String.replaceAll Strange Behaviour

Question

String s = "hi                  hello";
s = s.replaceAll("\\s*", " ");
System.out.println(s);

I have the code above, but I can't work out why it produces

 h i  h e l l o 

rather than

 hi hello

Many thanks

Answer 1

Use + quantifier to match 1 or more spaces instead of *: -

s = s.replaceAll("\\s+", " ");

\\s* means match 0 or more spaces, and will match an empty character before every character and is replaced by a space.

Answer 2

The * matches 0 or more spaces, I think you want to change it to + to match 1 or more spaces.