Null Pointer exception

Chris4942

Whenever I try to run this I get the addObstacle function I get a NullPointerException error. Please help.

ArrayList<Level> levels;

class Level{

  ArrayList<Obstacle> obstacles;

  Level(){
  }

  void load(){
  }

  void addObstacle (float x1 , float y1 , float x2 , float y2 , int t){
    obstacles.add (new Obstacle (x1 , y1, x2 , y2, t));
  }
}

GoToLoop

http://forum.processing.org/two/discussion/8045/how-to-format-code-and-text

MenteCode

Can you put up the Obstacle class? We don't really know what you're doing in there.

koogs

i don't think we need that tbh.

line 5 is not enough to create an ArrayList. you need to assign the result of new ArrayList(); to it somewhere (maybe even line 5 itself)

GoToLoop

// forum.processing.org/two/discussion/9538/null-pointer-exception

import java.util.List;

class Level {
  final List<Obstacle> obstacles = new ArrayList<Obstacle>();

  void addObstacle(float x1, float y1, float x2, float y2, int t) {
    obstacles.add(new Obstacle(x1, y1, x2, y2, t));
  }
}

class Obstacle {
  float x1, y1, x2, y2;
  int t;

  Obstacle(float $x1, float $y1, float $x2, float $y2, int $t) {
    x1 = $x1;
    y1 = $y1;
    x2 = $x2;
    y2 = $y2;
    t = $t;
  }
}