001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.geometry.core.internal; 018 019import java.util.Collection; 020import java.util.Deque; 021import java.util.Iterator; 022import java.util.LinkedList; 023import java.util.NoSuchElementException; 024 025/** Class that wraps another iterator, converting each input iterator value into 026 * one or more output iterator values. 027 * @param <I> Input iterator type 028 * @param <T> Output iterator type 029 */ 030public abstract class IteratorTransform<I, T> implements Iterator<T> { 031 032 /** Input iterator instance that supplies the input values for this instance. */ 033 private final Iterator<I> inputIterator; 034 035 /** Output value queue. */ 036 private final Deque<T> outputQueue = new LinkedList<>(); 037 038 /** Create a new instance that uses the given iterator as the input source. 039 * @param inputIterator iterator supplying input values 040 */ 041 protected IteratorTransform(final Iterator<I> inputIterator) { 042 this.inputIterator = inputIterator; 043 } 044 045 /** {@inheritDoc} */ 046 @Override 047 public boolean hasNext() { 048 return loadNextOutput(); 049 } 050 051 /** {@inheritDoc} */ 052 @Override 053 public T next() { 054 if (outputQueue.isEmpty()) { 055 throw new NoSuchElementException(); 056 } 057 058 return outputQueue.removeFirst(); 059 } 060 061 /** Load the next output values into the output queue. Returns true if the output queue 062 * contains more entries. 063 * @return true if more output values are available 064 */ 065 private boolean loadNextOutput() { 066 while (outputQueue.isEmpty() && inputIterator.hasNext()) { 067 acceptInput(inputIterator.next()); 068 } 069 070 return !outputQueue.isEmpty(); 071 } 072 073 /** Add a value to the output queue. 074 * @param value value to add to the output queue 075 */ 076 protected void addOutput(final T value) { 077 outputQueue.add(value); 078 } 079 080 /** Add multiple values to the output queue. 081 * @param values values to add to the output queue 082 */ 083 protected void addAllOutput(final Collection<T> values) { 084 outputQueue.addAll(values); 085 } 086 087 /** Accept a value from the input iterator. This method should take 088 * the input value and add one or more values to the output queue. 089 * @param input value from the input iterator 090 */ 091 protected abstract void acceptInput(I input); 092}