Out of bounds error:

[sarevok9]

I have the following method, it takes in an x / y variable that correlate to a position on a 10x10 2d array, the method simply checks to see if a spot is empty, if it is, it needs to do one thing, if it's not, it undoes everything up to that point.

Here's my code

public void AddVert(int x, int y, int z, char Letter) {
        int i, j;
        for (i=0; i<z; i++){
            if (Arrays[y][x]!=' '){
                System.out.println("Oh dear, it seems as though there is a collision at location: "Location.ReverseLoc(y, x)+ "Please try another location");
                for (j=0; j<i; j++){
                    if (i > 0){
                        y--;
                        Arrays[y][x]=' ';
                    }
                    else if (i<=0){
                        //Null
                    }
                }
            }
            else {
                Arrays[y][x]= Letter;
                y++;
            }

This generates if the values passed into it are 0,0 and 0,1 (which works) then testing at 0,0 - 0,1 - 0,2 which generates the following compiler output.

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
Oh dear, it seems as though there is a collision at location: a1Please try another location
at Arrays.AddVert(Arrays.java:21)
at Test.main(Test.java:152)
Java Result: 1

Contents of Test.main line 152

Object.AddVert(x,y,health,letter);

Value in x = 0, y= 0, health = 3, letter = 'S' (Char s).


Any help with my logic on this would be delightful.

[KevinWorkman]

Have you stepped through this with a debugger to follow what's going on?

[sarevok9]

Have you stepped through this with a debugger to follow what's going on?

Sad, simple truth here, I never learned how to use the debugger in netbeans. I can for my c++ class but I've never needed to (until now) for java / netbeans. Know of a tutorial for it?

[milovan]

if (Arrays[y][x]!=' '){
        for (j=0; j<i; j++){
                 if (i > 0){
                        y--;

First position in Array is 0, second positon is 1, third position is 2 and so on.
If you set

Array[0][0]

it reffers to very first position. Now when you set

y--;

it means you are looking for

Array[-1][0]

which is impossible, the y position can not be lower than 0

You must think of your logic once again...

[sarevok9]

if (Arrays[y][x]!=' '){
        for (j=0; j<i; j++){
                 if (i > 0){
                        y--;

First position in Array is 0, second positon is 1, third position is 2 and so on.
If you set

Array[0][0]

it reffers to very first position. Now when you set

y--;

it means you are looking for

Array[-1][0]

which is impossible, the y position can not be lower than 0

You must think of your logic once again...

The basic premise of the code is to be able to take any spot on a 10x 10 grid and be able to place / undo anything that might be placed then cause a collision.

In this case I am checking at spot 0 / 0. During the first pass through of this loop, i should be = to 0, but the spot Arrays[y][x] should not be equal to 0. For some reason

if (i > 0){

is triggering instead of

else if (i<=0){

And I cannot for the LIFE of me figure out why?

[Zack]

How come you provided a code that doesn't compile?

I mean...
System.out.println("Oh dear, it seems as though there is a collision at location: "Location.ReverseLoc(y, x)+ "Please try another location");
That line has invalid syntax. (No + before "Location".) Can we see the EXACT code you are using?

Other than that, I can only think that i>0 because i loops for any value <z, which is 3... so, i will be 0, 1, 2.

I'd like to be able to run your code, but I'm not sure what Arrays is (or the rest of the class).

[sarevok9]

How come you provided a code that doesn't compile?

I mean...
System.out.println("Oh dear, it seems as though there is a collision at location: "Location.ReverseLoc(y, x)+ "Please try another location");
That line has invalid syntax. (No + before "Location".) Can we see the EXACT code you are using?

Other than that, I can only think that i>0 because i loops for any value <z, which is 3... so, i will be 0, 1, 2.

I'd like to be able to run your code, but I'm not sure what Arrays is (or the rest of the class).

Here's the most recent revisions of the code :
BattleShip.java -- BattleShip.java - Pastebin.com
Boatloc.java -- Boatloc.java - Pastebin.com
Arrays.java -- Arrays.java - Pastebin.com
Boat.java -- Boat.java - Pastebin.com

[Zack]

Ok, I see what you're driving at now. I hate working with boards; my checkers game drove me nuts trying to do this all right.

