1 /* Pair.java -- A heterogenous pair of objects. 2 Copyright (C) 2006 3 Free Software Foundation, Inc. 4 5 This file is part of GNU Classpath. 6 7 GNU Classpath is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 2, or (at your option) 10 any later version. 11 12 GNU Classpath is distributed in the hope that it will be useful, but 13 WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GNU Classpath; see the file COPYING. If not, write to the 19 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 20 02110-1301 USA. 21 22 Linking this library statically or dynamically with other modules is 23 making a combined work based on this library. Thus, the terms and 24 conditions of the GNU General Public License cover the whole 25 combination. 26 27 As a special exception, the copyright holders of this library give you 28 permission to link this library with independent modules to produce an 29 executable, regardless of the license terms of these independent 30 modules, and to copy and distribute the resulting executable under 31 terms of your choice, provided that you also meet, for each linked 32 independent module, the terms and conditions of the license of that 33 module. An independent module is a module which is not derived from 34 or based on this library. If you modify this library, you may extend 35 this exception to your version of the library, but you are not 36 obligated to do so. If you do not wish to do so, delete this 37 exception statement from your version. */ 38 39 40 package gnu.classpath; 41 42 /** 43 * A container for a pair of heterogenous objects. 44 * 45 * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 46 */ 47 public class Pair<A,B> 48 { 49 50 /** 51 * The left-hand side of the pair. 52 */ 53 private A left; 54 55 /** 56 * The right-hand side of the pair. 57 */ 58 private B right; 59 60 /** 61 * Constructs a new pair using the given left and 62 * right values. 63 * 64 * @param left the left-hand side of the pair. 65 * @param right the right-hand side of the pair. 66 */ Pair(A left, B right)67 public Pair(A left, B right) 68 { 69 this.left = left; 70 this.right = right; 71 } 72 73 /** 74 * Returns the left-hand side of the pair. 75 * 76 * @return the left-hand value. 77 */ getLeft()78 public A getLeft() 79 { 80 return left; 81 } 82 83 /** 84 * Returns the right-hand side of the pair. 85 * 86 * @return the right-hand value. 87 */ getRight()88 public B getRight() 89 { 90 return right; 91 } 92 93 /** 94 * Returns true if the specified object is also a 95 * pair with equivalent left and right values. 96 * 97 * @param obj the object to compare. 98 * @return true if the two are equal. 99 */ equals(Object obj)100 public boolean equals(Object obj) 101 { 102 if (obj instanceof Pair) 103 { 104 Pair<A,B> p = (Pair<A,B>) obj; 105 A lp = p.getLeft(); 106 B rp = p.getRight(); 107 return (lp == null ? left == null : lp.equals(left)) && 108 (rp == null ? right == null : rp.equals(right)); 109 } 110 return false; 111 } 112 113 /** 114 * Returns a hashcode for the pair, created by the 115 * summation of the hashcodes of the left and right 116 * hand values. 117 * 118 * @return a hashcode for the pair. 119 */ hashCode()120 public int hashCode() 121 { 122 return (left == null ? 0 : left.hashCode()) 123 + (right == null ? 0 : right.hashCode()); 124 } 125 126 } 127