How to parse 2D array returned from php to Java?

Question

I want to send a HTTP request to a php file where it will return a 2D array`. How can I send a 2D array and parse the array in Java?

request.php:

<?php
    $return_array = [["c1_r1", "c1_r2", "c1_r3"], ["c2_r1", "c2_r2", "c2_r3"], ["c3_r1", "c3_r2", "c3_r3"]];
    return $return_array;
?>

MainActivity.java:

package com.example.test;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.*;
import android.util.*;

import java.io.*;
import java.net.*;
import java.util.*;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        StrictMode.ThreadPolicy mypolicy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(mypolicy);

        try {
            URL url = new URL("http://XXX.XXX.X.XXX/request.php");
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestMethod("GET");
            BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream()));

            // HOW TO PARSE THE RETURNED 2D array HERE. JUST LIKE THE 2D array STORED IN THE `request.php`

            reader.close();
            con.disconnect();
        } catch (Exception e) {
            Log.e("console", "FAIL " + e);
        }
    }
}