Thread: [Solved] Null Pointer Exception :: Switch statement not working.

Hi,

First post here and pretty new to Java, so thanks in advance for your help in located what I'm sure is going to be a simple mistake. I am trying to write a basic function that loads a .txt file and turns it into objects with coordinates on the map. I have tested nearly all of the function and it appears to function properly, but when I add the "final piece" the switch statement that assigns objects my draw level function keeps getting a null pointer error which has to mean that my switch statement isn't setting all the object array properly.

// set the number of objects back to zero
numberofobjects = 0;
// reads the text in the file based on what level the player is in
file = Gdx.files.internal("levels/level" + level + ".txt");
// Use a string to store the file information to prevent overhead of streaming the file multiple times during this function
String fileinfo = file.readString();
// searches through the string to find out the number of objects needed
for(int objectcount = 0; objectcount < fileinfo.length(); objectcount++){
  if(fileinfo.codePointAt(objectcount) != 0)
    numberofobjects++;  // if its  an object then count up.
}
starttime = System.currentTimeMillis();
acceleration = new Vector2(0, 0);
if(level == 1){
  // set X and Y to the top left of the screen
  int x = 0;
  int y = Gdx.graphics.getHeight()-64;
  // resize the objects array to the number of objects in the current level
  objects = new Object[numberofobjects];
  // integer to track how many objects have been set so far
  int currentobject = 0;
  // loop through the entire string which contains all object information for the level
  for(int loop = 0; loop < fileinfo.length(); loop++){
  char temp = fileinfo.charAt(loop);
  switch(temp){
    case 0: break; // blank space
    case 1: objects[currentobject] = new Object(0, new Vector2(x, y)); currentobject++; break; // tree
    case 2: break;           
    case 3: objects[currentobject] = new Object(1, new Vector2(x, y)); currentobject++; break; // rock
    case 4: objects[currentobject] = new Object(3, new Vector2(x, y)); currentobject++; break; // water
    case 'X': position = new Vector2(x, y); break;                                     // smiley
    case 'O': objects[currentobject] = new Object(2, new Vector2(x, y)); currentobject++; break; // star
  }
  x += 64;
  if(x == Gdx.graphics.getWidth() || x > Gdx.graphics.getWidth()-64){
    x = 0;
    y -= 64;
  }
}

Exact error is java.lang.NullPointerException and it occurs at

public void drawlevel(){
  drawbackground(grasstile);
  currenttime = System.currentTimeMillis();
  batch.begin();
  for(int loopcontrol = 0; loopcontrol < numberofobjects; loopcontrol++){
    switch(objects[loopcontrol].type){
      case 0: batch.draw(treetile, objects[loopcontrol].position.x, objects[loopcontrol].position.y); break;
      case 1: batch.draw(rocktile, objects[loopcontrol].position.x, objects[loopcontrol].position.y); break;
      case 2: batch.draw(startile, objects[loopcontrol].position.x, objects[loopcontrol].position.y); break;
      case 3: batch.draw(watertile, objects[loopcontrol].position.x, objects[loopcontrol].position.y); break;
    }
  }
  font.draw(batch, ""+((currenttime - starttime)/1000f)+" seconds", 10, Gdx.graphics.getHeight()-10);
  batch.end();
}

So the error would probably be in the assignment (my first code) since this draw function is looping through all objects but finds a nullpointer or what I'm assuming is an object with no value.

Thanks again to anyone who can spot my error of my ways.

My apologies. The entire stack of errors is

java.lang.NullPointerException
at lesshardtofind.me.mygdxgame.ThisGame.drawlevel(Thi sGame.java:444) (line 444 is the line where switch(objects[loopcontrol].type) is called)
at lesshardtofind.me.mygdxgame.ThisGame.gameloop(This Game.java:222) (line 222 is where drawlevel() is called)
at lesshardtofind.me.mygdxgame.ThisGame.render(ThisGa me.java:467) (line 467 is where gameloop() is called)
at com.badlogic.gdx.backends.andriod.AndriodGraphics. onDrawFrame(AndriodGraphics.java:499)
at andriod.opengl.GLSurfaceView$GLThread.run(GLSurfac eView.java:1240)

none of these point to the real issue which is my switch statement. The error arrives when trying to access the objects array but the error exists in my assignment.

I'm not getting the right behavior from the way I'm trying to get each individual character out of the string and create an object based on its value.

I figured it out. The issue was with

for(int objectcount = 0; objectcount < fileinfo.length(); objectcount++){
  if(fileinfo.codePointAt(objectcount) != 0)
    numberofobjects++;  // if its  an object then count up.
}

This was supposed to increase the number of objects if it didn't encounter a 0 unfortunately it always increased the number of objects. This would end up with way more objects than needed and since I only would assign 61 in level 1 the drawlevel would attempt to access the other 400 something and crash.

.codeAt(index) returns an int value of Unicode of the char (same as ASCII for 0-127) so instead of != 0 it should have been != 48.
Secondly I didn't account for the fact that .txt files would have '\n' escape sequences that would qualify as != '0'.

The new function looks like

for(int objectcount = 0; objectcount < fileinfo.length(); objectcount++){
  if(fileinfo.charAt(objectcount) == '1' ||
     fileinfo.charAt(objectcount) == 'O' ||
     fileinfo.charAt(objectcount) == '2' ||
     fileinfo.charAt(objectcount) == '3')
  numberofobjects++;  // if its  an object then count up.
}

which is unfortunate that I will need to add another or statement for all 20 objects or more that will be in the final game, but it at least gets around the fact that I don't know every escape sequence and unwanted char that java may interpret out of a .txt file.