设计模式16：迭代器模式

泛型相关请参考：http://www.cnblogs.com/lwbqqyumidi/p/3837629.html

uml：

Aggregate及其子类：

public abstract class Aggregate<T> {
	
	public abstract Iterator<T> getIterator();
	public abstract T get(int index);
	public abstract int getLength();
	public abstract void add(T e);
	public abstract void remove(T e);

}

import java.util.ArrayList;
import java.util.List;

public class ConcreteAggregate<T> extends Aggregate<T> {
	
	private List<T> list = new ArrayList<>();
	
	@Override
	public int getLength(){
		return list.size();
	}
	
	@Override
	public void add(T item) {
		list.add(item);
	}
	
	@Override
	public void remove(T item) {
		list.remove(item);
	}
	
	@Override
	public T get(int index){
		return list.get(index);
	}

	@Override
	public Iterator<T> getIterator() {
		return new ConcreteIterator<T>(this);
	}

}

　　

Iterator及其子类：

public abstract class Iterator<T> {
	
	public abstract boolean hasNext();
	public abstract T next();
}

public class ConcreteIterator<T> extends Iterator<T> {
	
	private ConcreteAggregate<T> aggr;
	private int current = 0;
	
	public ConcreteIterator(ConcreteAggregate<T> aggr) {
		this.aggr = aggr;
	}

	@Override
	public boolean hasNext() {
		return current < aggr.getLength() ? true : false;
	}

	@Override
	public T next() {
		// TODO Auto-generated method stub
		current++;
		return aggr.get(current - 1);
	}

}

Demo：

public class IteratorDemo {
	
	public static void main(String[] args) {
		Aggregate<Integer> aggregate = new ConcreteAggregate<>();
		for(int i = 0; i < 10; i++){
			aggregate.add(i);
		}
		Iterator<Integer> iterator = aggregate.getIterator();
		while(iterator.hasNext()){
			System.out.println(iterator.next());
		}
	}

}