JsonObject、Map、Set、ArrayList、List的操作(java)

        只要是会点代码的，面试总逃不开map、arraylist这些，直接贴代码吧

JsonObject

        JSONObject json = new JSONObject();
        json.put("username","alice");
        json.put("password","1234");
        json.put("age",15);
        System.out.println(json);
        Set keyset= json.keySet();
        Iterator iterator = keyset.iterator();
        while(iterator.hasNext()){
           String key = iterator.next();
           String value = json.getString(key);
           System.out.println(key+":"+value);
        }

运行结果：

{"password":"1234","age":15,"username":"alice"}
password:1234
age:15
username:alice

Set

        Set set = new HashSet();
        set.add("aaa");
        set.add("bbb");
        set.add("ccc");
        System.out.println(set);
        set.remove("aaa");
        for(String str:set){
            System.out.println(str);
        }

运行结果：

[aaa, ccc, bbb]
ccc
bbb

Map

        Map map = new HashMap();
        map.put("username","alice");
        map.put("password","1234");
        map.put("age",15);
        System.out.println(map);
        Set keySet= json.keySet();
       for(String mapkey:keySet){
            String mapvalue = json.getString(mapkey);
            System.out.println(mapkey+":"+mapvalue);
        }

运行结果：

{password=1234, age=15, username=alice}
password:1234
username:alice

ArrayList

public static void main(String[] args) {
        ArrayList arrayList = new ArrayList();
        arrayList.add("a");
        arrayList.add("b");
        arrayList.add("c");
        arrayList.add("d");
        System.out.println(arrayList);
        arrayList.remove(1);
        System.out.println(arrayList);
        for(int i=0;i

打印结果：

[a, b, c, d]
[a, c, d]
a
c
d

List

        List list = new ArrayList();
        list.add("a");
        list.add("b");
        list.add("c");
        list.add("d");
        System.out.println(list);
        list.remove(1);
        System.out.println(list);
        for(int i=0;i 
运行结果：
 
 
 
[a, b, c, d]
 [a, c, d]
 a
 c
 d