java json与对象或者集合互转

package open_exe;

public class User {

    private int id;
    private String name;
    private String gender;

    public User() {

    }

    public User(int id, String name, String gender) {
        this.id = id;
        this.name = name;
        this.gender = gender;
    }

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
}

package open_exe;

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

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

public class Jsonzhuanhuan{
    static String objectToJsonString(){
        JSONObject jsonObject = JSONObject.fromObject(new User(1, "张三", "男"));//java对象转json对象
        return jsonObject.toString();
    }

    static void jsonStringToObject(String jsonString){
        JSONObject jsonObject = JSONObject.fromObject(jsonString);
        User user = (User)JSONObject.toBean(jsonObject, User.class);//json对象转java对象需要注意 json对象属性名称首字母为大写会出错
        System.out.println(user.getName());
    }

    /**
     * 将Java集合转换为Json字符串
     *
     *
     */
    static String collectionToJsonString(){
        List<User> userList = new ArrayList<User>();
        userList.add(new User(1, "张三", "男"));
        userList.add(new User(2, "李四", "女"));
        userList.add(new User(3, "王五", "男"));
        JSONArray jsonArray = JSONArray.fromObject(userList);
        return jsonArray.toString();
        String[] arr = {"asd","dfgd","asd","234"};//补充内容  数组转json

JSONArray jsonarray = JSONArray.fromObject(arr);

    }

    /**
     * 将Json字符串转换为Java集合
     *
     *
     */
    static void jsonStringToCollection(String jsonString){
        JSONArray jsonArray = JSONArray.fromObject(jsonString);
        @SuppressWarnings("unchecked")
        List<User> userList = (List<User>)JSONArray.toCollection(jsonArray, User.class);
        for (User user : userList) {
            System.out.println(user.getName());
        }
    }
    public static void main(String[] args) {
        System.out.println(objectToJsonString());//对象转json
        jsonStringToObject(objectToJsonString());//json转对象

        System.out.println(collectionToJsonString());
        jsonStringToCollection(collectionToJsonString());
    }
}