array index out of bounds in counting for "true" boolean values in java

Question

Please help. I'm having an indexArrayOutOfBounds in my code. what's wrong with this? the compiler says the error occurs at the if ststement.

private void tableTest(){
        int nRow = sampleTable.getRowCount();
        int nCol = sampleTable.getColumnCount();
        int counter = 0;
        int j, i;

        Object[][] tableData = new Object[nRow][nCol];
        for (i = 0 ; i < nRow ; i++){
            for (j = 3 ; j < nCol ; j++){
                tableData[i][j] = sampleTable.getValueAt(i,j);
                System.out.println(tableData[i][j]);
                //if(counter)
                //    Arrays.deepToString(tableData[i][j]);
            }
            System.out.println("end");
            if(tableData[i][j].equals(true)){
                counter++;
                System.out.print(counter);
            }
        }

    }

Answer 1

You need that if block to be inside the inner for loop, or the indexes don't match to anything in the array.

Currently, that if statement runs when j has already reached nCol, which means it has exceeded the bounds of the array.

To fix this, remove the } from the line below the comments, and add a } right at the end. This effectively moves the if block up into the inner loop.

Update

You might get a null pointer exception calling equals on references in the array that have not been assigned an object. You should probably change the if condition to say this.

if(tableData[i][j] != null && tableData[i][j].equals(true)){

Answer 2

Once your inner loop :for (j = 3 ; j < nCol ; j++){} terminates, the value of j = nCol. When you try to access element tableData[i][j] in your if condition, you are trying to reach to a memory location out of the bounds of the array.