https://projects.eclipse.org/projects/ee4j.jersey/jersey-common: Jersey core common packages (Eclipse Foundation) 
/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed 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.glassfish.jersey.internal.guava;


Static convenience methods that help a method or constructor check whether it was invoked
correctly (whether its preconditions have been met). These methods generally accept a boolean expression which is expected to be true (or in the case of 
checkNotNull, an object reference which is expected to be non-null). When false (or null) is passed instead, the Preconditions method throws an unchecked exception, which helps the calling method communicate to its caller that that caller has made
a mistake. Example: 
 
<p>
  /**
   * Returns the positive square root of the given value.
   *
   * @throws IllegalArgumentException if the value is negative
   */
  public static double sqrt(double value) {
    Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
    // calculate the square root
  }
<p>
  void exampleBadCaller() {
    double d = sqrt(-1.0);
  }


 In this example, checkArgument throws an IllegalArgumentException to indicate that exampleBadCaller made an error in its call to sqrt. 


Warning about performance




The goal of this class is to improve readability of code, but in some circumstances this may
come at a significant performance cost. Remember that parameter values for message construction
must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even
when the precondition check then succeeds (as it should almost always do in production). In some
circumstances these wasted CPU cycles and allocations can add up to a real problem.
Performance-sensitive precondition checks can always be converted to the customary form:

 
  if (value < 0.0) {
    throw new IllegalArgumentException("negative value: " + value);
  }




Other types of preconditions




Not every type of precondition failure is supported by these methods. Continue to throw standard JDK exceptions such as NoSuchElementException or UnsupportedOperationException in the situations they are intended for. 


Non-preconditions




It is of course possible to use the methods of this class to check for invalid conditions
which are not the caller's fault. Doing so is not recommended because it is
misleading to future readers of the code and of stack traces. See
Conditional
failures explained in the Guava User Guide for more advice.



java.util.Objects.requireNonNull()




Projects which use org.glassfish.jersey.internal.guava.common should generally avoid the use of Objects.requireNonNull(Object). Instead, use whichever of checkNotNull(Object) or verifyNotNull.verifyNotNull(Object) is appropriate to the situation. (The same goes for the message-accepting overloads.) 


Only %s is supported




In Preconditions error message template strings, only the "%s" specifier is supported, not the full range of Formatter specifiers. 


More information




See the Guava User Guide on
using 
Preconditions.

Author:Kevin Bourrillion
Since:2.0 (imported from Google Collections Library)
/**
 * Static convenience methods that help a method or constructor check whether it was invoked
 * correctly (whether its <i>preconditions</i> have been met). These methods generally accept a
 * {@code boolean} expression which is expected to be {@code true} (or in the case of {@code
 * checkNotNull}, an object reference which is expected to be non-null). When {@code false} (or
 * {@code null}) is passed instead, the {@code Preconditions} method throws an unchecked exception,
 * which helps the calling method communicate to <i>its</i> caller that <i>that</i> caller has made
 * a mistake. Example: <pre>   {@code
 * <p>
 *   /**
 *    * Returns the positive square root of the given value.
 *    *
 *    * @throws IllegalArgumentException if the value is negative
 *    *}{@code /
 *   public static double sqrt(double value) {
 *     Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
 *     // calculate the square root
 *   }
 * <p>
 *   void exampleBadCaller() {
 *     double d = sqrt(-1.0);
 *   }}</pre>
 * <p>
 * In this example, {@code checkArgument} throws an {@code IllegalArgumentException} to indicate
 * that {@code exampleBadCaller} made an error in <i>its</i> call to {@code sqrt}.
 * <p>
 * <h3>Warning about performance</h3>
 * <p>
 * <p>The goal of this class is to improve readability of code, but in some circumstances this may
 * come at a significant performance cost. Remember that parameter values for message construction
 * must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even
 * when the precondition check then succeeds (as it should almost always do in production). In some
 * circumstances these wasted CPU cycles and allocations can add up to a real problem.
 * Performance-sensitive precondition checks can always be converted to the customary form:
 * <pre>   {@code
 *
 *   if (value < 0.0) {
 *     throw new IllegalArgumentException("negative value: " + value);
 *   }}</pre>
 * <p>
 * <h3>Other types of preconditions</h3>
 * <p>
 * <p>Not every type of precondition failure is supported by these methods. Continue to throw
 * standard JDK exceptions such as {@link java.util.NoSuchElementException} or {@link
 * UnsupportedOperationException} in the situations they are intended for.
 * <p>
 * <h3>Non-preconditions</h3>
 * <p>
 * <p>It is of course possible to use the methods of this class to check for invalid conditions
 * which are <i>not the caller's fault</i>. Doing so is <b>not recommended</b> because it is
 * misleading to future readers of the code and of stack traces. See
 * <a href="http://code.google.com/p/guava-libraries/wiki/ConditionalFailuresExplained">Conditional
 * failures explained</a> in the Guava User Guide for more advice.
 * <p>
 * <h3>{@code java.util.Objects.requireNonNull()}</h3>
 * <p>
 * <p>Projects which use {@code org.glassfish.jersey.internal.guava.common} should generally avoid the use of {@link
 * java.util.Objects#requireNonNull(Object)}. Instead, use whichever of {@link
 * #checkNotNull(Object)} or {@link Verify#verifyNotNull(Object)} is appropriate to the situation.
 * (The same goes for the message-accepting overloads.)
 * <p>
 * <h3>Only {@code %s} is supported</h3>
 * <p>
 * <p>In {@code Preconditions} error message template strings, only the {@code "%s"} specifier is
 * supported, not the full range of {@link java.util.Formatter} specifiers.
 * <p>
 * <h3>More information</h3>
 * <p>
 * <p>See the Guava User Guide on
 * <a href="http://code.google.com/p/guava-libraries/wiki/PreconditionsExplained">using {@code
 * Preconditions}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0 (imported from Google Collections Library)
 */
public final class Preconditions {
    private Preconditions() {
    }

