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        AbstractBucket<K, V> getNext() {
034          return next;
035        }
036    
037        AbstractBucket<K, V> setNext(AbstractBucket<K, V> n) {
038          if (next == n) {
039            return this;
040          } else {
041            return new Bucket<K, V>(key, value, n);
042          }
043        }
044    
045        K getKey() {
046          return key;
047        }
048    
049        V getValue() {
050          return value;
051        }
052    
053        void setValue(V v) {
054          throw new UnsupportedOperationException();
055        }
056      }
057    
058      @Override
059      AbstractBucket<K,V> createNewBucket(K key, V value, AbstractBucket<K, V> next) {
060        return new Bucket<K,V>(key, value, next);
061      }
062    
063      public ImmutableEntryHashMapRVM() {
064        super(DEFAULT_SIZE);
065      }
066    
067      public ImmutableEntryHashMapRVM(int size) {
068        super(size);
069      }
070    
071      public V remove(K key) {
072        throw new UnsupportedOperationException();
073      }
074    
075      @Override
076      protected boolean same(K k1, K k2) {
077        return k1.equals(k2);
078      }
079    
080      @Override
081      protected int hashTheKey(K key) {
082        return key.hashCode();
083      }
084    }