001/* 002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved. 003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 004 * 005 * Project and contact information: http://www.cascading.org/ 006 * 007 * This file is part of the Cascading project. 008 * 009 * Licensed under the Apache License, Version 2.0 (the "License"); 010 * you may not use this file except in compliance with the License. 011 * You may obtain a copy of the License at 012 * 013 * http://www.apache.org/licenses/LICENSE-2.0 014 * 015 * Unless required by applicable law or agreed to in writing, software 016 * distributed under the License is distributed on an "AS IS" BASIS, 017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 018 * See the License for the specific language governing permissions and 019 * limitations under the License. 020 */ 021 022package cascading.tuple; 023 024import java.io.Closeable; 025import java.io.IOException; 026import java.util.Iterator; 027 028import cascading.tuple.util.Resettable; 029 030/** 031 * TupleChainIterator chains the given Iterators into a single Iterator. 032 * <p> 033 * As one iterator is completed, it will be closed and a new one will start. 034 */ 035public class TupleChainIterator implements Iterator<Tuple>, Closeable, Resettable<Iterator<Tuple>> 036 { 037 /** Field iterator */ 038 Iterator<Tuple>[] iterators; 039 int currentIterator = 0; 040 041 public TupleChainIterator( Iterator<Tuple>... iterators ) 042 { 043 this.iterators = iterators; 044 } 045 046 /** 047 * Method hasNext returns true if there is a next TupleEntry 048 * 049 * @return boolean 050 */ 051 public boolean hasNext() 052 { 053 if( iterators.length < currentIterator + 1 ) // past the end 054 return false; 055 056 if( iterators[ currentIterator ].hasNext() ) 057 return true; 058 059 closeCurrent(); 060 061 currentIterator++; 062 063 return iterators.length != currentIterator && hasNext(); 064 } 065 066 @Override 067 public void reset( Iterator<Tuple>... iterators ) 068 { 069 this.currentIterator = 0; 070 this.iterators = iterators; 071 } 072 073 /** 074 * Method next returns the next TupleEntry. 075 * 076 * @return TupleEntry 077 */ 078 public Tuple next() 079 { 080 hasNext(); // force roll to next iterator 081 082 return iterators[ currentIterator ].next(); 083 } 084 085 /** Method remove removes the current Tuple from the underlying collection. */ 086 public void remove() 087 { 088 iterators[ currentIterator ].remove(); 089 } 090 091 /** Method close closes all underlying resources. */ 092 @Override 093 public void close() 094 { 095 if( iterators.length != currentIterator ) 096 closeCurrent(); 097 } 098 099 protected void closeCurrent() 100 { 101 close( iterators[ currentIterator ] ); 102 } 103 104 private void close( Iterator iterator ) 105 { 106 if( iterator instanceof Closeable ) 107 { 108 try 109 { 110 ( (Closeable) iterator ).close(); 111 } 112 catch( IOException exception ) 113 { 114 // ignore 115 } 116 } 117 } 118 }