I'd rework the method, honestly. Try an approach like this (for the vertical; swap y for x when doing the horizontal); note that this is in pseudocode mostly:

if (y <= (boardHeight - z)) { return; } // y is too large to fit the piece on the board
int y2 = y, z2 = z;
while (z2 > 0) { // for each health
    check if Arrays[y][x] == ' ', if not, you need to end the function, cause the piece can't go here
    y2++
    z2--
}
z2 = z; y2 = y;
while (z2 > 0) { // same loop again; the first one was just to check if ALL squares were valid first
    Arrays[y][x] = boatLetter
    y2++
    z2--
}

I think that kind of idea should do it. Basically, you're checking first to see it the Y value is valid--that is, is it small enough that the highest amount of positions it will cover are all on the board? If not, return the function--it won't work.

Next, check all the squares that the boat will cover. Are any occupied? If not, you have a collision (which you can say in a message), and the function won't work, so it has to return.

Finally, place the boat, using the same logic as the checking.

I'd make this a boolean function, so you can return false if it wasn't placed and true if it was. Then the user can place it again if he or she has to.

EDIT: You could also compact the logic in the while loop to be, "while (y2 < y + z)", but I'd make sure you can get everything working before you worry about compacting/devariablizing it.

[sarevok9]

Ok, I see what you're driving at now. I hate working with boards; my checkers game drove me nuts trying to do this all right.

I'd rework the method, honestly. Try an approach like this (for the vertical; swap y for x when doing the horizontal); note that this is in pseudocode mostly:

if (y <= (boardHeight - z)) { return; } // y is too large to fit the piece on the board
int y2 = y, z2 = z;
while (z2 > 0) { // for each health
    check if Arrays[y][x] == ' ', if not, you need to end the function, cause the piece can't go here
    y2++
    z2--
}
z2 = z; y2 = y;
while (z2 > 0) { // same loop again; the first one was just to check if ALL squares were valid first
    Arrays[y][x] = boatLetter
    y2++
    z2--
}

I think that kind of idea should do it. Basically, you're checking first to see it the Y value is valid--that is, is it small enough that the highest amount of positions it will cover are all on the board? If not, return the function--it won't work.

Next, check all the squares that the boat will cover. Are any occupied? If not, you have a collision (which you can say in a message), and the function won't work, so it has to return.

Finally, place the boat, using the same logic as the checking.

I'd make this a boolean function, so you can return false if it wasn't placed and true if it was. Then the user can place it again if he or she has to.

EDIT: You could also compact the logic in the while loop to be, "while (y2 < y + z)", but I'd make sure you can get everything working before you worry about compacting/devariablizing it.

I think that I understand what you're getting at here, I'll toss up my code tomorrow night and see if it both works and / or needs more help, thanks for the suggestion so far, and trust me, I TOTALLY feel your pain on working with a game board.... HUGE mistake.

[sarevok9]

I'll be marking this as solved for now, since I found a simple solution to this. In case anyone ever looks at this in the future:

I changed the call to my method to be a bool switch and changed the placement method to a boolean rather than a void.


BattleShip.java

//Vertical if Orientation
boolean addboat=false;
if (iOrientation == 1){ // If orientation is vertical
addboat= MyPlayers.AddBoatVert(x,y,SelectedBoat.health,SelectedBoat.letter);// Add boat letter at selected location
if (addboat == false){
    SelectedBoat.used -=1;
}// addboat = false
}// End vert orientation if

Arrays.Java

 public boolean AddBoatVert(int x, int y, int z, char boatLetter) {
        int i, j;
        boolean booladdboat=true;
        for (i=0; i<z; i++){ // while I < SelectedBoat.health (z), increment i
            if (Arrays[y][x]!=' '){ // if X / y do not = default value
                System.out.println("Oh dear, it seems as though there is a collision at location: "+Boatloc.ReverseBoatLoc(y, x)+ "Please try another location");// There is a collision at location x/y
                booladdboat=false; 
                return booladdboat;
            }
            else { // otherwise....
                Arrays[y][x]= boatLetter;
                y++;
            }
        }// End for
        return booladdboat;
    }