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package java.util;

/**
 * Backport of {@code java.util.Objects#hash(Object...)} and {@code java.util.Objects#hashCode()} from Java 7 into Java 6.
 * 
 * @author Markus KARG ([email protected])
 */
public final class Objects {
	/**
	 * 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[])}.
	 * 
	 * 
	 * 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:
	 * 
	 * 

	 * 
	 * 	 * @Override
	 * public int hashCode() {
	 * 	return Objects.hash(x, y, z);
	 * }
	 * 
	 * 
	 * 
	 * 
	 * @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 final int hash(final Object... values) {
		return Arrays.hashCode(values);
	}

	/**
	 * 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 final int hashCode(final Object o) {
		return o != null ? o.hashCode() : 0;
	}

	/**
	 * 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 final boolean equals(final Object a, final Object b) {
		return (a == b) || (a != null && a.equals(b));
	}
}