java泛型的使用

package com.wzh.test.generic;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.junit.Test;

public class Demo1 {

	@Test
	public void test1(){
		//List是接口，ArrayList是具体实现
		List<String> list=new ArrayList<String>();
		list.add("12");
		list.add("f");
		System.out.println(list);

		//传统迭代
		Iterator<String> it=list.iterator();
		while(it.hasNext()){
			String value=it.next();
			System.out.println(value);
		}

		//增强for
		for(String s : list){
			System.out.println(s);
		}
	}

	@Test
	public void test2(){
		//Map是接口，HashMap是具体实现
		//HashMap存入后无顺序，LinkedHashMap以存入顺序存储
		//Map<Integer,String> map=new HashMap<Integer,String>();
		Map<Integer,String> map=new LinkedHashMap<Integer, String>();
		map.put(3, "cc");
		map.put(2, "bb");
		map.put(1, "aa");

		//传统 keyset entryset
		Set<Map.Entry<Integer,String>> set=map.entrySet();
		Iterator<Map.Entry<Integer, String>> it=set.iterator();
		while(it.hasNext()){
			Map.Entry<Integer, String> entry=it.next();
			int key=entry.getKey();
			String value=entry.getValue();
			System.out.println(key+":"+value);
		}

		//增强for循环
		for(Map.Entry<Integer, String> m : map.entrySet()){
			int key=m.getKey();
			String value=m.getValue();
			System.out.println(key+":"+value);
		}

	}
}