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