    
Ensures the truth of an expression involving one or more parameters to the calling method.

Params:
  • expression – a boolean expression
Throws:
/**
     * Ensures the truth of an expression involving one or more parameters to the calling method.
     *
     * @param expression a boolean expression
     * @throws IllegalArgumentException if {@code expression} is false
     */
    public static void checkArgument(boolean expression) {
        if (!expression) {
            throw new IllegalArgumentException();
        }
    }

    
Ensures the truth of an expression involving one or more parameters to the calling method.

Params:
  • expression –   a boolean expression
  • errorMessage – the exception message to use if the check fails; will be converted to a string using String.valueOf(Object)
Throws:
/**
     * Ensures the truth of an expression involving one or more parameters to the calling method.
     *
     * @param expression   a boolean expression
     * @param errorMessage the exception message to use if the check fails; will be converted to a
     *                     string using {@link String#valueOf(Object)}
     * @throws IllegalArgumentException if {@code expression} is false
     */
    public static void checkArgument(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalArgumentException(String.valueOf(errorMessage));
        }
    }

    
Ensures the truth of an expression involving one or more parameters to the calling method.

Params:
  • expression –           a boolean expression
  • errorMessageTemplate – a template for the exception message should the check fail. The message is formed by replacing each %s placeholder in the template with an argument. These are matched by position - the first %s gets 
                            errorMessageArgs[0], etc. Unmatched arguments will be appended to the formatted message in square braces. Unmatched placeholders will be left as-is.
  • errorMessageArgs –  the arguments to be substituted into the message template. Arguments are converted to strings using String.valueOf(Object).
Throws:
/**
     * Ensures the truth of an expression involving one or more parameters to the calling method.
     *
     * @param expression           a boolean expression
     * @param errorMessageTemplate a template for the exception message should the check fail. The
     *                             message is formed by replacing each {@code %s} placeholder in the template with an
     *                             argument. These are matched by position - the first {@code %s} gets {@code
     *                             errorMessageArgs[0]}, etc.  Unmatched arguments will be appended to the formatted message
     *                             in square braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments
     *                             are converted to strings using {@link String#valueOf(Object)}.
     * @throws IllegalArgumentException if {@code expression} is false
     * @throws NullPointerException     if the check fails and either {@code errorMessageTemplate} or
     *                                  {@code errorMessageArgs} is null (don't let this happen)
     */
    public static void checkArgument(boolean expression,
                                     String errorMessageTemplate,
                                     Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
        }
    }

    
Ensures the truth of an expression involving the state of the calling instance, but not
involving any parameters to the calling method.

