001// *************************************************************************************************************************** 002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file * 003// * distributed with this work for additional information regarding copyright ownership. The ASF licenses this file * 004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance * 005// * with the License. You may obtain a copy of the License at * 006// * * 007// * http://www.apache.org/licenses/LICENSE-2.0 * 008// * * 009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an * 010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the * 011// * specific language governing permissions and limitations under the License. * 012// *************************************************************************************************************************** 013package org.apache.juneau.internal; 014 015import static org.apache.juneau.internal.ThrowableUtils.*; 016 017import java.util.*; 018 019/** 020 * Utility class for defining an iterator over one or more iterables. 021 * 022 * @param <E> The element class type. 023 */ 024public class MultiIterable<E> implements Iterable<E> { 025 026 final List<Iterator<E>> iterators = new LinkedList<>(); 027 028 /** 029 * Constructor. 030 * 031 * @param iterators The list of iterators to iterate over. 032 */ 033 @SuppressWarnings("unchecked") 034 public MultiIterable(Iterator<E>...iterators) { 035 for (Iterator<E> i : iterators) 036 append(i); 037 } 038 039 /** 040 * Appends the specified iterator to this list of iterators. 041 * 042 * @param iterator The iterator to append. 043 * @return This object (for method chaining). 044 */ 045 public MultiIterable<E> append(Iterator<E> iterator) { 046 assertFieldNotNull(iterator, "iterator"); 047 this.iterators.add(iterator); 048 return this; 049 } 050 051 @Override /* Iterable */ 052 public Iterator<E> iterator() { 053 return new Iterator<E>() { 054 Iterator<Iterator<E>> i1 = iterators.iterator(); 055 Iterator<E> i2 = i1.hasNext() ? i1.next() : null; 056 057 @Override /* Iterator */ 058 public boolean hasNext() { 059 while (i2 != null && ! i2.hasNext()) 060 i2 = (i1.hasNext() ? i1.next() : null); 061 return (i2 != null); 062 } 063 064 @Override /* Iterator */ 065 public E next() { 066 hasNext(); 067 if (i2 == null) 068 throw new NoSuchElementException(); 069 return i2.next(); 070 } 071 072 @Override /* Iterator */ 073 public void remove() { 074 if (i2 == null) 075 throw new NoSuchElementException(); 076 i2.remove(); 077 } 078 }; 079 } 080}