001 /*
002 * www.ti.bfh.ch
003 *
004 * Copyright 2007, Berne University of Applied Sciences,
005 * School of Engineering and Information Technology
006 * and individual contributors as indicated by the @authors tag.
007 *
008 * This is free software; you can redistribute it and/or modify it under the terms of the
009 * GNU Lesser General Public License as published by the Free Software Foundation;
010 * either version 3 of the License, or (at your option) any later version.
011 *
012 * This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
013 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
014 * See the GNU Lesser General Public License for more details.
015 *
016 * You should have received a copy of the GNU Lesser General Public License along with this software;
017 * if not, see <http://www.gnu.org/licenses/>.
018 *
019 */
020 package ch.bfh.algo.core.sequence;
021
022
023 import java.util.NoSuchElementException;
024
025 import ch.bfh.algo.InvalidAccessorException;
026
027
028
029 public class LinkedIterator<E,P extends GenericLinkedPosition<E,P>>{
030
031 private final GenericLinkedSequence<E,P> sequence;
032 private final LinkedCursor<E,P> cursor;
033 private P cache=null;
034
035 public LinkedIterator(GenericLinkedSequence<E,P> sequence, P before, P after){
036 this.sequence=sequence;
037 this.cursor=new LinkedCursor<E,P>(before,after);
038 }
039
040 public boolean hasNext(){
041 return this.cursor.getNext()!=this.sequence.tail();
042 }
043
044 public boolean hasPrevious(){
045 return this.cursor.getPrevious()!=this.sequence.head();
046 }
047
048 public P nextPosition(){
049 if(!this.hasNext()) throw new NoSuchElementException();
050 this.cache=this.cursor.getNext();
051 this.cursor.moveNext();
052 return this.cache;
053 }
054
055 public E nextElement(){
056 return this.nextPosition().element();
057 }
058
059 public int nextIndex(){
060 if(!this.hasNext()) return this.sequence.size();
061 return this.sequence.rank(this.cursor.getNext());
062 }
063
064 public P previousPosition(){
065 if(!this.hasPrevious()) throw new NoSuchElementException();
066 this.cache=this.cursor.getPrevious();
067 this.cursor.movePrevious();
068 return this.cache;
069 }
070
071 public E previousElement(){
072 return this.previousPosition().element();
073 }
074
075 public int previousIndex(){
076 if(!this.hasPrevious()) return -1;
077 return this.sequence.rank(this.cursor.getPrevious());
078 }
079
080 private void setIllegalState(){
081 this.cache=null;
082 }
083
084 private boolean isIllegalSate(){
085 return this.cache==null;
086 }
087
088 public void addElement(E element){
089 this.sequence.insertBetween(this.cursor.getPrevious(),this.cursor.getNext(),element);
090 this.setIllegalState();
091 }
092
093 public void remove(){
094 if(this.isIllegalSate()) throw new IllegalStateException();
095 try{
096 this.sequence.delete(this.cache);
097 }catch(InvalidAccessorException e){
098 throw new IllegalStateException();
099 }
100 finally{this.setIllegalState();}
101 }
102
103 public void setElement(E element){
104 if(this.isIllegalSate()) throw new IllegalStateException();
105 try{
106 this.sequence.replace(this.cache,element);
107 }catch(InvalidAccessorException e){
108 this.setIllegalState();
109 throw new IllegalStateException();
110 }
111 }
112
113 public void finalize() throws Throwable{
114 synchronized(this.sequence){
115 this.cursor.detach();
116 }
117 super.finalize();
118 }
119
120 }