java number split

sup javafags,
how can I split a 50 character long number into blocks of 5?

I created a random number generator to generate me a long block of 50 random numbers, but I need to break it all up in blocks of 5 so I have 10 blocks of 5 numbers.

How can I do this?


void homework(String str){
    int parts[10];
    for(int i=0; i<10; ++i)
        parts[i] = str.substring(i*5, (i+1)*5);
    ...