Writing data to a text file from Arduino using Processing

I am currently trying to get a value (Yes!) from the Arduino to a text file (data.txt).

The problem is that the data isn't being read from the Arduino's Serial. When I tried to simple print the value to the prompt in processing, I came out empty handed.

Below is my code for the Arduino

//Just a basic program to write to the Serial the word/phrase; `Yes!`.

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  Serial.println("Yes!");
}

Below is my code for processing:

import processing.serial.*;
Serial mySerial;
PrintWriter output;
void setup() {
   mySerial = new Serial( this, Serial.list()[0], 9600 );
   output = createWriter( "data.txt" );
}
void draw() {
    if (mySerial.available() > 0 ) {
         String value = mySerial.readString();
         if ( value != null ) {
              output.println( value );
         }
    }
}

void keyPressed() {
    output.flush();  // Writes the remaining data to the file
    output.close();  // Finishes the file
    exit();  // Stops the program
}

Yes, this code was found from this stackoverflow question.

Any help would be greatly appreciated!