/*
 * @(#)Object.java	1.58 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.lang;

/**
 * Class <code>Object</code> is the root of the class hierarchy. 
 * Every class has <code>Object</code> as a superclass. All objects, 
 * including arrays, implement the methods of this class. 
 *
 * @author  unascribed
 * @version 1.58, 12/03/01
 * @see     java.lang.Class
 * @since   JDK1.0
 */
public class Object {
    /**
     * Returns a hash code value for the object. This method is 
     * supported for the benefit of hashtables such as those provided by 
     * <code>java.util.Hashtable</code>. 
     * <p>
     * The general contract of <code>hashCode</code> is: 
     * <ul>
     * <li>Whenever it is invoked on the same object more than once during 
     *     an execution of a Java application, the <tt>hashCode</tt> method 
     *     must consistently return the same integer, provided no information 
     *     used in <tt>equals</tt> comparisons on the object is modified.
     *     This integer need not remain consistent from one execution of an
     *     application to another execution of the same application. 
     * <li>If two objects are equal according to the <tt>equals(Object)</tt>
     *     method, then calling the <code>hashCode</code> method on each of 
     *     the two objects must produce the same integer result. 
     * <li>It is <em>not</em> required that if two objects are unequal 
     *     according to the {@link java.lang.Object#equals(java.lang.Object)} 
     *     method, then calling the <tt>hashCode</tt> method on each of the 
     *     two objects must produce distinct integer results.  However, the 
     *     programmer should be aware that producing distinct integer results 
     *     for unequal objects may improve the performance of hashtables.
     * </ul>
     * <p>
     * As much as is reasonably practical, the hashCode method defined by 
     * class <tt>Object</tt> does return distinct integers for distinct 
     * objects. (This is typically implemented by converting the internal 
     * address of the object into an integer, but this implementation 
     * technique is not required by the 
     * Java<font size="-2"><sup>TM</sup></font> programming language.)
     *
     * @return  a hash code value for this object.
     * @see     java.lang.Object#equals(java.lang.Object)
     * @see     java.util.Hashtable
     */
    public native int hashCode();

    /**
     * Indicates whether some other object is "equal to" this one.
     * <p>
     * The <code>equals</code> method implements an equivalence relation: 
     * <ul>
     * <li>It is <i>reflexive</i>: for any reference value <code>x</code>, 
     *     <code>x.equals(x)</code> should return <code>true</code>. 
     * <li>It is <i>symmetric</i>: for any reference values <code>x</code> and 
     *     <code>y</code>, <code>x.equals(y)</code> should return 
     *     <code>true</code> if and only if <code>y.equals(x)</code> returns 
     *     <code>true</code>. 
     * <li>It is <i>transitive</i>: for any reference values <code>x</code>, 
     *     <code>y</code>, and <code>z</code>, if <code>x.equals(y)</code>
     *     returns  <code>true</code> and <code>y.equals(z)</code> returns 
     *     <code>true</code>, then <code>x.equals(z)</code> should return 
     *     <code>true</code>. 
     * <li>It is <i>consistent</i>: for any reference values <code>x</code> 
     *     and <code>y</code>, multiple invocations of <tt>x.equals(y)</tt>
     *     consistently return <code>true</code> or consistently return 
     *     <code>false</code>, provided no information used in
     *     <code>equals</code> comparisons on the object is modified.
     * <li>For any non-null reference value <code>x</code>, 
     *     <code>x.equals(null)</code> should return <code>false</code>.
     * </ul>
     * <p>
     * The <tt>equals</tt> method for class <code>Object</code> implements 
     * the most discriminating possible equivalence relation on objects; 
     * that is, for any reference values <code>x</code> and <code>y</code>, 
     * this method returns <code>true</code> if and only if <code>x</code> and 
     * <code>y</code> refer to the same object (<code>x==y</code> has the 
     * value <code>true</code>).
     * <p>
     * Note that it is generally necessary to override the <tt>hashCode</tt>
     * method whenever this method is overridden, so as to maintain the
     * general contract for the <tt>hashCode</tt> method, which states
     * that equal objects must have equal hash codes. 
     *
     * @param   obj   the reference object with which to compare.
     * @return  <code>true</code> if this object is the same as the obj
     *          argument; <code>false</code> otherwise.
     * @see     #hashCode()
     * @see     java.util.Hashtable
     */
    public boolean equals(Object obj) {
	return (this == obj);
    }
}