1 /* 2 * Copyright (C) 2020 The Android Open Source Project 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.android.timezone.location.storage.tzs2range.write; 18 19 import java.util.ArrayList; 20 import java.util.Iterator; 21 22 /** 23 * An iterator that can have elements pushed back onto it. {@link #remove()} is not supported. 24 * 25 * @param <E> The type of the element returned by this iterator 26 */ 27 public final class PushBackIterator<E> implements Iterator<E> { 28 29 private final ArrayList<E> mPushBackStack = new ArrayList<>(); 30 31 private final Iterator<E> mIterator; 32 PushBackIterator(Iterator<E> iterator)33 public PushBackIterator(Iterator<E> iterator) { 34 mIterator = iterator; 35 } 36 37 @Override hasNext()38 public boolean hasNext() { 39 return !mPushBackStack.isEmpty() || mIterator.hasNext(); 40 } 41 42 @Override next()43 public E next() { 44 if (!mPushBackStack.isEmpty()) { 45 return mPushBackStack.remove(mPushBackStack.size() - 1); 46 } 47 return mIterator.next(); 48 } 49 50 /** 51 * Pushes the element to the front of the iterator again. 52 */ pushBack(E element)53 public void pushBack(E element) { 54 mPushBackStack.add(element); 55 } 56 } 57