Question

I have a method to check my users input in a comment text field.

public boolean isValidComment(String commentString) {
  String expression = "[a-zA-Z0-9_ ]+";
  CharSequence inputStr = commentString;
  Pattern pattern = Pattern.compile(expression, Pattern.CASE_INSENSITIVE);
  Matcher matcher = pattern.matcher(inputStr);
  return matcher.matches();
}

This works for me, but I need to change my pattern. The user should be able to type any character with the exception of these characters: <> {} [].

How do I set up the pattern to allow everything except those above?

Answer 1

Try this:

[^\<\>\{\}\[\]]+

In ahother hand, you need to use a constant of Pattern for avoid recompiled the expression every time, something like that:

private static final Pattern MY_PATTERN = 
                                     Pattern.compile("^[^\\<\\>\\{\\}\\[\\]]+$");

And use the constant:

return MY_PATTERN.matcher(commentString).matches();