测试Map中的一些方法和遍历

public class TestMap {
    @Test
    public void   test7(){
        Map map = new HashMap<>();
        map.put("aa",123);
        map.put("bb",1234);
        map.put("cc",1245);
        //1. 此时输出的全是值  value
        System.out.println(map);
        //2. 遍历所有的Map中的Key；
        Set set = map.keySet();
        Iterator it = set.iterator();
        while(it.hasNext()){
            System.out.println(it.next());
        }
        //3. 用增强for循环遍历 map中所有的值
        Collection co = map.values();
        for(Object obj: co){
            System.out.println(obj);
        }
        //4  运用迭代器遍历 key和value。
        //方法一
         Set str = map.entrySet();
        Iterator ite = str.iterator();
        while(ite.hasNext()){
            System.out.println(ite.next());
        }
        //方法二
        Set str1 = map.entrySet();
        Iterator it1 = str1.iterator();
        while(it1.hasNext()){
            Object obj = it1.next();
            Map.Entry  s2 = (Map.Entry) obj;
            System.out.println(s2.getKey()+"......"+s2.getValue());
        }
            //方法3
        Set str2 = map.keySet();
        Iterator it2 =str2.iterator();
        while(it2.hasNext()){
            Object obj = it2.next();

            Object value = map.get(obj);
            System.out.println(obj+","+value);
        }
    }
}