001    /*
002     *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003     *
004     *  This file is licensed to You under the Eclipse Public License (EPL);
005     *  You may not use this file except in compliance with the License. You
006     *  may obtain a copy of the License at
007     *
008     *      http://www.opensource.org/licenses/eclipse-1.0.php
009     *
010     *  See the COPYRIGHT.txt file distributed with this work for information
011     *  regarding copyright ownership.
012     */
013    package org.jikesrvm.util;
014    
015    /**
016     * A hash map with entirely immutable buckets. It doesn't correctly support
017     * remove, and its values cannot be mutated by a put with the same key - use
018     * with care.
019     */
020    public final class ImmutableEntryHashMapRVM<K, V> extends AbstractHashMapRVM<K,V> {
021    
022      static final class Bucket<K, V> extends AbstractBucket<K,V> {
023        private final AbstractBucket<K, V> next;
024        private final K key;
025        private final V value;
026    
027        Bucket(K k, V v, AbstractBucket<K, V> n) {
028          key = k;
029          value = v;
030          next = n;
031        }
032    
033        @Override
034        AbstractBucket<K, V> getNext() {
035          return next;
036        }
037    
038        @Override
039        AbstractBucket<K, V> setNext(AbstractBucket<K, V> n) {
040          if (next == n) {
041            return this;
042          } else {
043            return new Bucket<K, V>(key, value, n);
044          }
045        }
046    
047        @Override
048        K getKey() {
049          return key;
050        }
051    
052        @Override
053        V getValue() {
054          return value;
055        }
056    
057        @Override
058        void setValue(V v) {
059          throw new UnsupportedOperationException();
060        }
061      }
062    
063      @Override
064      AbstractBucket<K,V> createNewBucket(K key, V value, AbstractBucket<K, V> next) {
065        return new Bucket<K,V>(key, value, next);
066      }
067    
068      public ImmutableEntryHashMapRVM() {
069        super(DEFAULT_SIZE);
070      }
071    
072      public ImmutableEntryHashMapRVM(int size) {
073        super(size);
074      }
075    
076      @Override
077      public V remove(K key) {
078        throw new UnsupportedOperationException();
079      }
080    
081      @Override
082      protected boolean same(K k1, K k2) {
083        return k1.equals(k2);
084      }
085    
086      @Override
087      protected int hashTheKey(K key) {
088        return key.hashCode();
089      }
090    }