Question

is there a way in Java to convert an Integer to single digits, and vice versa. Like this:

So I have the number 345. I want to break it down to 3, 4 and 5 – three seperate numbers.

I have the numbers 3, 4 and 5. I want to put them together to make 345?

Answer 1

Well you can easily convert it to a character array, and go from there:

char[] parts = Integer.toString(value).toCharArray();
int[] digits = new int[parts.length];
for (int i = 0; i < parts.length; i++) {
  digits[i] = parts[i] - '0';
}

(You don’t really need the char array here – you could just use the string and use length() and charAt() instead of length and the indexer – but I find this clearer.)

Then to reassemble, just do the reverse – create a char[] from the digits (by adding '0' to each), then create a string from the char[], then use Integer.parseInt.