The character classes allow you to accept a single character from a fixed set of characters. For example,
The expression “[tmp]” matches the characters t or, m or, p.
The expression “[^tp]” matches the characters other than t or, p.
Example 1
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Example {
public static void main(String args[]) {
//Reading String from user
System.out.println("Enter a String");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
//Regular expression to match the characters t or, m or, p
String regex = "[tmp]";
//Compiling the regular expression
Pattern pattern = Pattern.compile(regex);
//Retrieving the matcher object
Matcher matcher = pattern.matcher(input);
int count = 0;
while(matcher.find()) {
count++;
}
System.out.println("Occurrences: "+count);
}
}Output
Enter a String hello how are you welcome to tutorialspoint Occurrences :6
Example 2
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Example {
public static void main(String args[]) {
//Reading String from user
System.out.println("Enter a String");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
String regex = "[^abcdef]";
//Compiling the regular expression
Pattern pattern = Pattern.compile(regex);
//Retrieving the matcher object
Matcher matcher = pattern.matcher(input);
int count = 0;
while(matcher.find()) {
count++;
}
System.out.println("Occurrences :"+count);
}
}Output
Enter a String Hello how are you welcome to tutorialspoint Occurrences :36