1 /* 2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package com.sun.tools.javac.util; 26 27 import java.util.Iterator; 28 import java.util.NoSuchElementException; 29 import java.util.function.Function; 30 31 public class Iterators { 32 33 public static <I, O> Iterator<O> createCompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) { 34 return new CompoundIterator<>(inputs, convertor); 35 } 36 37 private static class CompoundIterator<I, O> implements Iterator<O> { 38 39 private final Iterator<I> inputs; 40 private final Function<I, Iterator<O>> convertor; 41 private Iterator<O> currentIterator; 42 43 public CompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) { 44 this.inputs = inputs.iterator(); 45 this.convertor = convertor; 46 } 47 48 public boolean hasNext() { 49 while (inputs.hasNext() && (currentIterator == null || !currentIterator.hasNext())) { 50 currentIterator = convertor.apply(inputs.next()); 51 } 52 return currentIterator != null && currentIterator.hasNext(); 53 } 54 55 public O next() { 56 if (!hasNext()) 57 throw new NoSuchElementException(); 58 59 return currentIterator.next(); 60 } 61 62 public void remove() { 63 throw new UnsupportedOperationException(); 64 } 65 } 66 }