迭代器模式

public interface A{
	public AIterator createIterator();
}

public interface AIterator{
	public Object next();
	public Object previous()
	public boolean hasNext();
}

public class AImpl implements A{
	public AIterator createIterator(){
		return new AIterator(this);
	}
}

public class AIteratorImpl implements AIterator{
	A a;
	int index;
	
	public AIterator(A a){
		this.a =a;
	}
	public Object next(){
		return a[index++]
	}
	public Object previous(){
		return a[index--]
	}
	public boolean hasNext(){
		return index == a.length;
	}
}