matrix

class Main{
     static void print(int num) {
        String str = Integer.toString(num);
        String s = String.format("%3s", str);
        System.out.print(s);
    }

    public static void main(String args[]) {
        int[][] arr = {
            {1,2,3,4,5},
            {6,7,8,9,10},
            {11,12,13,14,15},
            {16,17,18,19,20},
            {21,22,23,24,25}};

        int i=0, j=0, length=4;

        System.out.println("Original Matrix");
        for (i=0; i<5; i++) {
            for (j=0; j<5; j++) {
                print(arr[i][j]);
            }
            System.out.println();
        }

        System.out.println("\nInterchanging primary diagonal with secondary");
        for (i=0; i<5; i++) {
            for (j=0; j<5; j++) {
                if (i==j) {
                    print(arr[i][length-i]);
                }
                else if (j == length-i) {
                    print(arr[i][i]);
                }
                else {
                    print(arr[i][j]);
                }
            }
            System.out.println();
        }

        System.out.println("\nInterchanging upper triangle with lower");
        for (i=0; i<5; i++) {
            for (j=0; j<5; j++) {
                if (i + j > length || i + j < length){
                    print(arr[length-i][length-j]);
                }
                else {
                    print(arr[i][j]);
                }
            }
            System.out.println();
        }

        System.out.println("\nInterchanging left triangle with right");
        for (i=0; i<5; i++) {
            for (j=0; j<5; j++) {
                if (i + j < i+i || i + j > i+i){
                    print(arr[j][i]);
                }
                else {
                    print(arr[i][j]);
                }
            }
            System.out.println();
        }
    }
}