1/*
2 * Copyright (C) 2012 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import static com.google.common.base.Preconditions.checkNotNull;
20
21import com.google.common.annotations.GwtCompatible;
22
23import java.util.Iterator;
24
25/**
26 * An iterator that transforms a backing iterator; for internal use. This avoids
27 * the object overhead of constructing a {@link Function} for internal methods.
28 *
29 * @author Louis Wasserman
30 */
31@GwtCompatible
32abstract class TransformedIterator<F, T> implements Iterator<T> {
33  final Iterator<? extends F> backingIterator;
34
35  TransformedIterator(Iterator<? extends F> backingIterator) {
36    this.backingIterator = checkNotNull(backingIterator);
37  }
38
39  abstract T transform(F from);
40
41  @Override
42  public final boolean hasNext() {
43    return backingIterator.hasNext();
44  }
45
46  @Override
47  public final T next() {
48    return transform(backingIterator.next());
49  }
50
51  @Override
52  public final void remove() {
53    backingIterator.remove();
54  }
55}
56