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.compilers.opt.util;
014
015import java.util.Enumeration;
016import java.util.NoSuchElementException;
017
018/**
019 * A <code>FilterEnumerator</code> filters and maps a source
020 * <code>Enumeration</code> to generate a new one.
021 */
022public class FilterEnumerator<S, T> implements Enumeration<T> {
023  final Enumeration<S> e;
024  final Filter<S, T> f;
025  private S next;
026  private boolean done;
027
028  public FilterEnumerator(Enumeration<S> e, Filter<S, T> f) {
029    this.e = e;
030    this.f = f;
031    advance();
032  }
033
034  private void advance() {
035    while (e.hasMoreElements()) {
036      next = e.nextElement();
037      if (f.isElement(next)) {
038        return;
039      }
040    }
041    done = true;
042  }
043
044  @Override
045  public T nextElement() {
046    if (done) {
047      throw new NoSuchElementException();
048    }
049    S o = next;
050    advance();
051    return f.map(o);
052  }
053
054  @Override
055  public boolean hasMoreElements() {
056    return !done;
057  }
058
059  public static class Filter<S, T> {                  // override with your mapping.
060
061    public boolean isElement(S o) {
062      return true;
063    }
064
065    @SuppressWarnings("unchecked")
066    public T map(S o) {
067      return (T) o;
068    }
069  }
070}