actitve-process/.svn/pristine/35/358520018367c5a77db34bea09083b1d8f3c7e07.svn-base

package com.chinacreator.process.util;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

public final class Objects {
    private Objects() {
        throw new AssertionError("No java.util.Objects instances for you!");
    }

    /**
     * Returns {@code true} if the arguments are equal to each other
     * and {@code false} otherwise.
     * Consequently, if both arguments are {@code null}, {@code true}
     * is returned and if exactly one argument is {@code null}, {@code
     * false} is returned.  Otherwise, equality is determined by using
     * the {@link Object#equals equals} method of the first
     * argument.
     *
     * @param a an object
     * @param b an object to be compared with {@code a} for equality
     * @return {@code true} if the arguments are equal to each other
     * and {@code false} otherwise
     * @see Object#equals(Object)
     */
    public static boolean equals(Object a, Object b) {
        return (a == b) || (a != null && a.equals(b));
    }

    /**
     * Returns {@code true} if the arguments are deeply equal to each other
     * and {@code false} otherwise.
     *
     * Two {@code null} values are deeply equal.  If both arguments are
     * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
     * Object[]) Arrays.deepEquals} is used to determine equality.
     * Otherwise, equality is determined by using the {@link
     * Object#equals equals} method of the first argument.
     *
     * @param a an object
     * @param b an object to be compared with {@code a} for deep equality
     * @return {@code true} if the arguments are deeply equal to each other
     * and {@code false} otherwise
     * @see Arrays#deepEquals(Object[], Object[])
     * @see Objects#equals(Object, Object)
     */
//    public static boolean deepEquals(Object a, Object b) {
//        if (a == b)
//            return true;
//        else if (a == null || b == null)
//            return false;
//        else
//            return Arrays.deepEquals0(a, b);
//    }

    /**
     * Returns the hash code of a non-{@code null} argument and 0 for
     * a {@code null} argument.
     *
     * @param o an object
     * @return the hash code of a non-{@code null} argument and 0 for
     * a {@code null} argument
     * @see Object#hashCode
     */
    public static int hashCode(Object o) {
        return o != null ? o.hashCode() : 0;
    }

    /**
     * Generates a hash code for a sequence of input values. The hash
     * code is generated as if all the input values were placed into an
     * array, and that array were hashed by calling {@link
     * Arrays#hashCode(Object[])}.
     *
     * <p>This method is useful for implementing {@link
     * Object#hashCode()} on objects containing multiple fields. For
     * example, if an object that has three fields, {@code x}, {@code
     * y}, and {@code z}, one could write:
     *
     * <blockquote><pre>
     * &#064;Override public int hashCode() {
     *     return Objects.hash(x, y, z);
     * }
     * </pre></blockquote>
     *
     * <b>Warning: When a single object reference is supplied, the returned
     * value does not equal the hash code of that object reference.</b> This
     * value can be computed by calling {@link #hashCode(Object)}.
     *
     * @param values the values to be hashed
     * @return a hash value of the sequence of input values
     * @see Arrays#hashCode(Object[])
     * @see List#hashCode
     */
    public static int hash(Object... values) {
        return Arrays.hashCode(values);
    }

    /**
     * Returns the result of calling {@code toString} for a non-{@code
     * null} argument and {@code "null"} for a {@code null} argument.
     *
     * @param o an object
     * @return the result of calling {@code toString} for a non-{@code
     * null} argument and {@code "null"} for a {@code null} argument
     * @see Object#toString
     * @see String#valueOf(Object)
     */
    public static String toString(Object o) {
        return String.valueOf(o);
    }

    /**
     * Returns the result of calling {@code toString} on the first
     * argument if the first argument is not {@code null} and returns
     * the second argument otherwise.
     *
     * @param o an object
     * @param nullDefault string to return if the first argument is
     *        {@code null}
     * @return the result of calling {@code toString} on the first
     * argument if it is not {@code null} and the second argument
     * otherwise.
     * @see Objects#toString(Object)
     */
    public static String toString(Object o, String nullDefault) {
        return (o != null) ? o.toString() : nullDefault;
    }

    /**
     * Returns 0 if the arguments are identical and {@code
     * c.compare(a, b)} otherwise.
     * Consequently, if both arguments are {@code null} 0
     * is returned.
     *
     * <p>Note that if one of the arguments is {@code null}, a {@code
     * NullPointerException} may or may not be thrown depending on
     * what ordering policy, if any, the {@link Comparator Comparator}
     * chooses to have for {@code null} values.
     *
     * @param <T> the type of the objects being compared
     * @param a an object
     * @param b an object to be compared with {@code a}
     * @param c the {@code Comparator} to compare the first two arguments
     * @return 0 if the arguments are identical and {@code
     * c.compare(a, b)} otherwise.
     * @see Comparable
     * @see Comparator
     */
    public static <T> int compare(T a, T b, Comparator<? super T> c) {
        return (a == b) ? 0 :  c.compare(a, b);
    }

    /**
     * Checks that the specified object reference is not {@code null}. This
     * method is designed primarily for doing parameter validation in methods
     * and constructors, as demonstrated below:
     * <blockquote><pre>
     * public Foo(Bar bar) {
     *     this.bar = Objects.requireNonNull(bar);
     * }
     * </pre></blockquote>
     *
     * @param obj the object reference to check for nullity
     * @param <T> the type of the reference
     * @return {@code obj} if not {@code null}
     * @throws NullPointerException if {@code obj} is {@code null}
     */
    public static <T> T requireNonNull(T obj) {
        if (obj == null)
            throw new NullPointerException();
        return obj;
    }

    /**
     * Checks that the specified object reference is not {@code null} and
     * throws a customized {@link NullPointerException} if it is. This method
     * is designed primarily for doing parameter validation in methods and
     * constructors with multiple parameters, as demonstrated below:
     * <blockquote><pre>
     * public Foo(Bar bar, Baz baz) {
     *     this.bar = Objects.requireNonNull(bar, "bar must not be null");
     *     this.baz = Objects.requireNonNull(baz, "baz must not be null");
     * }
     * </pre></blockquote>
     *
     * @param obj     the object reference to check for nullity
     * @param message detail message to be used in the event that a {@code
     *                NullPointerException} is thrown
     * @param <T> the type of the reference
     * @return {@code obj} if not {@code null}
     * @throws NullPointerException if {@code obj} is {@code null}
     */
    public static <T> T requireNonNull(T obj, String message) {
        if (obj == null)
            throw new NullPointerException(message);
        return obj;
    }
}