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I want to create a program for checking whether any inputted character is a special character or not. The problem is that I hava no idea what to do: either check for special characters or check for the ASCII value. Can anyone tell me if I can just check for the numerical ASCII value using 'if' statement or if I need to check each special character?

Anon the Rocker Beginner
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  • if only there was an expression you could use on a regular basis to do that... hmmm its a shame really – SaggingRufus Mar 23 '17 at 18:12
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    special character as in... not [a-zA-Z0-9] ? – Wietlol Mar 23 '17 at 18:14
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    Could you clarify your question? Maybe give us some example and clarify what you mean by *special*. – Pshemo Mar 23 '17 at 18:15
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    Possible duplicate of [JAVA: check a string if there is a special character in it](http://stackoverflow.com/questions/1795402/java-check-a-string-if-there-is-a-special-character-in-it) – Benjamin Diaz Mar 23 '17 at 18:16

3 Answers3

5

You can use regex (Regular Expressions):

if (String.valueOf(character).matches("[^a-zA-Z0-9]")) {
    //Your code
}

The code in the if statement will execute if the character is not alphanumeric. (whitespace will count as a special character.) If you don't want white space to count as a special character, change the string to "[^a-zA-Z0-9\\s]".

Further reading:

ostrichofevil
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    Maybe add a link to http://www.regex101.com ? its perfectly if you want to build a regular expression – Wietlol Mar 23 '17 at 18:30
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You can use isLetter(char c) and isDigit(char c). You could do it like this:

char c;
//assign c in some way
if(!Character.isLetter(c) && !Character.isDigit(c)) {
    //do something in case of special character
} else {
    //do something for non-special character
}

EDIT: As pointed out in the comments it may be more viable to use isLetterOrDigit(char c) instead.

EDIT2: As ostrichofevil pointed out (which I did not think or know of when i posted the answer) this solution won't restrict "non-special" characters to A-Z, a-z and 0-9, but will include anything that is considered a letter or number in Unicode. This probably makes ostrichofevil's answer a more practical solution in most cases.

Woopdidoo
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  • Note that `Character.isLetter` will return true for any Unicode character classified as a letter, not just the letters *a-z* and *A-Z*. The same goes for `isDigit`; there are other characters than *0-9* which are classified as digits. – ostrichofevil Mar 23 '17 at 18:27
  • use `!Character.isLetterOrDigit(c);` rather than using && operation. However code will return true for `$ _ ` and so on. – Sanjay Madnani Mar 23 '17 at 18:39
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you can achieve it in this way : 

char[] specialCh = {'!','@',']','#','$','%','^','&','*'}; // you can specify all special characters in this array

boolean hasSpecialChar = false;

char current;

for (Character c : specialCh) {
      if (current == c){
          hasSpecialChar = true;
      }
 }
Oghli
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