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 */
013package org.jikesrvm.util;
014
015/**
016 * A hash set with entirely immutable buckets. It doesn't correctly support
017 * remove, so use with care.
018 */
019public final class ImmutableEntryHashSetRVM<T> extends AbstractHashSetRVM<T> {
020
021  static final class Bucket<T> extends AbstractBucket<T> {
022    private final T key;
023    private final AbstractBucket<T> next;
024
025    Bucket(T key, AbstractBucket<T> next) {
026      this.key = key;
027      this.next = next;
028    }
029
030    @Override
031    AbstractBucket<T> setNext(AbstractBucket<T> next) {
032      if (this.next == next) {
033        return this;
034      } else {
035        return new Bucket<T>(key, next);
036      }
037    }
038
039    @Override
040    AbstractBucket<T> getNext() {
041      return next;
042    }
043
044    @Override
045    T getKey() {
046      return key;
047    }
048  }
049
050  @Override
051  AbstractBucket<T> createNewBucket(T key, AbstractBucket<T> next) {
052    return new Bucket<T>(key, next);
053  }
054
055  public ImmutableEntryHashSetRVM() {
056    super(DEFAULT_SIZE);
057  }
058
059  public ImmutableEntryHashSetRVM(int size) {
060    super(size);
061  }
062
063  @Override
064  public void remove(T key) {
065    throw new UnsupportedOperationException();
066  }
067}