Params:
  • expression – a boolean expression
Throws:
/**
     * Ensures the truth of an expression involving the state of the calling instance, but not
     * involving any parameters to the calling method.
     *
     * @param expression a boolean expression
     * @throws IllegalStateException if {@code expression} is false
     */
    public static void checkState(boolean expression) {
        if (!expression) {
            throw new IllegalStateException();
        }
    }

    
Ensures the truth of an expression involving the state of the calling instance, but not
involving any parameters to the calling method.

Params:
  • expression –   a boolean expression
  • errorMessage – the exception message to use if the check fails; will be converted to a string using String.valueOf(Object)
Throws:
/**
     * Ensures the truth of an expression involving the state of the calling instance, but not
     * involving any parameters to the calling method.
     *
     * @param expression   a boolean expression
     * @param errorMessage the exception message to use if the check fails; will be converted to a
     *                     string using {@link String#valueOf(Object)}
     * @throws IllegalStateException if {@code expression} is false
     */
    public static void checkState(boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalStateException(String.valueOf(errorMessage));
        }
    }

    
Ensures the truth of an expression involving the state of the calling instance, but not
involving any parameters to the calling method.

Params:
  • expression –           a boolean expression
  • errorMessageTemplate – a template for the exception message should the check fail. The message is formed by replacing each %s placeholder in the template with an argument. These are matched by position - the first %s gets 
                            errorMessageArgs[0], etc. Unmatched arguments will be appended to the formatted message in square braces. Unmatched placeholders will be left as-is.
  • errorMessageArgs –  the arguments to be substituted into the message template. Arguments are converted to strings using String.valueOf(Object).
Throws:
/**
     * Ensures the truth of an expression involving the state of the calling instance, but not
     * involving any parameters to the calling method.
     *
     * @param expression           a boolean expression
     * @param errorMessageTemplate a template for the exception message should the check fail. The
     *                             message is formed by replacing each {@code %s} placeholder in the template with an
     *                             argument. These are matched by position - the first {@code %s} gets {@code
     *                             errorMessageArgs[0]}, etc.  Unmatched arguments will be appended to the formatted message
     *                             in square braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments
     *                             are converted to strings using {@link String#valueOf(Object)}.
     * @throws IllegalStateException if {@code expression} is false
     * @throws NullPointerException  if the check fails and either {@code errorMessageTemplate} or
     *                               {@code errorMessageArgs} is null (don't let this happen)
     */
    public static void checkState(boolean expression,
                                  String errorMessageTemplate,
                                  Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
        }
    }

    
Ensures that an object reference passed as a parameter to the calling method is not null.

Params:
  • reference – an object reference
Throws:
Returns:the non-null reference that was validated
/**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference an object reference
     * @return the non-null reference that was validated
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull(T reference) {
        if (reference == null) {
            throw new NullPointerException();
        }
        return reference;
    }

    
Ensures that an object reference passed as a parameter to the calling method is not null.

Params:
  • reference –    an object reference
  • errorMessage – the exception message to use if the check fails; will be converted to a string using String.valueOf(Object)
Throws:
Returns:the non-null reference that was validated
/**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference    an object reference
     * @param errorMessage the exception message to use if the check fails; will be converted to a
     *                     string using {@link String#valueOf(Object)}
     * @return the non-null reference that was validated
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull(T reference, Object errorMessage) {
        if (reference == null) {
            throw new NullPointerException(String.valueOf(errorMessage));
        }
        return reference;
    }

    
Ensures that an object reference passed as a parameter to the calling method is not null.

Params:
  • reference –            an object reference
  • errorMessageTemplate – a template for the exception message should the check fail. The message is formed by replacing each %s placeholder in the template with an argument. These are matched by position - the first %s gets 
                            errorMessageArgs[0], etc. Unmatched arguments will be appended to the formatted message in square braces. Unmatched placeholders will be left as-is.
  • errorMessageArgs –  the arguments to be substituted into the message template. Arguments are converted to strings using String.valueOf(Object).
Throws:
Returns:the non-null reference that was validated
/**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference            an object reference
     * @param errorMessageTemplate a template for the exception message should the check fail. The
     *                             message is formed by replacing each {@code %s} placeholder in the template with an
     *                             argument. These are matched by position - the first {@code %s} gets {@code
     *                             errorMessageArgs[0]}, etc.  Unmatched arguments will be appended to the formatted message
     *                             in square braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments
     *                             are converted to strings using {@link String#valueOf(Object)}.
     * @return the non-null reference that was validated
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull(T reference,
                                     String errorMessageTemplate,
                                     Object... errorMessageArgs) {
        if (reference == null) {
            // If either of these parameters is null, the right thing happens anyway
            throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
        }
        return reference;
    }

