/*
 * 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.tuple;

An immutable pair consisting of two Object elements.
Although the implementation is immutable, there is no restriction on the objects that may be stored. If mutable objects are stored in the pair, then the pair itself effectively becomes mutable. The class is also final, so a subclass can not add undesirable behaviour.
#ThreadSafe# if both paired objects are thread-safe
Type parameters:
<L> – the left element type
<R> – the right element type
Since:
Lang 3.0/**
 * <p>An immutable pair consisting of two {@code Object} elements.</p>
 *
 * <p>Although the implementation is immutable, there is no restriction on the objects
 * that may be stored. If mutable objects are stored in the pair, then the pair
 * itself effectively becomes mutable. The class is also {@code final}, so a subclass
 * can not add undesirable behaviour.</p>
 *
 * <p>#ThreadSafe# if both paired objects are thread-safe</p>
 *
 * @param <L> the left element type
 * @param <R> the right element type
 *
 * @since Lang 3.0
 */
public final class ImmutablePair<L, R> extends Pair<L, R> {

    
An immutable pair of nulls.
/**
     * An immutable pair of nulls.
     */
    // This is not defined with generics to avoid warnings in call sites.
    @SuppressWarnings("rawtypes")
    private static final ImmutablePair NULL = ImmutablePair.of(null, null);

    
Serialization version /** Serialization version */
    private static final long serialVersionUID = 4954918890077093841L;

    
Returns an immutable pair of nulls.
Type parameters:
<L> – the left element of this pair. Value is null.
<R> – the right element of this pair. Value is null.
Returns:
an immutable pair of nulls.
Since:
3.6/**
     * Returns an immutable pair of nulls.
     *
     * @param <L> the left element of this pair. Value is {@code null}.
     * @param <R> the right element of this pair. Value is {@code null}.
     * @return an immutable pair of nulls.
     * @since 3.6
     */
    @SuppressWarnings("unchecked")
    public static <L, R> ImmutablePair<L, R> nullPair() {
        return NULL;
    }

    
Left object /** Left object */
    public final L left;
    
Right object /** Right object */
    public final R right;

    
Obtains an immutable pair of from two objects inferring the generic types.
This factory allows the pair to be created using inference to
obtain the generic types.
Params:
left –  the left element, may be null
right –  the right element, may be null
Type parameters:
<L> – the left element type
<R> – the right element type
Returns:
a pair formed from the two parameters, not null/**
     * <p>Obtains an immutable pair of from two objects inferring the generic types.</p>
     *
     * <p>This factory allows the pair to be created using inference to
     * obtain the generic types.</p>
     *
     * @param <L> the left element type
     * @param <R> the right element type
     * @param left  the left element, may be null
     * @param right  the right element, may be null
     * @return a pair formed from the two parameters, not null
     */
    public static <L, R> ImmutablePair<L, R> of(final L left, final R right) {
        return new ImmutablePair<>(left, right);
    }

    
Create a new pair instance.
Params:
left –  the left value, may be null
right –  the right value, may be null/**
     * Create a new pair instance.
     *
     * @param left  the left value, may be null
     * @param right  the right value, may be null
     */
    public ImmutablePair(final L left, final R right) {
        super();
        this.left = left;
        this.right = right;
    }

    //-----------------------------------------------------------------------
    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public L getLeft() {
        return left;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public R getRight() {
        return right;
    }

    
Throws UnsupportedOperationException.
This pair is immutable, so this operation is not supported.
Params:
value –  the value to set
Throws:
UnsupportedOperationException – as this operation is not supported
Returns:
never/**
     * <p>Throws {@code UnsupportedOperationException}.</p>
     *
     * <p>This pair is immutable, so this operation is not supported.</p>
     *
     * @param value  the value to set
     * @return never
     * @throws UnsupportedOperationException as this operation is not supported
     */
    @Override
    public R setValue(final R value) {
        throw new UnsupportedOperationException();
    }

}