Very Easy Arduino and Android Voice control Robot ( How to make a voice control robot)

Required Components:

Arduino Uno 
Bluetooth Module
L293D Motor Driver
2x Gear Motor
2x Wheel
1x Chasis
A breadboard 
Connecting wires

Arduino Program for voice control robot.
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#include <SoftwareSerial.h>

SoftwareSerial BT(10, 11); //TX, RX respetively
String readvoice;

void setup() {
 BT.begin(9600);
 Serial.begin(9600);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);

}
//-----------------------------------------------------------------------// 
void loop() {
  while (BT.available()){  //Check if there is an available byte to read
  delay(10); //Delay added to make thing stable
  char c = BT.read(); //Conduct a serial read
  readvoice += c; //build the string- "forward", "reverse", "left" and "right"
  } 
  if (readvoice.length() > 0) {
    Serial.println(readvoice);

  if(readvoice == "forward")
  {
    digitalWrite(3, HIGH);
    digitalWrite (4, HIGH);
    digitalWrite(5,LOW);
    digitalWrite(6,LOW);
    delay(100);
  }

  else if(readvoice == "reverse")
  {
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, HIGH);
    digitalWrite(6,HIGH);
    delay(100);
  }

  else if (readvoice == "right")
  {
    digitalWrite (3,HIGH);
    digitalWrite (4,LOW);
    digitalWrite (5,LOW);
    digitalWrite (6,LOW);
    delay (100);
  
  }

 else if ( readvoice == "left")
 {
   digitalWrite (3, LOW);
   digitalWrite (4, HIGH);
   digitalWrite (5, LOW);
   digitalWrite (6, LOW);
   delay (100);
 }

 else if (readvoice == "stop")
 {
   digitalWrite (3, LOW);
   digitalWrite (4, LOW);
   digitalWrite (5, LOW);
   digitalWrite (6, LOW);
   delay (100);
 }
readvoice="";}} //Reset the variable