  /*
   * All recent hotspots (as of 2009) *really* like to have the natural code
   *
   * if (guardExpression) {
   *    throw new BadException(messageExpression);
   * }
   *
   * refactored so that messageExpression is moved to a separate String-returning method.
   *
   * if (guardExpression) {
   *    throw new BadException(badMsg(...));
   * }
   *
   * The alternative natural refactorings into void or Exception-returning methods are much slower.
   * This is a big deal - we're talking factors of 2-8 in microbenchmarks, not just 10-20%.  (This
   * is a hotspot optimizer bug, which should be fixed, but that's a separate, big project).
   *
   * The coding pattern above is heavily used in java.util, e.g. in ArrayList.  There is a
   * RangeCheckMicroBenchmark in the JDK that was used to test this.
   *
   * But the methods in this class want to throw different exceptions, depending on the args, so it
   * appears that this pattern is not directly applicable.  But we can use the ridiculous, devious
   * trick of throwing an exception in the middle of the construction of another exception.  Hotspot
   * is fine with that.
   */

    
Ensures that index specifies a valid element in an array, list or string of size size. An element index may range from zero, inclusive, to size, exclusive. 
Params:
  • index – a user-supplied index identifying an element of an array, list or string
  • size –  the size of that array, list or string
Throws:
Returns:the value of index
/**
     * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
     * {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
     *
     * @param index a user-supplied index identifying an element of an array, list or string
     * @param size  the size of that array, list or string
     * @return the value of {@code index}
     * @throws IndexOutOfBoundsException if {@code index} is negative or is not less than {@code size}
     * @throws IllegalArgumentException  if {@code size} is negative
     */
    public static int checkElementIndex(int index, int size) {
        return checkElementIndex(index, size, "index");
    }

    
Ensures that index specifies a valid element in an array, list or string of size size. An element index may range from zero, inclusive, to size, exclusive. 
Params:
  • index – a user-supplied index identifying an element of an array, list or string
  • size –  the size of that array, list or string
  • desc –  the text to use to describe this index in an error message
Throws:
Returns:the value of index
/**
     * Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
     * {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
     *
     * @param index a user-supplied index identifying an element of an array, list or string
     * @param size  the size of that array, list or string
     * @param desc  the text to use to describe this index in an error message
     * @return the value of {@code index}
     * @throws IndexOutOfBoundsException if {@code index} is negative or is not less than {@code size}
     * @throws IllegalArgumentException  if {@code size} is negative
     */
    private static int checkElementIndex(
            int index, int size, String desc) {
        // Carefully optimized for execution by hotspot (explanatory comment above)
        if (index < 0 || index >= size) {
            throw new IndexOutOfBoundsException(badElementIndex(index, size, desc));
        }
        return index;
    }

    private static String badElementIndex(int index, int size, String desc) {
        if (index < 0) {
            return format("%s (%s) must not be negative", desc, index);
        } else if (size < 0) {
            throw new IllegalArgumentException("negative size: " + size);
        } else { // index >= size
            return format("%s (%s) must be less than size (%s)", desc, index, size);
        }
    }

    
Ensures that index specifies a valid position in an array, list or string of size size. A position index may range from zero to size, inclusive. 
Params:
  • index – a user-supplied index identifying a position in an array, list or string
  • size –  the size of that array, list or string
Throws:
Returns:the value of index
/**
     * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
     * size {@code size}. A position index may range from zero to {@code size}, inclusive.
     *
     * @param index a user-supplied index identifying a position in an array, list or string
     * @param size  the size of that array, list or string
     * @return the value of {@code index}
     * @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
     * @throws IllegalArgumentException  if {@code size} is negative
     */
    public static int checkPositionIndex(int index, int size) {
        return checkPositionIndex(index, size, "index");
    }

