Custom checker in scala

Solution.scala

// Start of HEAD
import org.json.simple.JSONArray
import org.json.simple.JSONObject
import org.json.simple.parser.JSONParser

import collection.JavaConversions._
// End of HEAD

// Start of Body
/**
 * TestStruct::
 *      testcase_id                   [long] ID of the test-case
 *      testcase_input_path           [String] File path to test-case input
 *      testcase_output_path          [String] File path to test-case output generated by the problem solver
 *      testcase_expected_output_path [String] File path to test-case expected output to be matched with
 *      metadata_file_paths           [ArrayList<String>] File paths to Question metadata (Extra files usually used for defining traning sets)
 *      submission_code_path          [String] File path to submission source code
 *      testcase_result               [boolean] Set to true if test-case output matches test-case expected output. Matching is done line by line
 *      testcase_signal               [long] Exit code of the test-case process
 *      testcase_time                 [double] Time taken by the test-case process in seconds
 *      testcase_memory               [long] Peak memory of the test-case process determined in bytes
 *      data                          [String] <Future use>
 *
 *
 *  ResultStruct::
 *    result      [boolean]  Assign test-case result. true determines success. false determines failure
 *    score       [double] Assign test-case score. Normalized between 0 to 1
 *    message     [String] Assign test-case message. This message is visible to the problem solver
**/

object Solution {
    def run_custom_checker(t_obj: TestStruct, r_obj: ResultStruct) {
        println("testcase_id: " + t_obj.testcase_id)
        println("testcase_input_path: " + t_obj.testcase_input_path)
        println("testcase_output_path: " + t_obj.testcase_output_path)
        println("testcase_expected_output_path: " + t_obj.testcase_expected_output_path)
        
        t_obj.metadata_file_paths.foreach((path: String) => {
            println("metadata_file_paths: " + path)  
        })
        
        println("submission_code_path: " + t_obj.submission_code_path)
        println("testcase_result: " + t_obj.testcase_result)
        println("testcase_signal: " + t_obj.testcase_signal)
        println("testcase_time: " + t_obj.testcase_time)
        println("testcase_memory: " + t_obj.testcase_memory)
        println("data: " + t_obj.data)
        
        r_obj.score = 1.0f
        r_obj.result = true
        r_obj.message = "Success"
    }
// End of Body

// Start of Tail
    def write_result_json(r_obj: ResultStruct) {
        var map = scala.collection.mutable.Map[String, Object]()
        map += ("custom_result" -> new Integer(if (r_obj.result) 1 else 0))
        map += ("custom_score" -> new java.lang.Double(if (r_obj.score > 1.0f) 1.0f else if (r_obj.score < 0.0f) 0.0f else r_obj.score))
        map += ("custom_message" -> new String(if (r_obj.message.length > 4096) r_obj.message.substring(0, 4095) else r_obj.message))
        val json_obj = new JSONObject(map)

        println(json_obj)
    }

    def main(args: Array[String]) {
        val r_obj = new ResultStruct()
      
        if (args.length < 1) {
            write_result_json(r_obj)
            System.exit(1)
        }

        val json_file_path = args(0).toString()
        var json_obj: JSONObject = null
        var t_obj: TestStruct = null

        try {
            json_obj = new JSONParser().parse(new java.io.FileReader(json_file_path)).asInstanceOf[JSONObject]
            t_obj = new TestStruct(json_obj)
        } catch {
            case _: Throwable => {
                r_obj.message = "Unable to read input json"
                write_result_json(r_obj)
                System.exit(1) 
            }
        }

        run_custom_checker(t_obj, r_obj)
        write_result_json(r_obj)
    }
}

class TestStruct(json_obj: JSONObject) {
    val testcase_id = json_obj.get("testcase_id").asInstanceOf[Long]
    val testcase_input_path = json_obj.get("input_file_path").asInstanceOf[String]
    val testcase_output_path = json_obj.get("output_file_path").asInstanceOf[String]
    val testcase_expected_output_path = json_obj.get("expected_output_file_path").asInstanceOf[String]
    val metadata_file_paths = if (json_obj.containsKey("metadata_file_paths") && json_obj.get("metadata_file_paths") != null) json_obj.get("metadata_file_paths").asInstanceOf[JSONArray].toArray().map(_.toString()) else Array[String]()
    val submission_code_path = json_obj.get("submission_code_path").asInstanceOf[String]
    val testcase_result = json_obj.get("testcase_result").asInstanceOf[Boolean]
    val testcase_signal = json_obj.get("testcase_signal").asInstanceOf[Long]
    val testcase_time = json_obj.get("testcase_time")
    val testcase_memory = json_obj.get("testcase_memory").asInstanceOf[Long]
    val data = json_obj.get("data").asInstanceOf[String]
}

class ResultStruct {
    var result: Boolean = false
    var score: Double = 0.0f
    var message: String = "Uninitialized"
}
// End of Tail

Testing:
Input file data. Path to be passed as command line argument

{"testcase_id":0,"input_file_path":"/run-XX/input00.txt","output_file_path":"/run-XX/output00.out","expected_output_file_path":"/run-XX/output_expected00.out","metadata_file_paths":["/run-XX/training.txt","/run-XX/training2.txt"],"submission_code_path":"/run-XX/solution.cpp", "testcase_result":true,"testcase_signal":0,"testcase_time":1.2,"testcase_memory":312322,"data":"Data"}

Expected output:

testcase_id:  0
testcase_input_path:  /run-XX/input00.txt
testcase_output_path:  /run-XX/output00.out
testcase_expected_output_path:  /run-XX/output_expected00.out
metadata_file_paths:  /run-XX/training.txt
metadata_file_paths:  /run-XX/training2.txt
submission_code_path:  /run-XX/solution.cpp
testcase_result:  True
testcase_signal:  0
testcase_time:  1.2
testcase_memory:  312322
data:  Data
{"custom_result": 1, "custom_score": 1.0, "custom_message": "Success"}