Car Robot Bluetooth Control Android

int IN1 = 6;
int IN2 = 5;
int IN3 = 4;
int IN4 = 3;
int ENA = 7;
int ENB = 2;

String str;
int blueToothVal;


void setup()
{
  Serial.begin(9600);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
  pinMode(ENA, OUTPUT);
  pinMode(ENB, OUTPUT);
}
void loop()
{
  bluetooth();
}




void bluetooth()
{
  while (Serial.available())                             // Read bluetooth commands over Serial1 // Warning: If an error with Serial1 occurs, make sure Arduino Mega 2560 is Selected
  {
    {
      str = Serial.readStringUntil('\n');               // str is the temporary variable for storing the last sring sent over bluetooth from Android device
      //Serial.print(str);
    }

    blueToothVal = (str.toInt());                        //  convert the string 'str' into an integer and assign it to blueToothVal

    switch (blueToothVal)
    {
      case 1:
        FRONT();
        delay(10);
        break;

      case 2:
        BACKWARDS();
        delay(10);
        break;

      case 3:
        LEFTT();
        delay(10);
        //STOP();
        break;

      case 4:
        RIGHTT();
        delay(10);
        //STOP();
        break;

      case 5:
        STOP();
        break;

    }                                                              // end of switch case

  }                                                              // end of while loop Serial1 read


}

void STOP() {
  digitalWrite(IN1, 0);
  digitalWrite(IN2, 0);

  digitalWrite(IN3, 0);
  digitalWrite(IN4, 0);

  digitalWrite(ENA, LOW);
  digitalWrite(ENA, LOW);
}

void FRONT() {
  digitalWrite(IN1, 0);
  digitalWrite(IN2, 1);

  digitalWrite(IN3, 1);
  digitalWrite(IN4, 0);

  digitalWrite(ENA, HIGH);
  digitalWrite(ENB, HIGH);
}

void BACKWARDS() {
  digitalWrite(IN1, 1);
  digitalWrite(IN2, 0);

  digitalWrite(IN3, 0);
  digitalWrite(IN4, 1);

  digitalWrite(ENA, HIGH);
  digitalWrite(ENB, HIGH);
}

void RIGHTT() {
  digitalWrite(IN1, 0);
  digitalWrite(IN2, 1);

  digitalWrite(IN3, 0);
  digitalWrite(IN4, 1);

  digitalWrite(ENA, HIGH);
  digitalWrite(ENB, HIGH);
  //delay(100);
}

void LEFTT() {
  digitalWrite(IN1, 1);
  digitalWrite(IN2, 0);

  digitalWrite(IN3, 1);
  digitalWrite(IN4, 0);

  digitalWrite(ENA, HIGH);
  digitalWrite(ENB, HIGH);
  //delay(100);
}