001    /*
002     * Copyright 1999-2005 Sun Microsystems, Inc.  All Rights Reserved.
003     * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004     *
005     * This code is free software; you can redistribute it and/or modify it
006     * under the terms of the GNU General Public License version 2 only, as
007     * published by the Free Software Foundation.  Sun designates this
008     * particular file as subject to the "Classpath" exception as provided
009     * by Sun in the LICENSE file that accompanied this code.
010     *
011     * This code is distributed in the hope that it will be useful, but WITHOUT
012     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013     * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
014     * version 2 for more details (a copy is included in the LICENSE file that
015     * accompanied this code).
016     *
017     * You should have received a copy of the GNU General Public License version
018     * 2 along with this work; if not, write to the Free Software Foundation,
019     * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020     *
021     * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022     * CA 95054 USA or visit www.sun.com if you need additional information or
023     * have any questions.
024     */
025    
026    package com.sun.tools.javac.util;
027    
028    /** A generic class for pairs.
029     *
030     *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
031     *  you write code that depends on this, you do so at your own risk.
032     *  This code and its internal interfaces are subject to change or
033     *  deletion without notice.</b>
034     */
035    public class Pair<A, B> {
036    
037        public final A fst;
038        public final B snd;
039    
040        public Pair(A fst, B snd) {
041            this.fst = fst;
042            this.snd = snd;
043        }
044    
045        public String toString() {
046            return "Pair[" + fst + "," + snd + "]";
047        }
048    
049        private static boolean equals(Object x, Object y) {
050            return (x == null && y == null) || (x != null && x.equals(y));
051        }
052    
053        public boolean equals(Object other) {
054            return
055                other instanceof Pair<?,?> &&
056                equals(fst, ((Pair<?,?>)other).fst) &&
057                equals(snd, ((Pair<?,?>)other).snd);
058        }
059    
060        public int hashCode() {
061            if (fst == null) return (snd == null) ? 0 : snd.hashCode() + 1;
062            else if (snd == null) return fst.hashCode() + 2;
063            else return fst.hashCode() * 17 + snd.hashCode();
064        }
065    
066        public static <A,B> Pair<A,B> of(A a, B b) {
067            return new Pair<A,B>(a,b);
068        }
069    }