20190219list map练习

list

Student s1=new Student("张三",1);
		Student s2=new Student("李四",2);
		Student s3=new Student("王五",2);

		List<Student> list=new ArrayList<Student>();
		list.add(s1);
		list.add(s2);
		list.add(s3);


	for(int i=0;i<list.size();i++)
	{
		System.out.println(list.get(i).getName());

	}

map  遍历注意Entry()

HashMap<Integer,String> map=new HashMap();
		map.put(1, "aaa");
		map.put(2, "bbb");
		map.put(3, "ccc");
		//map.remove(3);
//		for(Map.Entry<Integer, String> entry : map.entrySet())//遍历反法1
//		{
//			System.out.println(entry.getKey()+entry.getValue());
//		}
		//遍历方法2
		for(Integer key :map.keySet())
		{
			System.out.println(key);
		}

		for(String val :map.values())
		{
			System.out.println(val);
		}
		//遍历方法3
		Iterator<Map.Entry<Integer, String>> it=map.entrySet().iterator();
		while(it.hasNext())
		{
			Map.Entry<Integer, String> ma=it.next();
			System.out.println(ma.getKey());
			System.out.println(ma.getValue());
		}
	}