    
Ensures that index specifies a valid position in an array, list or string of size size. A position index may range from zero to size, inclusive. 
Params:
  • index – a user-supplied index identifying a position in an array, list or string
  • size –  the size of that array, list or string
  • desc –  the text to use to describe this index in an error message
Throws:
Returns:the value of index
/**
     * Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
     * size {@code size}. A position index may range from zero to {@code size}, inclusive.
     *
     * @param index a user-supplied index identifying a position in an array, list or string
     * @param size  the size of that array, list or string
     * @param desc  the text to use to describe this index in an error message
     * @return the value of {@code index}
     * @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
     * @throws IllegalArgumentException  if {@code size} is negative
     */
    private static int checkPositionIndex(int index, int size, String desc) {
        // Carefully optimized for execution by hotspot (explanatory comment above)
        if (index < 0 || index > size) {
            throw new IndexOutOfBoundsException(badPositionIndex(index, size, desc));
        }
        return index;
    }

    private static String badPositionIndex(int index, int size, String desc) {
        if (index < 0) {
            return format("%s (%s) must not be negative", desc, index);
        } else if (size < 0) {
            throw new IllegalArgumentException("negative size: " + size);
        } else { // index > size
            return format("%s (%s) must not be greater than size (%s)", desc, index, size);
        }
    }

    
Ensures that start and end specify a valid positions in an array, list or string of size size, and are in order. A position index may range from zero to size, inclusive. 
Params:
  • start – a user-supplied index identifying a starting position in an array, list or string
  • end –   a user-supplied index identifying a ending position in an array, list or string
  • size –  the size of that array, list or string
Throws:
/**
     * Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in an array, list
     * or string of size {@code size}, and are in order. A position index may range from zero to
     * {@code size}, inclusive.
     *
     * @param start a user-supplied index identifying a starting position in an array, list or string
     * @param end   a user-supplied index identifying a ending position in an array, list or string
     * @param size  the size of that array, list or string
     * @throws IndexOutOfBoundsException if either index is negative or is greater than {@code size},
     *                                   or if {@code end} is less than {@code start}
     * @throws IllegalArgumentException  if {@code size} is negative
     */
    public static void checkPositionIndexes(int start, int end, int size) {
        // Carefully optimized for execution by hotspot (explanatory comment above)
        if (start < 0 || end < start || end > size) {
            throw new IndexOutOfBoundsException(badPositionIndexes(start, end, size));
        }
    }

    private static String badPositionIndexes(int start, int end, int size) {
        if (start < 0 || start > size) {
            return badPositionIndex(start, size, "start index");
        }
        if (end < 0 || end > size) {
            return badPositionIndex(end, size, "end index");
        }
        // end < start
        return format("end index (%s) must not be less than start index (%s)", end, start);
    }

    
Substitutes each %s in template with an argument. These are matched by position: the first %s gets args[0], etc. If there are more arguments than placeholders, the unmatched arguments will be appended to the end of the formatted message in square braces. 
Params:
  • template – a non-null string containing 0 or more %s placeholders.
  • args –  the arguments to be substituted into the message template. Arguments are converted to strings using String.valueOf(Object). Arguments can be null.
/**
     * Substitutes each {@code %s} in {@code template} with an argument. These are matched by
     * position: the first {@code %s} gets {@code args[0]}, etc.  If there are more arguments than
     * placeholders, the unmatched arguments will be appended to the end of the formatted message in
     * square braces.
     *
     * @param template a non-null string containing 0 or more {@code %s} placeholders.
     * @param args     the arguments to be substituted into the message template. Arguments are converted
     *                 to strings using {@link String#valueOf(Object)}. Arguments can be null.
     */
    // Note that this is somewhat-improperly used from Verify.java as well.
    private static String format(String template, Object... args) {
        template = String.valueOf(template); // null -> "null"

        // start substituting the arguments into the '%s' placeholders
        StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
        int templateStart = 0;
        int i = 0;
        while (i < args.length) {
            int placeholderStart = template.indexOf("%s", templateStart);
            if (placeholderStart == -1) {
                break;
            }
            builder.append(template.substring(templateStart, placeholderStart));
            builder.append(args[i++]);
            templateStart = placeholderStart + 2;
        }
        builder.append(template.substring(templateStart));

        // if we run out of placeholders, append the extra args in square braces
        if (i < args.length) {
            builder.append(" [");
            builder.append(args[i++]);
            while (i < args.length) {
                builder.append(", ");
                builder.append(args[i++]);
            }
            builder.append(']');
        }

        return builder.toString();
    }
}