Edit character in text file

Processing Beginners
3

Here’s an example how to save some stuff (ie game score):

int xpos;
int ypos;
boolean[] keys = {false, false, false, false};

void setup(){
  fullScreen();
  loadStuff();
}

void draw(){
  background(0);
  
  if(keys[0]){
    ypos -= 5;
  }
  if(keys[1]){
    ypos += 5;
  }
  if(keys[2]){
    xpos += 5;
  }
  if(keys[3]){
    xpos -= 5;
  }
  
  rect(xpos, ypos, 50, 50);
}

void keyPressed(){
  switch(keyCode){
    case UP:
    keys[0] = true;
    break;
    case DOWN:
    keys[1] = true;
    break;
    case RIGHT:
    keys[2] = true;
    break;
    case LEFT:
    keys[3] = true;
    break;
  }
}

void keyReleased(){
  switch(keyCode){
    case UP:
    keys[0] = false;
    break;
    case DOWN:
    keys[1] = false;
    break;
    case RIGHT:
    keys[2] = false;
    break;
    case LEFT:
    keys[3] = false;
    break;
  }
}

// Save if we exit the sketch
void exit(){
  saveStuff();
  super.exit();
}

// This is what you're looking for
void loadStuff(){
  try{
    String[] stuff = loadStrings(System.getProperty("user.home") + File.separator + "stuff.txt");// Can be any file type
    xpos = int(stuff[0]);
    ypos = int(stuff[1]);
  }catch(Exception e){
    println("File doesn't exist!");
  }
}

void saveStuff(){
  String[] stuff = {str(xpos), str(ypos)};
  saveStrings(System.getProperty("user.home") + File.separator + "stuff.txt", stuff);
}