remove all special characters in java

Question

Possible Duplicate:
Replacing all non-alphanumeric characters with empty strings

import java.util.Scanner;
import java.util.regex.*;
public class io{
public static void main(String args[]){
Scanner scan = new Scanner(System.in);
String c;
if((c=scan.nextLine())!=null)
 {
Pattern pt = Pattern.compile("[^a-zA-Z0-9]");
Matcher match= pt.matcher(c);
    while(match.find()){
         c=c.replace(Character.toString(c.charAt(match.start())),"");
         }
    System.out.println(c);
      }
   }
}

Case 1

Input : hjdg$h&jk8^i0ssh6
Expect : hjdghjk8i0ssh6
Output : hjdgh&jk8^issh6

Case 2

Input : hjdgh&jk8i0ssh6
Expect : hjdghjk8i0ssh6
Output : hjdghjk8i0ssh6

Case 3

Input : hjdgh&j&k8i0ssh6
Expect : hjdghjk8i0ssh6
Output : hjdghjki0ssh6

Anyone please help me to figure out, what is wrong in my code logic ??

Consider looking at the Java naming conventions and format your source code before you submit the question. — rtheunissen, Jan 16 '13 at 15:15
@paranoid-android actually, i wrote the above code on notepad.. :( — Ravi, Jan 16 '13 at 15:16
That looks.. like a really complicated way of doing it. `String s = "hjdg$h&jk8^i0ssh6"; System.out.println(s.replaceAll("[^A-Za-z0-9]", "")` — Jens, Jan 16 '13 at 15:18
Just because it's in Notepad doesn't mean you can't indent with Tab. :p — rtheunissen, Jan 16 '13 at 15:21
@var___ No worries man, just being difficult. As long as your tried to that's fine. :) — rtheunissen, Jan 16 '13 at 15:31
If you want valid chars, like ç, à and ã use .replaceAll("[!@#$%ˆ&*/\$\$\\{\\};:<>/?,.|\\[\\]]", ""); — Ricardo Gellman, Jan 18 '19 at 12:45

score 25 · Accepted Answer · answered Jan 16 '13 at 15:18

25

use [\\W+] or "[^a-zA-Z0-9]" as regex to match any special characters and also use String.replaceAll(regex, String) to replace the spl charecter with an empty string. remember as the first arg of String.replaceAll is a regex you have to escape it with a backslash to treat em as a literal charcter.

          String c= "hjdg$h&jk8^i0ssh6";
        Pattern pt = Pattern.compile("[^a-zA-Z0-9]");
        Matcher match= pt.matcher(c);
        while(match.find())
        {
            String s= match.group();
        c=c.replaceAll("\\"+s, "");
        }
        System.out.println(c);

answered Jan 16 '13 at 15:18

PermGenError

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`c=c.replace(match.group(), "");` this one also working . Why ?? – Ravi Jan 16 '13 at 16:45
@var___ note that i used replaceAll which takes first args as regex, while you are using replace whihc doesn't take regex, thus it works .. :) – PermGenError Jan 16 '13 at 16:52
ok.. i got it now.. thanks !! – Ravi Jan 16 '13 at 16:53
1

same question, better answer: http://stackoverflow.com/a/4283366/637609 – Mark W Dec 13 '16 at 15:48
3

This also replaces all white spaces. So, will not be a good idea to apply it on a sentence. – Vini Jan 16 '17 at 12:18

score 17 · Answer 2 · edited Jan 20 '21 at 21:12

17

You can read the lines and replace all special characters safely this way.
Keep in mind that if you use \\W you will not replace underscores.

Scanner scan = new Scanner(System.in);

while(scan.hasNextLine()){
    System.out.println(scan.nextLine().replaceAll("[^a-zA-Z0-9]", ""));
}

edited Jan 20 '21 at 21:12

Naveen Kumar Alone

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answered Jan 16 '13 at 15:17

rtheunissen

7,347
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what if i want to use `regex` package. – Ravi Jan 16 '13 at 15:24
Well if it's for an assignment and you HAVE to use `regex` package, then you may be looking at an unnecessarily complex solution. Why do you want to use the `regex` package? – rtheunissen Jan 16 '13 at 15:28
So, that i can learn more about `regex` package – Ravi Jan 16 '13 at 15:31
In that case `GanGnaMStYleOverFlowErroR`'s answer is probably the best? – rtheunissen Jan 16 '13 at 15:35

score 7 · Answer 3 · answered Jan 16 '13 at 15:21

Your problem is that the indices returned by match.start() correspond to the position of the character as it appeared in the original string when you matched it; however, as you rewrite the string c every time, these indices become incorrect.

The best approach to solve this is to use replaceAll, for example:

        System.out.println(c.replaceAll("[^a-zA-Z0-9]", ""));

remove all special characters in java

3 Answers3

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