Java对象，Map，List，Set数组等相互转换大全（详细讲解,附代码，讲解案例）（二）

package com.example.面向对象1;
import java.util.*;
public class listdemo2 {
    public static void main(String[] args) {
        //  List转换为Array
        List<String> list1 = new ArrayList<>();
        list1.add("AAAA");
        list1.add("BBBB");
        list1.add("CCCC");
        list1.add("DDDD");
        String[] array = list1.toArray(new String[list1.size()]);
        for (String animal : array) {
            System.out.println(animal);
        }
        //Array转换为List
        String[] countries = {"AAAA", "BBBB", "CCCC", "DDDD"};
        List list2 = Arrays.asList(countries);
        System.out.println(list2);
    }
}

package com.example.democrud.democurd.controller;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class indexof {
    public static void main(String[] args) {
        //  List转换为JSONArray
        List<String> list1 = new ArrayList<>();
        list1.add("AAAA");
        list1.add("BBBB");
        list1.add("CCCC");
        list1.add("DDDD");
        String[] array = list1.toArray(new String[list1.size()]);
        for (String animal : array) {
            System.out.println(animal);
        }
        System.out.println("List转换为JSONArray");
        JSONArray array1= JSONArray.parseArray(JSON.toJSONString(list1));
        System.out.println("List转换为JSONArray"+array1);
        System.out.println("---------------------------------");
        //创建一个对象
        User user1 = new User("秦疆1号", 3, "男");
        User user2 = new User("秦疆2号", 3, "男");
        User user3 = new User("秦疆3号", 3, "男");
        User user4 = new User("秦疆4号", 3, "男");
        List<User> list = new ArrayList<User>();
        list.add(user1);
        list.add(user2);
        list.add(user3);
        list.add(user4);
            System.out.println(list);
        System.out.println("List转换为JSONArray");
        JSONArray array3= JSONArray.parseArray(JSON.toJSONString(list));
        System.out.println("List转JSONArray"+array3);
        System.out.println("---------------------------------");
        List<User> list2 = JSONObject.parseArray(array3.toJSONString(), User.class);
        System.out.println("JSONArray转List"+list2);
    }
}

AAAA
BBBB
CCCC
DDDD
List转换为JSONArray
List转换为JSONArray["AAAA","BBBB","CCCC","DDDD"]
---------------------------------
[User(name=秦疆1号, age=3, sex=男), User(name=秦疆2号, age=3, sex=男), User(name=秦疆3号, age=3, sex=男), User(name=秦疆4号, age=3, sex=男)]
List转换为JSONArray
List转JSONArray[{"sex":"男","name":"秦疆1号","age":3},{"sex":"男","name":"秦疆2号","age":3},{"sex":"男","name":"秦疆3号","age":3},{"sex":"男","name":"秦疆4号","age":3}]
---------------------------------
JSONArray转List[User(name=秦疆1号, age=3, sex=男), User(name=秦疆2号, age=3, sex=男), User(name=秦疆3号, age=3, sex=男), User(name=秦疆4号, age=3, sex=男)]

package com.example.demo.controller.Demo;
import com.example.demo.entity.User;
import org.apache.commons.beanutils.BeanUtils;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class demoTest3 {
    public static void main(String[] args) {
        //  Map的Key值转换为List
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "AAAA");
        map.put(2, "BBBB");
        map.put(3, "CCCC");
        map.put(4, "DDDD");
        List<Integer> list = new ArrayList<Integer>(map.keySet());
        System.out.println("\n******  Map的Key值转换为List ******");
        System.out.println("map.keySet()==>" + list);
        //  Map的Value值转换为List
        Map<Integer, String> map1 = new HashMap<>();
        map1.put(1, "AAAA");
        map1.put(2, "BBBB");
        map1.put(3, "CCCC");
        map1.put(4, "DDDD");
        List<String> list1 = new ArrayList<String>(map.values());
        System.out.println("\n******  Map的Value值转换为List ******");
        System.out.println("map.values()==>" + list1);
    }
}

package com.example.demo.controller.Demo;
import com.example.demo.entity.User;
import org.apache.commons.beanutils.BeanUtils;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.*;
public class demoTest3 {
    public static void main(String[] args) {
        //  Map的Key值转换为List
        Map<Integer,String> map = new HashMap<>();
        map.put(1,"AAAA");
        map.put(2,"BBBB");
        map.put(3,"CCCC");
        map.put(4,"DDDD");
        Set<Integer> set = new HashSet<>(map.keySet());
        System.out.println("\n******  Map的Key值转换为Set ******");
        System.out.println("map.keySet()==>" + set);
       // Map的Value值转换为Set
        Map<Integer,String> map1 = new HashMap<>();
        map1.put(1,"AAAA");
        map1.put(2,"BBBB");
        map1.put(3,"CCCC");
        map1.put(4,"DDDD");
        Set<String> set1 = new HashSet<String>(map.values());
        System.out.println("\n******  Map的Value值转换为Set ******");
        System.out.println("map.values()==>" + set1);
    }
}