迭代器模式

package Iterator_pattern;

import java.util.ArrayList;

public interface Aggregate {
	 int getlength();
	 Object getvalue(int index);
	public Iterator creiterotor();
}

package Iterator_pattern;

import java.util.ArrayList;

public interface Iterator {
	public boolean isnext( );
	public Object next();
}

package Iterator_pattern;

import java.util.ArrayList;
import java.util.Iterator;

public class ConcreteAggregate implements Aggregate{

	public  ArrayList<String> list;
	public ConcreteAggregate(ArrayList<String> list) {
	 
		this.list = list;
	}
	 
	 void add(String s){
		 list.add(s);
	 }

	@Override
	public Iterator_pattern.Iterator creiterotor() {
		// TODO Auto-generated method stub
		return  new ConcreteIterator(this);
	}

	@Override
	public int getlength() {
		// TODO Auto-generated method stub
		return list.size();
	}

	@Override
	public Object getvalue(int index) {
		// TODO Auto-generated method stub
		return list .get(index);
	}
}

package Iterator_pattern;

import java.util.ArrayList;

public class ConcreteIterator implements Iterator{
	
	private Aggregate ag;
	public ConcreteIterator(Aggregate ag){
		this.ag = ag;
	}
	private static int  Currindex = 1;
	@Override
	public boolean isnext() {
		// TODO Auto-generated method stub
		if(Currindex<ag.getlength()){
			
			return true;
		}
		return false;
	}

	@Override
	public Object next() {
		// TODO Auto-generated method stub
		if(isnext()){
			return ag.getvalue(Currindex++);
		}
		else
		return null;
	}

 

}

package Iterator_pattern;

import java.util.ArrayList;

public class App {
	public static void main(String args[]){
		ConcreteAggregate ca = new ConcreteAggregate(new ArrayList<String>());
		ca.list.add("a");
		ca.list.add("b");
		ca.list.add("c");
		ca.list.add("d");
		ca.list.add("e");
		ca.list.add("f");
		Iterator it = ca.creiterotor();
		System.out.println(it.isnext());
		System.out.println(it.next());
		System.out.println(it.next());
		System.out.println(it.next());
		System.out.println(it.next());
		System.out.println(it.next());
		System.out.println(it.next());
	 
}
}