How can I invert the case of a String in Java?

Question

I want to change a String so that all the uppercase characters become lowercase, and all the lower case characters become uppercase. Number characters are just ignored.

Answer 1

Java 8 and above:

String myString = "MySampleString123";
System.out.println(myString.chars().map(c -> Character.isLetter(c) ? c ^ ' ' : c).collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append).toString());

Code which is inverting the case of letter, is important to notice:

Character.isLetter(c) ? c ^ ' ' : c