利用java将json对转为json字符串

可以使用Java中的Gson库来将JSON对象转换成JSON字符串，示例如下：

import com.google.gson.Gson;

public class JsonExample {
    public static void main(String[] args) {
        // 创建JSON对象
        Person person = new Person("John", "Doe", 30);

        // 创建Gson对象
        Gson gson = new Gson();

        // 将JSON对象转换成JSON字符串
        String jsonString = gson.toJson(person);

        // 输出JSON字符串
        System.out.println(jsonString);
    }
}

class Person {
    private String firstName;
    private String lastName;
    private int age;

    public Person(String firstName, String lastName, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }
}

输出结果为：

{"firstName":"John","lastName":"Doe","age":30}