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
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