| /* |
| * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package com.sun.tools.javac.util; |
| |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| import java.util.function.Function; |
| import java.util.function.Predicate; |
| |
| /** Utilities for Iterators. |
| * |
| * <p><b>This is NOT part of any supported API. |
| * If you write code that depends on this, you do so at your own risk. |
| * This code and its internal interfaces are subject to change or |
| * deletion without notice.</b> |
| */ |
| public class Iterators { |
| |
| public static <I, O> Iterator<O> createCompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) { |
| return new CompoundIterator<>(inputs, convertor); |
| } |
| |
| private static class CompoundIterator<I, O> implements Iterator<O> { |
| |
| private final Iterator<I> inputs; |
| private final Function<I, Iterator<O>> convertor; |
| @SuppressWarnings("unchecked") |
| private Iterator<O> currentIterator = EMPTY; |
| |
| public CompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) { |
| this.inputs = inputs.iterator(); |
| this.convertor = convertor; |
| } |
| |
| public boolean hasNext() { |
| if (currentIterator != null && !currentIterator.hasNext()) { |
| update(); |
| } |
| return currentIterator != null; |
| } |
| |
| public O next() { |
| if (currentIterator == EMPTY && !hasNext()) { |
| throw new NoSuchElementException(); |
| } |
| return currentIterator.next(); |
| } |
| |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| private void update() { |
| while (inputs.hasNext()) { |
| currentIterator = convertor.apply(inputs.next()); |
| if (currentIterator.hasNext()) return; |
| } |
| currentIterator = null; |
| } |
| } |
| |
| @SuppressWarnings("rawtypes") |
| private final static Iterator EMPTY = new Iterator() { |
| public boolean hasNext() { |
| return false; |
| } |
| |
| @Override |
| public Object next() { |
| return null; |
| } |
| }; |
| |
| public static <E> Iterator<E> createFilterIterator(Iterator<E> input, Predicate<E> test) { |
| return new Iterator<E>() { |
| private E current = update(); |
| private E update () { |
| while (input.hasNext()) { |
| E sym = input.next(); |
| if (test.test(sym)) { |
| return sym; |
| } |
| } |
| |
| return null; |
| } |
| @Override |
| public boolean hasNext() { |
| return current != null; |
| } |
| |
| @Override |
| public E next() { |
| E res = current; |
| current = update(); |
| return res; |
| } |
| }; |
| } |
| |
| } |