Please I Help Me for My Code

How to solve the following problem in a java programming? Please help and Thank you very much.

Suppose I have a number like this

420815722

I then grouped these into 1-digit numbers and 2 and so on,
so that it becomes

4 20 8 15 7 22

then every two digits are added together, so it becomes:

4 (2 +0) 8 (1 +5) 7 (2 +2)

the results

4 2 8 6 7 4

Well first I'll suggest getting whatever number you're working with into a String; that way you can easily manipulate the characters. After that, you will probably need to make use of the <String>.substring() method and possible some sort of loop.

Have you started with any code at all? If you have, please post it here.