOf(p.getActualTypeArguments(), p.getActualTypeArguments().length);
        int[] indexesToRemove = new int[] {};
        for (int i = 0; i < filteredArgumentTypes.length; i++) {
            if (filteredArgumentTypes[i] instanceof TypeVariable<?>) {
                if (containsVariableTypeSameParametrizedTypeBound(((TypeVariable<?>) filteredArgumentTypes[i]), p)) {
                    indexesToRemove = ArrayUtils.add(indexesToRemove, i);
                }
            }
        }
        return indexesToRemove;
    }

    private static boolean containsVariableTypeSameParametrizedTypeBound(final TypeVariable<?> typeVariable, final ParameterizedType p) {
        return ArrayUtils.contains(typeVariable.getBounds(), p);
    }

    
Format a WildcardType as a String. 
Params:
w – WildcardType to format
Returns:
String
Since:
3.2/**
     * Format a {@link WildcardType} as a {@link String}.
     * @param w {@code WildcardType} to format
     * @return String
     * @since 3.2
     */
    private static String wildcardTypeToString(final WildcardType w) {
        final StringBuilder buf = new StringBuilder().append('?');
        final Type[] lowerBounds = w.getLowerBounds();
        final Type[] upperBounds = w.getUpperBounds();
        if (lowerBounds.length > 1 || lowerBounds.length == 1 && lowerBounds[0] != null) {
            appendAllTo(buf.append(" super "), " & ", lowerBounds);
        } else if (upperBounds.length > 1 || upperBounds.length == 1 && !Object.class.equals(upperBounds[0])) {
            appendAllTo(buf.append(" extends "), " & ", upperBounds);
        }
        return buf.toString();
    }

    
Format a GenericArrayType as a String. 
Params:
g – GenericArrayType to format
Returns:
String
Since:
3.2/**
     * Format a {@link GenericArrayType} as a {@link String}.
     * @param g {@code GenericArrayType} to format
     * @return String
     * @since 3.2
     */
    private static String genericArrayTypeToString(final GenericArrayType g) {
        return String.format("%s[]", toString(g.getGenericComponentType()));
    }

    
Append types to buf with separator sep. 
Params:
buf – destination
sep – separator
types – to append
Returns:
buf
Since:
3.2/**
     * Append {@code types} to {@code buf} with separator {@code sep}.
     * @param buf destination
     * @param sep separator
     * @param types to append
     * @return {@code buf}
     * @since 3.2
     */
    private static <T> StringBuilder appendAllTo(final StringBuilder buf, final String sep, final T... types) {
        Validate.notEmpty(Validate.noNullElements(types));
        if (types.length > 0) {
            buf.append(toString(types[0]));
            for (int i = 1; i < types.length; i++) {
                buf.append(sep).append(toString(types[i]));
            }
        }
        return buf;
    }

    private static <T> String toString(final T object) {
        return object instanceof Type ? toString((Type) object) : object.toString();
    }

}