I created a counter, it adds the score perfectly each time it removes an enemy ship. However, I wanted to make an if statement in the spawning code of the enemy ships (Inside subclass of world), as I had failed to reference the value of 'score' into the world from the 'counter' class, I decided to int the score inside the world subclass, and then reference it inside the 'counter' class. It complied without problems, but before it even starts it throws NullPointerException:
"java.lang.NullPointerException
at Counter.<init>(Counter.java:12)
at GameWorld.<init>(GameWorld.java:13)
"
The first error which is being referenced in terminal(Line 12 = line 1 in this case):
Second reference(Line 13 = line 1 in this case):
And just in case, here is the code that is adding score to counter:
int score = ((GameWorld) getWorld()).score;
/**
* Act - do whatever the Counter wants to do. This method is called whenever
* the 'Act' or 'Run' button gets pressed in the environment.
*/
public void act()
{
setImage(new GreenfootImage("Score : " + score, 24, Color.WHITE, new Color(0, 0, 0, 0)));
}
public void addScore()
{
score++;
}
Counter counter = new Counter();
/**
* Constructor for objects of class GameWorld.
*
*/
public GameWorld()
{
// Create a new world with 600x400 cells with a cell size of 1x1 pixels.
super(800, 800, 1);
prepare();
}
public Counter getCounter()
{
return counter;
} public void checkForEnemy()
{
if (getOneIntersectingObject(EnemyShip.class) != null)
{
getWorld().removeObject(getOneIntersectingObject(EnemyShip.class));
GameWorld gameworld = (GameWorld)getWorld();
Counter counter = gameworld.getCounter();
counter.addScore();
getWorld().removeObject(this);
}
}