class Walker {

  int x;

  int y;

  Walker() {

    x = width/2;

    y = height/2;

  }

  void display() {

    stroke(0);

    point(x,y);

  }

  void step() {

    int choice = int(random(4)); //0,1,2,or 3

    if(choice == 0) {

      x++;

    } else if(choice == 1) {

      x--;

    } else if(choice == 2) {

      y++;

    } else {

      y--;

    }

  }

}

Walker walker;

void setup() {

  size(640,360);

  walker = new Walker();

  background(255);

}

void draw() {

  walker.setup();

  walker.display();

}