Character class: Negation - Java regular expressions


The character classes in Java regular expression is defined using the square brackets "[ ]", this subexpression matches a single character from the specified or, set of possible characters.

For example the regular expression [abc] matches a single character a or, b or, c. Similarly, "[a-z]" matches a single character from a to z.

Similarly, the negation variant of the character class is defined as "[^ ]" (with ^ within the square braces), it matches a single character which is not in the specified or set of possible characters.

For example the regular expression [^abc] matches a single character except a or, b or, c. Similarly, "[^a-z]" matches a character excepts alphabets from a to z.

Example 1

 Live Demo

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexExample1 {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter input text: ");
      String input = sc.nextLine();
      String regex = "[^aeiou]";
      //Creating a pattern object
      Pattern pattern = Pattern.compile(regex);
      //Matching the compiled pattern in the String
      Matcher matcher = pattern.matcher(input);
      int count =0;
      while (matcher.find()) {
         count++;
      }
      System.out.println("Number of non-vowel characters : "+count);
   }
}

Output

Enter input text:
sample data
Number of non-vowel characters : 7
raja
Published on 13-Jan-2020 06:45:41
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