2021-09-30

public void test02(){
        Map map1 = new HashMap();
        map1.put("AA",34);
        map1.put("DD",310);
        map1.put("NN",68);
        map1.put("WE",54);
        map1.put("AA",200);

        System.out.println(map1);
        Set set = map1.keySet();

        //1使用迭代器遍历集合中的键
        Iterator iterator = set.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next());
        }
        //2使用foreach遍历集合中的键
        for(Object obj : set){
            System.out.println(obj);
        }

        //使用迭代器进行遍历值
        Collection collection = map1.values();
        Iterator iterator1 = collection.iterator();
        while (iterator1.hasNext()){
            System.out.println(iterator1.next());
        }

        //使用foreach循环遍历集合中的元素
        for(Object obj2 : collection){
            System.out.println(obj2);
        }

        //使用迭代器遍历键值对
        Set set1 = map1.entrySet();
        Iterator iterator2 = set1.iterator();
        while(iterator2.hasNext()){
            System.out.println(iterator2.next());
        }

        //使用foreach遍历map的键值对
        for(Object obj3 : set1){
            System.out.println(obj3);
        }

        //分别获取键和值
        Iterator iterator3 = set1.iterator();
        while(iterator3.hasNext()){
            Object obj = iterator3.next();
            Map.Entry entry = (Map.Entry) obj;
            System.out.println(entry.getKey()+"------->"+entry.getValue());
        }


    }