Android Java - String .replaceAll to replace specific characters (regex)

Question

I need to remove some specific "special" characters and replace them with empty string if they show up. I am currently having a problem with the regex, probably with the Java escaping. I can't put them all together, it just doesn't work, I tried a lot! T_T

Currently I am doing it one by one which is kinda silly, but for now at least it works, like that :

public static String filterSpecialCharacters(String string) {
    string = string.replaceAll("-", "");
    string = string.replaceAll("\\[", "");
    string = string.replaceAll("\\]", "");
    string = string.replaceAll("\\^", "");
    string = string.replaceAll("/", "");
    string = string.replaceAll(",", "");
    string = string.replaceAll("'", "");
    string = string.replaceAll("\\*", "");
    string = string.replaceAll(":", "");
    string = string.replaceAll("\\.", "");
    string = string.replaceAll("!", "");
    string = string.replaceAll(">", "");
    string = string.replaceAll("<", "");
    string = string.replaceAll("~", "");
    string = string.replaceAll("@", "");
    string = string.replaceAll("#", "");
    string = string.replaceAll("$", "");
    string = string.replaceAll("%", "");
    string = string.replaceAll("\\+", "");
    string = string.replaceAll("=", "");
    string = string.replaceAll("\\?", "");
    string = string.replaceAll("|", "");
    string = string.replaceAll("\"", "");
    string = string.replaceAll("\\\\", "");
    string = string.replaceAll("\\)", "");
    string = string.replaceAll("\\(", "");
    return string;
}

Those are all the character I need to remove:

- [ ] ^ / , ' * : . ! > < ~ @ # $ % + = ? | " \ ) (

I am clearly missing something, I can't figure out how to put it all in one line. Help?

It looks very much like string = string.replaceAll("\\p{Punct}+", ""). See Java regex reference: \p{Punct} Punctuation: One of !"#$%&'()*+,-./:;<=>?@[]^_`{|}~. However, I see you have a bit fewer symbols defined in your class. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 9, 2017 at 7:32

Wiktor Stribiżew · Accepted Answer · 2016-03-20 11:01:17Z

11

Your code does not work in fact because .replaceAll("$", "") replaces an end of string with empty string. To replace a literal $, you need to escape it. Same issue is with the pipe symbol removal.

All you need to do is to put the characters you need to replace into a character class and apply the + quantifier for better performance, like this:

string = string.replaceAll("[-\\[\\]^/,'*:.!><~@#$%+=?|\"\\\\()]+", "");

Note that inside a character class, most "special regex metacharacters" lose their special status, you only have to escape [, ], \, a hyphen (if it is not at the start/end of the character class), and a ^ (if it is the first symbol in the "positive" character class).

DEMO:

String s = "-[]^/,'*:.!><~@#$%+=?|\"\\()TEXT";
s = s.replaceAll("[-\\[\\]^/,'*:.!><~@#$%+=?|\"\\\\()]+", "");
System.out.println(s); // => TEXT

edited Mar 20, 2016 at 11:01

answered Mar 20, 2016 at 10:52

Wiktor Stribiżew

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4 Comments

Alan Moore Over a year ago

The pipe (|) also needed escaping in his original code (but not in yours).

Wiktor Stribiżew Over a year ago

Yes, added a note on that to the answer.

Alan Moore Over a year ago

I meant to say he should have escaped it, but didn't.

Wiktor Stribiżew Over a year ago

It looks very much like string = string.replaceAll("\\p{Punct}+", ""). See Java regex reference: \p{Punct} Punctuation: One of !"#$%&'()*+,-./:;<=>?@[]^_`{|}~. However, I see you have a bit fewer symbols defined in your class.

Shree Krishna · Accepted Answer · 2016-03-20 11:03:14Z

6

Use these codes

String REGEX = "YOUR_REGEX";
Pattern p = Pattern.compile(REGEX);
Matcher m = p.matcher(yourString);
yourString = m.replaceAll("");

UPDATE :

Your REGEX looks something like

String REGEX = "-|\\[|\\]|\\^|\\/|,|'|\\*|\\:|\\.|!|>|<|\\~|@|#|\\$|%|\\+|=\\?|\\||\\\\|\\\\\\\\|\\)|\\(";

SAPMLE :

String yourString = "#My (name) -is @someth\ing"";
//Use Above codes
Log.d("yourString",yourString);

OUTPUT

edited Mar 20, 2016 at 11:03

answered Mar 20, 2016 at 10:10

Shree Krishna

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8 Comments

Maroun Over a year ago

How does this answer the question?

JozeRi Over a year ago

first of all thank you for taking your time and trying to help me. appreciate it a lot ! 2ndly, -> String REGEX = "\"[^/,'*:<>!~@#$%^&()+=?()\\\"|!\[#$-]+\""; Pattern p = Pattern.compile(REGEX); Matcher m = p.matcher(string); string = m.replaceAll(""); - this doesn't work.

Shree Krishna Over a year ago

can you post your current string.

Shree Krishna Over a year ago

Are you sure that you are using valid regex?

JozeRi Over a year ago

@ShreeKrishna I did found this helpful! it's certainly another good way to achieve my desired goal, thanks a lot for your time in providing an answer! appreciate it a lot.

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