Your regex is good altough I would replace it with the empty string
String resultString = subjectString.replaceAll("[\t\n\r]", "");
You expect a space between "text." and "And" right?
I get that space when I try the regex by copying your sample
"This is my text. "
So all is well here. Maybe if you just replace it with the empty string it will work. I don't know why you replace it with \s. And the alternation | is not necessary in a character class.