Question

How do I trim spaces inside leaving only one space taking consideration of performance?

Input:
     AA     BB
Output:
AA BB

Input:
A      A
Output:
A A

Answer 1

System.out.println("     AA     BB".replaceAll("\\s+", " ").trim());

Output:

AA BB

Note: Unlike some of the other solutions here, this also replaces a single tab with a single space. If you don’t have any tabs you can use ” {2,}” instead which will be even faster:

System.out.println("     AA     BB".replaceAll(" {2,}", " ").trim());