Source for gnu.java.rmi.activation.BidiTable

   1: /* BidiHasthable.java -- Bidirectional hash table.
   2:    Copyright (C) 2006 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package gnu.java.rmi.activation;
  40: 
  41: import java.util.Collection;
  42: import java.util.HashMap;
  43: import java.util.Iterator;
  44: import java.util.Map;
  45: 
  46: /**
  47:  * The bidirectional hash table, maps both a to b and b to a.
  48:  *
  49:  * @author Audrius Meskauskas (audriusa@bioinformatics.org)
  50:  */
  51: public class BidiTable
  52: {
  53:   /**
  54:    * Use serialVerionUID for interoperability.
  55:    */
  56:   private static final long serialVersionUID = 1;
  57: 
  58:   /**
  59:    * Maps keys to values
  60:    */
  61:   protected Map k2v;
  62: 
  63:   /**
  64:    * Maps values to keys (in reverse)
  65:    */
  66:   protected Map v2k;
  67: 
  68:   /**
  69:    * Create a new table that is ready to use.
  70:    */
  71:   public BidiTable()
  72:   {
  73:     k2v = new HashMap();
  74:     v2k = new HashMap();
  75:   }
  76: 
  77:   /**
  78:    * Create a new instance where the hashtable fields are not initialised
  79:    * (called from derivatives that intialise hashtables in they own way.
  80:    *
  81:    * @param flags currently used to mark the different constructor only.
  82:    */
  83:   protected BidiTable(int flags)
  84:   {
  85:   }
  86: 
  87:   /**
  88:    * Get key by value
  89:    */
  90:   public synchronized Object getKey(Object value)
  91:   {
  92:     return v2k.get(value);
  93:   }
  94: 
  95:   /**
  96:    * Put key-value pair.
  97:    */
  98:   public synchronized void put(Object key, Object value)
  99:   {
 100:     k2v.put(key, value);
 101:     v2k.put(value, key);
 102:   }
 103: 
 104:   /**
 105:    * Get value from key
 106:    */
 107:   public synchronized Object get(Object key)
 108:   {
 109:     return k2v.get(key);
 110:   }
 111: 
 112:   /**
 113:    * Remove the key-value pair by key
 114:    */
 115:   public synchronized void removeKey(Object key)
 116:   {
 117:     Object value = k2v.get(key);
 118:     if (value!=null)
 119:       {
 120:         k2v.remove(key);
 121:         v2k.remove(value);
 122:       }
 123:   }
 124: 
 125:   /**
 126:    * Check if the table contains this key.
 127:    */
 128:   public synchronized boolean containsKey(Object key)
 129:   {
 130:     return k2v.containsKey(key);
 131:   }
 132: 
 133:   /**
 134:    * This method is called before exit and may be used to write the database
 135:    * to the disk. The default method does nothing.
 136:    */
 137:   public synchronized void shutdown()
 138:   {
 139:   }
 140: 
 141:   /**
 142:    * Get the size.
 143:    */
 144:   public synchronized int size()
 145:   {
 146:     return k2v.size();
 147:   }
 148: 
 149:   /**
 150:    * Get the key collection.
 151:    */
 152:   public synchronized Object[] keys()
 153:   {
 154:     Collection keys = k2v.keySet();
 155:     Object[] k = new Object[keys.size()];
 156: 
 157:     Iterator iter = keys.iterator();
 158:     for (int i = 0; i < k.length; i++)
 159:       k[i] = iter.next();
 160: 
 161:     return k;
 162:   }
 163: }