Remove all characters from string which are not on whitelist

character, java, regex, replace, whitelist

Solution

Yes, you can use `String.replaceAll` which takes a regex:

String input = "BAD good {} []";
String output = input.replaceAll("[^a-z0-9\\[\\]]", "");
System.out.println(output); // good[]

Or in Guava you could use a `CharMatcher`:

CharMatcher matcher = CharMatcher.inRange('a', 'z')
                          .or(CharMatcher.inRange('0', '9'))
                          .or(CharMatcher.anyOf("[]"));
String input = "BAD good {} []";
String output = matcher.retainFrom(input);

That just shows the lower case version, making it easier to demonstrate. To include upper case letters, use `"[^A-Za-z0-9\\[\\]]"` in the regex (and any other symbols you want) - and for the `CharMatcher` you can `or` it with `CharMatcher.inRange('A', 'Z')`.

Problem

I am trying to write java code which would remove all unwanted characters and let there be only whitelisted ones. Example: ``` String[] whitelist = {"a", "b", "c"..."z", "0"..."9", "[", "]",...} ``` I want there only letters (lower and uppercase) and numbers + some next characters I would add. Then I would start `for()` cycle for every character in the string, and replace it with empty string if it isn't on whitelist. But that isn't good solution. Maybe it could be done somehow using pattern (regex)? Thanks.

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