I get a string from a 3rd party library, which is not well encoded. Unfortunately I\'m not allowed to change the library or use another one...
So the actual problem
Well, very strange:
As
byte[] b = resultString.getBytes("Shift_JIS");
String value = new String(b, "UTF-8");
didn't work for me I tried the following:
String value = new String(resultString.getBytes("SHIFT-JIS"), "UTF-8")
Works like a charm. Maybe it was because of the underscore and lower case character in "Shift_JIS".