嵌套for循环内的Java越界异常

Question

this may be an easy one, but I'm getting an out of bounds exception and I'm not sure how to fix it.

Basically, I am trying to create a "table" of integer fields so that I can use them to find if all of the values in the integer fields create a magic square. The nested for loop should create up to an 8x8 square, and it will create the first row of the square, but instead it gives me an out of bounds error.

The error occurs inside of the nested for loop where I'm adding the IntegerField to the GUI.

If anyone can help, that would be great. Let me know if you need more details.

import javax.swing.*;
import BreezySwing.*;

public class Interface extends GBFrame{ 
    //Create integerField array to create input for magic square
    public IntegerField[][] magicSquare;
    //Create input button, integer field which sets size of square
    public IntegerField squareSize;
    public JButton inputSize;
    //Create check square button
    public JButton checkSquare;
    //Label to output if there is a magic square
    public JLabel squareLabel;
    //Size of square variable
    public int size;

    //CalcSquare object
    CalcSquare calc = new CalcSquare();

    //Constructor for Square interface
    public Interface()
    {
        squareSize = addIntegerField (0, 1, 1, 1, 1);
        inputSize = addButton ("Input Size", 2, 1, 1, 1);
        squareLabel = addLabel ("", 3, 1, 1, 1);
        checkSquare = addButton ("Check Square", 4, 1, 1, 1);
    }   
    //Creates IntegerFields on the GUI as needed.
    public void createFields()
    {
        for (int i = 0; i <= size; i++)
        {
            for (int x = 0; x <= size; x++)
            {
                magicSquare = new IntegerField[i][x];
    }
        }
    }

public void buttonClicked(JButton buttonObj)
{
        if (buttonObj == inputSize)
        {
            size = squareSize.getNumber();
            createFields();
            for (int i = 0; i <= size; i++)
            {
                for (int x = 0; x <= size; x++)
                {
                    magicSquare[i][x] = addIntegerField (0, i+1, x+1, 1, 1);
                }
            }   
        }
        else if (buttonObj == checkSquare)
        {       
        }
    }
}

Answer 1

A for loop condition of i <= size Should always raise red flags since if i == size, you've gone beyond the size of the array or collection. Note that arrays and collections are 0 based and go from 0 to size - 1.

It should instead almost always be i < size

Answer 2

All your loops are iterating upto size which will cause ArrayIndexOutOfBoundException. The Array index starts from 0 to size-1 . Here is one of such loop in your code:

for (int i = 0; i <= size; i++)

you need to iterate the loop only till size

for (int i = 0; i < size; i++)

Correct other loops accordingly

Answer 3

size is never initialized. And your <= should be < in the for loops.

In fact, if you're using size as a constant to set the size of your arrays, you should use i < size - 1 in for loops.