1 /*
2 * Copyright (C) 2007 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
17 package com.google.common.collect;
18
19 import com.google.common.annotations.GwtCompatible;
20 import com.google.errorprone.annotations.CanIgnoreReturnValue;
21 import java.util.Iterator;
22
23 /**
24 * An iterator which forwards all its method calls to another iterator. Subclasses should override
25 * one or more methods to modify the behavior of the backing iterator as desired per the <a
26 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
27 *
28 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
29 * default} methods. Specifically, it forwards calls only for methods that existed <a
30 * href="https://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html">before {@code default}
31 * methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it inherits their
32 * default implementations. When those implementations invoke methods, they invoke methods on the
33 * {@code ForwardingIterator}.
34 *
35 * @author Kevin Bourrillion
36 * @since 2.0
37 */
38 @GwtCompatible
39 public abstract class ForwardingIterator<T> extends ForwardingObject implements Iterator<T> {
40
41 /** Constructor for use by subclasses. */
42 protected ForwardingIterator() {}
43
44 @Override
45 protected abstract Iterator<T> delegate();
46
47 @Override
48 public boolean hasNext() {
49 return delegate().hasNext();
50 }
51
52 @CanIgnoreReturnValue
53 @Override
54 public T next() {
55 return delegate().next();
56 }
57
58 @Override
59 public void remove() {
60 delegate().remove();
61 }
62 }