Source for gnu.classpath.Pair

   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:    */
  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:    */
  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:    */
  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:    */
 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:    */
 120:   public int hashCode()
 121:   {
 122:     return (left == null ? 0 : left.hashCode())
 123:       + (right == null ? 0 : right.hashCode());
 124:   }
 125: 
 126: }