How do you set a key in a JSONObject in Java?

In Java, you can use the `put()` method to set key-value pairs in a JSON object. Here is an example:

import org.json.JSONObject;
public class Main {
    public static void main(String[] args) {
        // 创建一个空的JSON对象
        JSONObject jsonObject = new JSONObject();
        // 设置键值对
        jsonObject.put("key1", "value1");
        jsonObject.put("key2", "value2");
        // 打印JSON对象
        System.out.println(jsonObject);
    }
}

Running the above code will produce the following results:

{"key1":"value1","key2":"value2"}

In this example, we are using the `put()` method to set key-value pairs. The first parameter is the key and the second parameter is the value.