需要的jar包：json-lib-2.4-jdk15.jar

package com.xxx.xxx.json;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class JsonMain {

	public static void main(String[] args) {
		////////////////////////////////////////
		/**
		 * 对于【数组】和【list集合】使用JSONArray.fromObject("#########");
		 * 
		 * 对于【map集合】 和 【对象 】使用JSONObject.fromObject("#########");
		 */
		////////////////////////////////////////
		// java数组转json int数组
		int[] arr = { 4, 8, 6, 4, 8, 7 };
		JSONArray jsonArr = JSONArray.fromObject(arr);
		System.out.println(jsonArr);//////////[4,8,6,4,8,7]
		
		// java数组转json String数组
		String[] arrStr = { "qq", "ww", "ee", "rr" };
		JSONArray jsonArrStr = JSONArray.fromObject(arrStr);
		System.out.println(jsonArrStr);/////////["qq","ww","ee","rr"]
		
		// list集合转json list集合
		ArrayList<String> list = new ArrayList<>();
		list.add("aa");
		list.add("bb");
		list.add("cc");
		JSONArray jsonList = JSONArray.fromObject(list);
		System.out.println(jsonList);///////////["aa","bb","cc"]
		
		// list 集合 <User>
		ArrayList<User> userList = new ArrayList<>();
		userList.add(new User("站三", 18));
		userList.add(new User("李四", 34));
		userList.add(new User("王五", 24));
		JSONArray listArrList = JSONArray.fromObject(userList);
		System.out.println(listArrList);
		//////////[{"age":18,"name":"站三"},{"age":34,"name":"李四"},{"age":24,"name":"王五"}]
		//////////////////////////////////////////////////////
		// map转json <String, String>
		HashMap<String, String> map = new HashMap<>();
		map.put("aa", "a11");
		map.put("bb", "b11");
		map.put("cc", "c11");
		JSONObject jsonMap = JSONObject.fromObject(map);
		System.out.println(jsonMap);/////////{"aa":"a11","bb":"b11","cc":"c11"}
		
		// map转json <String, Integer>
		HashMap<String, Integer> map1 = new HashMap<>();
		map1.put("aa", 111);
		map1.put("bb", 222);
		map1.put("cc", 333);
		JSONObject jsonMap1 = JSONObject.fromObject(map1);
		System.out.println(jsonMap1);////////////{"aa":111,"bb":222,"cc":333}
		
		// 对象转json User
		User user1 = new User("站三", 18);
		JSONObject user1Json = JSONObject.fromObject(user1);
		System.out.println(user1Json);///////////{"age":18,"name":"站三"}
		
		User user2 = new User("李四", 18);
		JSONObject user2Json = JSONObject.fromObject(user2);
		System.out.println(user2Json);//////////{"age":18,"name":"李四"}
	}

}