More trouble with classes and arrays

Okay, I got this file:
globals.java:

Code:

---

public class globals {
        static public frame frames[] = new frame[maxFramesAllowed];                // Holds the grid data, maximum of 1000 frames right now
       
        static public class frame {
                public cell cells[] = new cell[maxCellsAllowed];
                public char nextFreeCell = 0;
                public char delay = 1;
               
                public frame() {
                        // nothing
                }
               
                public frame(int frameDelay) {
                        delay = (char) frameDelay;
                }
               
                public frame(char frameDelay) {
                        delay = frameDelay;
                }
        }
       
        static public class cell {
                public char x;
                public char y;
                public char value;
               
                public cell(int xVal, int yVal, int val) {
                        x = (char) xVal;
                        y = (char) yVal;
                        value = (char) val;
                }
               
                public cell(char xVal, char yVal, char val) {
                        x = xVal;
                        y = yVal;
                        value = val;
                }
        }
}

---

When I ran it with the regular portion of my program, I got errors about null pointers/objects.

So iIcreated this program to test the class:
TEST_globals.java

Code:

---

public class TEST_globals {
        public globals g;
       
        public static void main(String argv[]) {
                for (int i = 0; i < 5; i++) {
                        globals.frames[i] = new globals.frame(i * 2);
                        System.out.println("Delay for frame[" + i + "]: " + globals.frames[i].delay);
                       
                        for (int j = 0; j < 5; j++) {
                                System.out.println("\tFor frame[" + i + "], next free cell at[" + globals.frames[i].nextFreeCell + "]");
                                globals.frames[i].cells[globals.frames[i].nextFreeCell] = new globals.cell(j, j, i * j);
                                globals.frames[i].nextFreeCell++;
                        }
                }
        }
}

---

The result:
http://oi51.tinypic.com/2lcmi9t.jpg

Please help. :(

Before I read and respond I just wanted to point out that you forgot the [ code] part of your first snippet.

Also, I am not really sure what you are asking, would you mind clarifying your question for me?

What I want is for my data, when I access it, not to turn up as a "null", as it is doing right now.

Others may have better advice, but are you adding information to the cells?

Yeah, I am going to, but I'm trying to fix the issue with the null data first.

If you try to access an array element before you fill it you will get a null pointer exception. If you create the array and don't fill the array and try to do anything with the items in the array, it will cause a null pointer exception. Can you show me the code that generate the null pointer exception and the stack trace?

You mean this, I also have declared in "globals.java":

Code:

---

static public int maxFramesAllowed = 10;    // Small right now for simplicity
static public frame frames[] = new frame[maxFramesAllowed];

---

A stack trace looks something like this

Code:

---

Exception in thread "main" java.lang.NullPointerException
        at TestArray.main(testarray.java:5)

---

And lets us see what causes the problems. Is the above the code that was giving you null errors?

Normally when you get a null error it's cause by trying to do something on an object that hasn't been instantiated. Here is a small example I created which causes a NullPointerException

Code:

---

public class TestArray{
        public static void main(String[] args){
                Object[] x = new Object[5];
                for(int i = 0; i < x.length; ++i){
                        System.out.println(x[i].toString());
                }
        }
}

---

To avoid null pointers you need to fill the array. In the above example you would do something like this

Code:

---

public class TestArray{
        public static void main(String[] args){
                Object[] x = new Object[5];
                for(int i = 0; i < x.length; ++i){
                        x[i] = new Object();
                }
                for(int i = 0; i < x.length; ++i){
                        System.out.println(x[i].toString());
                }
        }
}

---

From the fact that you are receiving null pointer exceptions, I am assuming you are attempting to call methods on an array with items that have not been initialized. Like I said, this is an assumption.

Quote:

---

Originally Posted by CuddlyKittens11

You mean this, I also have declared in "globals.java":

Code:

---

static public int maxFramesAllowed = 10;    // Small right now for simplicity
static public frame frames[] = new frame[maxFramesAllowed];

---

---

So what you have there is an array of 10 references to frame objects. Each one of those references is null. You have to fill the array, like this:

Code:

---

for(int i = 0; i < frames.length; ++i)
    frames[i] = new frame(...);

---

BTW... it'll be very helpful to you later, as well as helpful to anyone reading your code, if you adopt the standard Java conventions for naming and capitalization.

Hey guys, I figured out my problem, it had something to do with the char datatypes I was using.

Thanks though.