java - How to replace special characters in a string?

Question

I have a string with lots of special characters. I want to remove all those, but keep alphabetical characters.

How can I do this?

Answer 1

That depends on what you mean. If you just want to get rid of them, do this:
(Update: Apparently you want to keep digits as well, use the second lines in that case)

String alphaOnly = input.replaceAll("[^a-zA-Z]+","");
String alphaAndDigits = input.replaceAll("[^a-zA-Z0-9]+","");

or the equivalent:

String alphaOnly = input.replaceAll("[^\p{Alpha}]+","");
String alphaAndDigits = input.replaceAll("[^\p{Alpha}\p{Digit}]+","");

(All of these can be significantly improved by precompiling the regex pattern and storing it in a constant)

Or, with Guava:

private static final CharMatcher ALNUM =
  CharMatcher.inRange('a', 'z').or(CharMatcher.inRange('A', 'Z'))
  .or(CharMatcher.inRange('0', '9')).precomputed();
// ...
String alphaAndDigits = ALNUM.retainFrom(input);

But if you want to turn accented characters into something sensible that's still ascii, look at these questions:

• Converting Java String to ASCII
• Java change áé??ú to aeouu
• ń ? ň ? ? ? ? ? ? ? ? ? ? ? ? --> n or Remove diacritical marks from unicode chars