Error message Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException:

Question

I have this code but i keep getting this error message and i dont know why?

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2 at javaapplication28.JavaApplication28.main(JavaApplication28.java:38) 1 2 Java Result: 1

public static void main(String[] args) {   

    Scanner input = new Scanner(System.in);
        System.out.println("This program transposes a matrix.");
        System.out.println("Please enter the number of rows");
        int rows = input.nextInt();
        System.out.println("User enters: "+rows);
        System.out.println("Please enter the number of columns");
        int columns = input.nextInt();
        System.out.println("User enters: "+columns);
        int [][]matrix=new int[rows][columns];
        for(int i=0;i<matrix.length;i++){
            for(int j=0;j<matrix[i].length;j++){
             System.out.print("Enter value for row [" +i+ "] column [" +j+"]:");
                matrix[i][j]=input.nextInt();  
            }
        }
        for(int i=0;i<=matrix.length;i++){
             System.out.println();
             for(int j=0;j<=matrix.length;j++){
                 System.out.print(matrix[i][j]+"  ");           
             }
         }
        System.out.println("The transpose of this matrix has" +columns+"rows and"+rows+"columns and the transpose is:");
        for(int i=0;i<=matrix.length;i++){
             System.out.println();
             for(int j=0;j<=matrix.length;j++){
                 System.out.print(matrix[j][i]+"  ");
    }
}}
}

Maxim Shoustin · Accepted Answer · 2012-11-08 20:28:38Z

3

You run in loop from 0 to length+1 i<=matrix.length. Remove = from for statement and on internal loop add: matrix[i].length instead matrix.length to get column count and not row.

Here is valid code:

for(int i=0;i<matrix.length;i++){
        System.out.println();
        for(int j=0;j<matrix[i].length;j++){
            System.out.print(matrix[i][j]+"  ");           
        }
    }
    System.out.println("The transpose of this matrix has" +columns+"rows and"+rows+"columns and the transpose is:");
    for(int i=0;i<matrix.length;i++){
        System.out.println();
        for(int j=0;j<matrix[i].length;j++){
            System.out.print(matrix[j][i]+"  ");
        }
    }}

edited Nov 8, 2012 at 20:28

answered Nov 8, 2012 at 20:10

Maxim Shoustin

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3 Comments

Jim Garrison Over a year ago

For the general case (ragged array) shouldn't that be j<matrix[i].length?

Jim Garrison Over a year ago

Also, the transpose code is wrong, you can't just swap the indexes like that in the general case unless the matrix is always square.

Maxim Shoustin Over a year ago

@JimGarrison well, if you entered to second for i=0; so you can use i or 0. The same thing. True, that to use indexes is not good technique. For this example he has square matrix. Otherwise i could write by other way.

Francisco Alvarado · Accepted Answer · 2012-11-08 20:27:55Z

0

If you start your for cycle index iterators at 0 you should use < and not <= when it's the length of an array, because otherwise it would be as if you're trying to get the (n+1)th element of the (size n) array what it's causing the ArrayIndexOutOfBoundsException exception

answered Nov 8, 2012 at 20:27

Francisco Alvarado

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