How to match a fixed set of characters using Java RegEx

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