001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import com.google.common.annotations.GwtCompatible; 020import com.google.errorprone.annotations.CanIgnoreReturnValue; 021import java.util.Iterator; 022 023/** 024 * An iterator which forwards all its method calls to another iterator. Subclasses should override 025 * one or more methods to modify the behavior of the backing iterator as desired per the <a 026 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 027 * 028 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code 029 * default} methods. Specifically, it forwards calls only for methods that existed <a 030 * href="https://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html">before {@code default} 031 * methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it inherits their 032 * default implementations. When those implementations invoke methods, they invoke methods on the 033 * {@code ForwardingIterator}. 034 * 035 * @author Kevin Bourrillion 036 * @since 2.0 037 */ 038@GwtCompatible 039public abstract class ForwardingIterator<T> extends ForwardingObject implements Iterator<T> { 040 041 /** Constructor for use by subclasses. */ 042 protected ForwardingIterator() {} 043 044 @Override 045 protected abstract Iterator<T> delegate(); 046 047 @Override 048 public boolean hasNext() { 049 return delegate().hasNext(); 050 } 051 052 @CanIgnoreReturnValue 053 @Override 054 public T next() { 055 return delegate().next(); 056 } 057 058 @Override 059 public void remove() { 060 delegate().remove(); 061 } 062}