Since Checkstyle 8.45
Checks that there is no whitespace before the colon in a switch block.
To configure the check:
<module name="Checker">
  <module name="TreeWalker">
    <module name="NoWhitespaceBeforeCaseDefaultColon"/>
  </module>
</module>
        Example:
class Example1 {
  void example() {
    switch(1) {
      case 1 : // violation '':' is preceded with whitespace'
        break;
      case 2:
        break;
      default : // violation '':' is preceded with whitespace'
        break;
    }
    switch(2) {
      case 2:
        break;
      case 3, 4
        : break; // violation '':' is preceded with whitespace'
      case 5,
        6: break;
      default
            : // violation '':' is preceded with whitespace'
        break;
    }
    switch(DayOfWeek.MONDAY) {
      case MONDAY, FRIDAY, SUNDAY: System.out.println("  6"); break;
      // violation below '':' is preceded with whitespace'
      case TUESDAY               : System.out.println("  7"); break;
    }
  }
}
        All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.
com.puppycrawl.tools.checkstyle.checks.whitespace