Why 0010 give different result in array in java

Question

If I placed 00 or 0 before digits values in array output become different.

 int arr[][]=new int[3][2];
    arr[0][0]=00;
    arr[0][1]=01;
    arr[1][0]=10;
    arr[1][1]=0011;
    arr[2][0]=0020;
    arr[2][1]=21;
    for(int a[]: arr){
        for(int c : a){
            System.out.println(c);
        }

    }

Output is : 0 1 10 9 16 21

Answer 1

A number with a leading zero is treated as Octal.

Your 0011 is octal 8 + 1 = 9, 0020 is 2 * 8 = 16.

Note that your 00 and 01 are also being interpreted in Octal but they just happen to be the same value as their decimal counterparts.