libjava/classpath/gnu/java/util/prefs/MemoryBasedPreferences.java

   1 /* MemoryBasedPreferences - A Preference node which holds all entries in memory
   2    Copyright (C) 2001, 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 package gnu.java.util.prefs;
  39
  40 import java.util.HashMap;
  41
  42 import java.util.prefs.*;
  43
  44 /**
  45  * A Preference node which holds all entries in memory
  46  *
  47  * @author Mark Wielaard (mark@klomp.org)
  48  */
  49 public class MemoryBasedPreferences extends AbstractPreferences {
  50
  51     /** True if this is a preference node in the user tree, false otherwise. */
  52     private final boolean isUser;
  53
  54     /** Contains all the preference entries of this node. */
  55     private HashMap entries = new HashMap();
  56
  57     /**
  58      * Creates a new preferences node with the given name and parent.
  59      * When isUser is true it will be user node otherwise it will be a system
  60      * node. It will always set the <code>newNode</code> field to true
  61      * since there is no real backing store, so all nodes are new.
  62      */
  63     public MemoryBasedPreferences(MemoryBasedPreferences parent,
  64                                   String name,
  65                                   boolean isUser) {
  66         super(parent, name);
  67         this.isUser = isUser;
  68
  69         // Since we do not have a real backing store all nodes are new
  70         newNode = true;
  71     }
  72
  73     /**
  74      * Returns true if this node was created as a user node.
  75      */
  76     public boolean isUserNode() {
  77         return isUser;
  78     }
  79
  80     /**
  81      * Returns an empty array since all children names are always already
  82      * cached.
  83      */
  84     protected String[] childrenNamesSpi() throws BackingStoreException {
  85         return new String[0];
  86     }
  87
  88     /**
  89      * Returns a new node with the given name with as parent this node and
  90      * with the <code>isUser</code> flag set to the same value as this node.
  91      */
  92     protected AbstractPreferences childSpi(String childName) {
  93        return new MemoryBasedPreferences(this, childName, isUser);
  94     }
  95
  96     /**
  97      * Returns a (possibly empty) array of keys of the preferences entries of
  98      * this node.
  99      */
 100     protected String[] keysSpi() throws BackingStoreException {
 101         return (String[]) entries.keySet().toArray(new String[entries.size()]);
 102     }
 103
 104     /**
 105      * Returns the associated value from this nodes preferences entries or
 106      * null when the key has not been set.
 107      */
 108     protected String getSpi(String key) {
 109         return (String) entries.get(key);
 110     }
 111
 112     /**
 113      * Sets the value for the given key.
 114      */
 115     protected void putSpi(String key, String value) {
 116         entries.put(key, value);
 117     }
 118
 119     /**
 120      * Removes the entry with the given key.
 121      */
 122     protected void removeSpi(String key) {
 123         entries.remove(key);
 124     }
 125
 126     /**
 127      * Does nothing since we do not have any backing store.
 128      */
 129     protected void flushSpi() {
 130     }
 131
 132     /**
 133      * Does nothing since we do not have any backing store.
 134      */
 135     protected void syncSpi() {
 136     }
 137
 138     /**
 139      * Just removes the entries map of this node.
 140      */
 141     protected void removeNodeSpi() {
 142         entries = null;
 143     }
 144 }