如何在android中将Json对象附加到已有json文件中

import org.json.JSONException;
import org.json.JSONObject;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 1. 读取已有的JSON文件
        File jsonFile = new File(getFilesDir(), "data.json");
        String existingJsonString = readJsonFile(jsonFile);

        try {
            // 2. 解析已有的JSON文件
            JSONObject existingJsonObj = new JSONObject(existingJsonString);

            // 3. 创建要附加的JSON对象
            JSONObject newJsonObj = new JSONObject();
            newJsonObj.put("key", "value");

            // 4. 将要附加的JSON对象合并到已有的JSON对象中
            existingJsonObj.put("newData", newJsonObj);

            // 5. 将合并后的JSON对象转换为字符串
            String mergedJsonString = existingJsonObj.toString();

            // 6. 将字符串写入文件
            writeJsonFile(jsonFile, mergedJsonString);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    private String readJsonFile(File file) {
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(file);
            byte[] buffer = new byte[fis.available()];
            fis.read(buffer);
            return new String(buffer);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }

    private void writeJsonFile(File file, String jsonString) {
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(file);
            fos.write(jsonString.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}