Aaa now I understood what you mean. it wasn't stacking in the first test it was stacking in 0 :D. sorry that I have waste your time. and thank you for your help.

i was going to add if statement at the beginning of the code for that. my problem is that i cannot even run program for solving this:

assertEquals("128.114.17.104", Kata.longToIP(2154959208L)

So I have changed my solution to more static/brute force method to test.

There's an error in your code. Recreate this test case locally and see how it fails:

assertEquals("0.0.0.0", Kata.longToIP(0));

Use markdown formatting

Sorry I ve never shared my code before in this platform i dont know why it looks so weird

I tried both, Java 8 and Java 11. If you think your solution is OK and tests are incorrect, you can post your solution here (with spoiler flag!) and we will check it.

Well thank you for your replay but when i printed out my solution it was matching with his answer. I can try to solve it again. which version of java did u use?

There is a problem with String index out of range: when you solve the problem, in Java. There is no problem with String index out of range: when I solve the problem, in Java.

There is a problem with String index out of range: when u solve the problem, in Java