Replace Unicode Control Characters

Question

I need to replace all special control character in a string in Java.

I want to ask the Google maps API v3, and Google doesn\'t seems to like these characters.

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Answer 1

If you want to delete all characters in Other/Control Unicode category, you can do something like this:

    System.out.println(
        "a\u0000b\u0007c\u008fd".replaceAll("\\p{Cc}", "")
    ); // abcd

Note that this actually removes (among others) '\u008f' Unicode character from the string, not the escaped form "%8F" string.

If the blacklist is not nicely captured by one Unicode block/category, Java does have a powerful character class arithmetics featuring intersection, subtraction, etc that you can use. Alternatively you can also use a negated whitelist approach, i.e. instead of explicitly specifying what characters are illegal, you specify what are legal, and everything else then becomes illegal.

API links

• java.util.regex.Pattern
• regular-expressions.info/Character Class

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Examples

Here's a subtraction example:

    System.out.println(
        "regular expressions: now you have two problems!!"
            .replaceAll("[a-z&&[^aeiou]]", "_")
    );
    //   _e_u_a_ e___e__io__: _o_ _ou _a_e __o __o__e__!!

The […] is a character class. Something like [aeiou] matches one of any of the lowercase vowels. [^…] is a negated character class. [^aeiou] matches one of anything but the lowercase vowels.

[a-z&&[^aeiou]] matches [a-z] subtracted by [aeiou], i.e. all lowercase consonants.

The next example shows the negated whitelist approach:

    System.out.println(
        "regular expressions: now you have two problems!!"
            .replaceAll("[^a-z]", "_")
    );
    //   regular_expressions__now_you_have_two_problems__

Only lowercase letters a-z are legal; everything else is illegal.