利用迭代器，适配器模式实现统一数据访问接口。

package com.iterator;

public interface Iter {
	
	int next();
	boolean hasNext();

}

package com.iterator;

public class ArrayIter implements Iter {
	
	private int[] array;
	private int index;
	

	public ArrayIter(int[] array) {
		super();
		this.array = array;
		this.index=0;
	}

	@Override
	public int next() {
		// TODO Auto-generated method stub
		return array[index++];
	}

	@Override
	public boolean hasNext() {
		// TODO Auto-generated method stub
		return index<array.length;
	}

}


package com.iterator;

import java.util.List;

public class ListIter implements Iter {
	private List<Integer> list;
	private int index;

	public ListIter(List<Integer> list) {
		super();
		this.list = list;
		this.index = 0;
	}

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

	@Override
	public boolean hasNext() {
		// TODO Auto-generated method stub
		return index < list.size();
	}

}


package com.iterator;

public class ContextEnv {
	
	public int getSumList(Iter it){
		int sum=0;
		while(it.hasNext()){
			
			sum+=it.next();
		}
		return sum;
	}

}



package com.iterator;

import java.util.Arrays;
import java.util.List;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		ContextEnv lContextEnv = new ContextEnv();
		int[] arr = { 1, 2, 3, 5 };
		int sum1 = lContextEnv.getSumList(new ArrayIter(arr));
		System.err.println(sum1);
		//
		List<Integer> list = Arrays.asList(1, 2, 3, 5);
		int sum2 = lContextEnv.getSumList(new ListIter(list));
		System.err.println(sum2);
	}

}