Thread: Random Errors Occurring When Running Game in Eclipse

Greetings.

In order to improve my programming skills I am following Notch (Minecraft creator) creating a game he made over this past weekend called Prelude of the Chambered (called Escape during coding stages). I've been going well and getting the same results as he has but all of a sudden I am getting unexpected, random errors which Notch wasn't getting. This is stopping me from running the game.

I am getting no errors in my code, but when I press the mighty green run button, the following errors are appearing in the console.

Exception in thread "Thread-2" java.lang.ArrayIndexOutOfBoundsException: -6
	at com.mojang.escape.gui.Bitmap3D.render(Bitmap3D.java:33)
	at com.mojang.escape.gui.Screen.render(Screen.java:34)
	at com.mojang.escape.EscapeComponent.render(EscapeComponent.java:105)
	at com.mojang.escape.EscapeComponent.run(EscapeComponent.java:92)
	at java.lang.Thread.run(Unknown Source)

I have no idea why they are appearing, and how to fix them.

Help would be greatly appreciated.

Have you looked at the lines in your code where the array index goes out of bounds and determined why it gets a bad value? What code is at line 34 in Screen.java? Or line 105 in EscapeComponent.java

Originally Posted by Norm

Have you looked at the lines in your code where the array index goes out of bounds and determined why it gets a bad value? What code is at line 34 in Screen.java? Or line 105 in EscapeComponent.java

I've had these parts of the code in there for a while, I'd run it and it would work, but all of a sudden these errors are popping up which is what I find so strange about it.

at com.mojang.escape.gui.Bitmap3D.render(Bitmap3D.java:33)
pixels[x + y * width] = Art.floors.pixels[xx + yy * 64];

at com.mojang.escape.gui.Screen.render(Screen.java:34)
viewport.render(game);

at com.mojang.escape.EscapeComponent.render(EscapeComponent.java:105)
screen.render(game);

at com.mojang.escape.EscapeComponent.run(EscapeComponent.java:92)
render();

pixels[x + y * width] = ...

What are the values of x, y and width when this statement is executed?
Could the value of the expression be -6?

Originally Posted by Norm

What are the values of x, y and width when this statement is executed?
Could the value of the expression be -6?

This is the whole section.

			for (int x=0; x<width; x++) {
				double xd = (x-width/2.0)/height;
				xd *= z;
				int xx = (int) (xd + game.time*0.1)%7;
				int yy = (int) (z + game.time*0.1)%7;
 
				zBuffer[x+y*width] = z;
				pixels[x + y * width] = Art.floors.pixels[xx + yy * 64];
			}

Add a println just before the statement with the invalid index to print out the contents of all the variables used in the computing the index.

Originally Posted by Norm

Add a println just before the statement with the invalid index to print out the contents of all the variables used in the computing the index.

That only causes more errors, unless I am stupid and I;m doing it wrong.

That only causes more errors, unless I am stupid and I;m doing it wrong.

I don't see how a println statement can cause errors.
Please copy and paste here the full text of the error messages.

Originally Posted by Norm

I don't see how a println statement can cause errors.
Please copy and paste here the full text of the error messages.

I've posted all the errors on the first post and here is the specific version of each error and what line it is.

That error message was BEFORE you added the println. What about AFTER you added the println?
Where are the print outs of the values used in the line where the index value is wrong?

Did you add a println statement to the code to show the variables values?
What did it print out?

Originally Posted by Norm

That error message was BEFORE you added the println. What about AFTER you added the println?
Where are the print outs of the values used in the line where the index value is wrong?

Did you add a println statement to the code to show the variables values?
What did it print out?

I put printIn on one of the lines.

CODE LINE Before:

pixels[x + y * width] = Art.floors.pixels[xx + yy * 64];

CODE LINE After:

printIn pixels[x + y * width] = Art.floors.pixels[xx + yy * 64];

ERRORS Before:

Exception in thread "Thread-2" java.lang.ArrayIndexOutOfBoundsException: -5
	at com.mojang.escape.gui.Bitmap3D.render(Bitmap3D.java:33)
	at com.mojang.escape.gui.Screen.render(Screen.java:34)
	at com.mojang.escape.EscapeComponent.render(EscapeComponent.java:105)
	at com.mojang.escape.EscapeComponent.run(EscapeComponent.java:92)
	at java.lang.Thread.run(Unknown Source)

ERRORS After:

	println cannot be resolved to a variable
 
	at com.mojang.escape.gui.Bitmap3D.render(Bitmap3D.java:33)
	at com.mojang.escape.gui.Screen.render(Screen.java:34)
	at com.mojang.escape.EscapeComponent.render(EscapeComponent.java:105)
	at com.mojang.escape.EscapeComponent.run(EscapeComponent.java:92)
	at java.lang.Thread.run(Unknown Source)

println refers to the println method of the out variable in the System class.
You use it like this:
System.out.println("var=" + var); // print the value of var

You need to print out the values of the variables used to compute the index.

Originally Posted by Norm

println refers to the println method of the out variable in the System class.
You use it like this:
System.out.println("var=" + var); // print the value of var

You need to print out the values of the variables used to compute the index.

System.out.println("var=" + var); // pixels[x + y * width] = Art.floors.pixels[xx + yy * 64];

Like so?

No. Comments do not cause anything to print out.
Do you know what a variable is?
Do you know what variables are being used to compute the indexes to the arrays?
Those are what you should print out. Show the variables values.

Originally Posted by Norm

No. Comments do not cause anything to print out.
Do you know what a variable is?
Do you know what variables are being used to compute the indexes to the arrays?
Those are what you should print out. Show the variables values.

Urgh. Silly me. I see now. I will do now.

I understand what you are meaning for me to do, but I don't know how to put that in the code, from what I've tried I haven't been successful.

Would it be like, if my code was this?

pixels[x + y * width] = Art.floors.pixels[xx + yy * 64];

I'd make it this?

System.out.println(pixels[x + y * width] = Art.floors.pixels[xx + yy * 64]);

Do you know what a variable is?
Do you know what variables are being used to compute the indexes to the arrays?
Those are what you should print out. Show the variables' values.
The variables you should print out the values of are: x, y, width, xx and yy.
They are used to compute the indexes to the two arrays.
The index to an array is what is between the []s

What happened when you executed this statement?

System.out.println(pixels[x + y * width] = Art.floors.pixels[xx + yy * 64]);

Originally Posted by Norm

Do you know what a variable is?
Do you know what variables are being used to compute the indexes to the arrays?
Those are what you should print out. Show the variables' values.
The variables you should print out the values of are: x, y, width, xx and yy.
They are used to compute the indexes to the two arrays.
The index to an array is what is between the []s

What happened when you executed this statement?

System.out.println(pixels[x + y * width] = Art.floors.pixels[xx + yy * 64]);

Instead I did,

System.out.println(x + y + " error");

A whole lost of random number errors came out, here are only a few from the huge list.

168 error
169 error
170 error
171 error
172 error
173 error
174 error
175 error
176 error
177 error

System.out.println(x + y + " error");

The problem with the way this prints out is that you do NOT see the values of x and y. You see the sum of the variables.
Try this: System.out.println("x=" + x + ", y" + y);

What was the last values that printed out before you got the error:
ArrayIndexOutOfBoundsException: -5

Those last values are the ONLY values you are interested in. The others are not what you need to see.

What were the last values that printed out before you got the error:
ArrayIndexOutOfBoundsException: -5

Are you getting the error still?