Map集合

HashMap<String,String> map=new HashMap<>();
        map.put("tom", "168");
        map.put("marry", "170");
        map.put("tob", "158");
        System.out.println(map.get("tom"));
        String a=map.put("blue", "168");
        String b=map.put("white", "170");
        String c=map.put("blue", "158");
        System.out.println(a);
        System.out.println(b);
        System.out.println(c);
//        获取
        System.out.println(map.get("tom"));
//        获取键值
        Set<Map.Entry<String,String>>  kv=map.entrySet();
        Iterator<Map.Entry<String,String>> iterator=kv.iterator();
        while(iterator.hasNext()) {
            System.out.println(iterator.next().getValue());
        }
//        获取键的集合
        Set<String> s=map.keySet();
        System.out.println(s);
        
        map.size();