Error: NumberFormatException whilst running code.

public static void main(String[] args) {
    Console console = System.console();
    String startingProcedure = console.readLine("You started this program so I guess you want to calculate the forceOfGravity .. ? Type 'Y' if that is what you want if not press any other key :");
    if (startingProcedure.equalsIgnoreCase("y")) {
      String heightl = console.readLine("What is the height of the object toward the ground (in meters):");
      int height = Integer.parseInt("heightl");
      String weightl = console.readLine("What is the weight of the ball (in kilograms):");
      int weight = Integer.parseInt("weightl");
      String onEarth = console.readLine("Are you on earth right now ? .. :");

      if(onEarth.equalsIgnoreCase("y") || onEarth.equalsIgnoreCase("yes")) {
       Ball ball = new Ball(weight, height, 10);
       ball.calculateForce();
      }
      else {
       System.exit(0);  
      }

    }
    else {
      System.exit(0);
    }