Regex is actually slower.

Interesting. I am unsure why this is best practice when Java gives us regex out of the box. Cyclomatic complexity of this vs anything using regex.

i was going to do this, but it made me lazy xd

Performancewise would be "better" to use a StringBuilder or StringBuffer (using the .append() method) as it is faster to reallocate memory for a growing object, than creating a new object in each loop iteration.

Please use spoiler flag next time.

Using a regex would be faster, but this solution works.