java is digit
The java.lang.Character.isDigit(char ch) is an inbuilt method in java
which determines whether a specified character is a digit or not.
   // two characters
        char c1 = 'A', c2 = '4';
  
        // Function to check if the character
        // is digit or not
        System.out.println(
            c1 + " is a digit -> "
            + Character.isDigit(c1));
        System.out.println(
            c2 + " is a digit -> "
            + Character.isDigit(c2));
