How to check if a character is a special character in java

• To check if string contains special character or not or  check whether first character is special character or not we can use regex or contains method of sting class.
• By using  java.util.regex.Matcher class and java.util.regex.Pattern class methods we can check whether string has special character or not
• Lets see an example program on how to check a string has special character or not using java regex.

Program #1: Java example program to check string has special character or not using  java regex's?
 

1. package StringInterviewprograms;
2. import java.util.regex.Matcher;
3. import java.util.regex.Pattern;
4.  
5. public class CheckSpecialCharacterString {
6.  
7.     /**
8.      * Check whether the String contains special character or not using java
9.      * @author www.instanceofjava.com
10.      */
11.     
12. public static void main(String[] args) {
13.  
14. String Str="Java String interview questions ";
15. String Str1="Java String interview questions % ";
16. Pattern p = Pattern.compile("[^a-z0-9 ]", Pattern.CASE_INSENSITIVE);
17. Matcher m = p.matcher(Str);
18. boolean check = m.find();
19.  
20. if (check)
21.    System.out.println("String: "+Str+" contains special character");
22. else
23.    System.out.println("String: "+Str+" does not contains any special character");
24.  
25. Matcher m1= p.matcher(Str1);
26.  
27. boolean flag = m1.find();
28.  
29. if(flag)
30.        System.out.println("String: "+Str1+" contains special character");
31.     else
32.        System.out.println("String: "+Str1+" does not contains any special character");
33.  
34.    }
35. }

Output:

1. String: Java String interview questions  does not contains any special character
2. String: Java String interview questions %  contains special character

• We can check each character of a string is special character or not without using java regex's.
• By using String class contains method and for loop we can check each character of a sting is special character or not.
• Let us see a java example program on how to check each character (including space) of a string is special character or not.
• String validation for special characters.

Program #2: Java example program to check each character of string is special character or not without using  java regex's?

1. package StringInterviewprograms;
2.  
3. import java.util.regex.Matcher;
4. import java.util.regex.Pattern;
5.  
6. public class CheckSpecialCharacterString {
7.  
8.     /**
9.      * Check whether the each character of String is special character or not using java
10.      * @author www.instanceofjava.com
11.      */
12.     
13. public static void main(String[] args) {
14. String Str="Java String interview questions*$%";
15.   
16. String specialCharacters=" !#$%&'()*+,-./:;<=>?@[]^_`{|}";
17.  
18. for (int i = 0; i < Str.length(); i++) {
19.     
20.     if (specialCharacters.contains(Character.toString(Str.charAt(i))))
21.     {
22.        
23.         System.out.println(Str.charAt(i)+": is a special character");
24.     }  
25.   }
26.  
27. }
28.  
29. }

Output:

1.  : is a special character
2.  : is a special character
3.  : is a special character
4. *: is a special character
5. $: is a special character
6. %: is a special character

Program #3: Java example program to check each character of string is special character or not without using  java regex's Using Eclipse IDE.