\s is a shortcut for whitespace characters in regex. It has no meaning in a string. ==> You can’t use it in your replacement string. There you need to put exactly the character(s) that you want to insert. If this is a space just use
" " as replacement.
The other thing is: Why do you use 3 backslashes as escape sequence? Two are enough in Java. And you don’t need a
| (alternation operator) in a character class.
L is not changed. If you want to have a result you need to do
String result = L.replaceAll("[\\t\\n\\r]+"," ");
String in = "This is my text.\n\nAnd here is a new line"; System.out.println(in); String out = in.replaceAll("[\\t\\n\\r]+"," "); System.out.println(out);