24 Hour format time validation using regular expressions

This asset basically make use of regular expressions to validate against the 24 hour time format . It restricts the user to enter the time other than 24 hour format .
The code shown below uses pattern matcher to match the regular expression with the input.

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Time24HoursValidator{

   private Pattern pattern;
   private Matcher matcher;

   private static final String TIME24HOURS_PATTERN = 
                       " (([0-1]?[0-9])|(2[0-3])):[0-5][0-9] ";   
                  
   public Time24HoursValidator(){
    pattern = Pattern.compile(TIME24HOURS_PATTERN);
   }
 
   /**
    * Validate time in 24 hours format with regular expression
    * @param time time address for validation
    * @return true valid time fromat, false invalid time format
    */
   public boolean validate(final String time){

    matcher = pattern.matcher(time);
    return matcher.matches();

   }
}