Iterator pattern or Cursor
Iterator pattern provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
The iterator pattern decouples algorithms from containers; in some cases, algorithms are necessarily container-specific and thus cannot be decoupled.
package designpattern.iterator;
public interface Iterator {
public boolean hasNext();
public Object next();
}
public interface IContainer {
public Iterator getIterator();
}
public class Mp3Player implements IContainer {
private int size;
private int index;
private Object songsList[];
public Mp3Player(int size) {
songsList = new Object[size];
this.size = size;
index = 0;
}
@Override
public Iterator getIterator() {
return new SongsIterator();
}
private class SongsIterator implements Iterator {
int index;
@Override
public boolean hasNext() {
if(index<songsList.length) {
return true;
}
return false;
}
@Override
public Object next() {
if(this.hasNext()) {
return songsList[index++];
}
return null;
}
}
public void addName(Object string) {
if(index<size) {
songsList[index] = string;
}
index++;
}
}
public class IteratorPatternTest {
public static void main(String[] args) {
Mp3Player mp3Player = new Mp3Player(2);
mp3Player.addName("Is it love");
mp3Player.addName("Feel me");
Iterator iter = mp3Player.getIterator();
while(iter.hasNext()) {
String name = (String) iter.next();
System.out.println("Song : " + name);
}
}
}
Output:
Song : Is it love
Song : Feel me
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