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; 022import org.checkerframework.checker.nullness.qual.Nullable; 023 024/** 025 * An iterator which forwards all its method calls to another iterator. Subclasses should override 026 * one or more methods to modify the behavior of the backing iterator as desired per the <a 027 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 028 * 029 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code 030 * default} methods. Specifically, it forwards calls only for methods that existed <a 031 * href="https://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html">before {@code default} 032 * methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it inherits their 033 * default implementations. When those implementations invoke methods, they invoke methods on the 034 * {@code ForwardingIterator}. 035 * 036 * @author Kevin Bourrillion 037 * @since 2.0 038 */ 039@GwtCompatible 040@ElementTypesAreNonnullByDefault 041public abstract class ForwardingIterator<T extends @Nullable Object> extends ForwardingObject 042 implements Iterator<T> { 043 044 /** Constructor for use by subclasses. */ 045 protected ForwardingIterator() {} 046 047 @Override 048 protected abstract Iterator<T> delegate(); 049 050 @Override 051 public boolean hasNext() { 052 return delegate().hasNext(); 053 } 054 055 @CanIgnoreReturnValue 056 @Override 057 @ParametricNullness 058 public T next() { 059 return delegate().next(); 060 } 061 062 @Override 063 public void remove() { 064 delegate().remove(); 065 } 066}