1 /* 2 * Copyright (c) 2015, 2016, 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 26 package com.sun.tools.javac.util; 27 28 import java.util.Iterator; 29 import java.util.NoSuchElementException; 30 import java.util.function.Function; 31 import java.util.function.Predicate; 32 33 /** Utilities for Iterators. 34 * 35 * <p><b>This is NOT part of any supported API. 36 * If you write code that depends on this, you do so at your own risk. 37 * This code and its internal interfaces are subject to change or 38 * deletion without notice.</b> 39 */ 40 public class Iterators { 41 createCompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor)42 public static <I, O> Iterator<O> createCompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) { 43 return new CompoundIterator<>(inputs, convertor); 44 } 45 46 private static class CompoundIterator<I, O> implements Iterator<O> { 47 48 private final Iterator<I> inputs; 49 private final Function<I, Iterator<O>> convertor; 50 @SuppressWarnings("unchecked") 51 private Iterator<O> currentIterator = EMPTY; 52 CompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor)53 public CompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) { 54 this.inputs = inputs.iterator(); 55 this.convertor = convertor; 56 } 57 hasNext()58 public boolean hasNext() { 59 if (currentIterator != null && !currentIterator.hasNext()) { 60 update(); 61 } 62 return currentIterator != null; 63 } 64 next()65 public O next() { 66 if (currentIterator == EMPTY && !hasNext()) { 67 throw new NoSuchElementException(); 68 } 69 return currentIterator.next(); 70 } 71 remove()72 public void remove() { 73 throw new UnsupportedOperationException(); 74 } 75 update()76 private void update() { 77 while (inputs.hasNext()) { 78 currentIterator = convertor.apply(inputs.next()); 79 if (currentIterator.hasNext()) return; 80 } 81 currentIterator = null; 82 } 83 } 84 85 @SuppressWarnings("rawtypes") 86 private final static Iterator EMPTY = new Iterator() { 87 public boolean hasNext() { 88 return false; 89 } 90 91 @Override 92 public Object next() { 93 return null; 94 } 95 }; 96 createFilterIterator(Iterator<E> input, Predicate<E> test)97 public static <E> Iterator<E> createFilterIterator(Iterator<E> input, Predicate<E> test) { 98 return new Iterator<E>() { 99 private E current = update(); 100 private E update () { 101 while (input.hasNext()) { 102 E sym = input.next(); 103 if (test.test(sym)) { 104 return sym; 105 } 106 } 107 108 return null; 109 } 110 @Override 111 public boolean hasNext() { 112 return current != null; 113 } 114 115 @Override 116 public E next() { 117 E res = current; 118 current = update(); 119 return res; 120 } 121 }; 122 } 123 124 } 125