CompareExample.java

import java.util.Date;
import java.util.Arrays;
import java.util.List;
import java.util.Collections;
import java.util.Comparator;
import java.text.SimpleDateFormat;
import java.text.ParseException;

class Employee { 
    String name;
    String hireDate;
    String hireHour; 
    static Employee hired( String name ,  String date, String hour ) { 
        Employee e = new Employee();
        e.name = name;
        e.hireDate = date;
        e.hireHour = hour;
        return e;
    }
    public String toString() { 
        return String.format("name: %s, hire: %s %s%n", name, hireDate, hireHour );
    }
}
class CompareExample {
    public static void main( String ... args )  { 
        List<Employee> list = Arrays.asList( 
                Employee.hired( "A", "01/01/2000" , "08:00" ),
                Employee.hired( "B","01/01/2000" , "16:00" ),
                Employee.hired( "C","01/01/1999" , "00:00" ),
                Employee.hired( "D","24/02/2013" , "15:32" ),
                Employee.hired( "E","08/07/2011" , "17:09" ),
                Employee.hired( "F","08/07/2011" , "17:09" )
            );
        Collections.sort( list, new Comparator<Employee>() { 
            public int compare( Employee a, Employee b ) { 
                try { 
                    int result = toDate( a.hireDate ).compareTo( toDate( b.hireDate ));
                    return result != 0 ? result : toDate(a.hireHour).compareTo( toDate( b.hireHour));
                } catch ( ParseException e ) { 
                    throw new RuntimeException( e );
                }
            }
        });
        System.out.println( list ); 
    }
    static SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy hh:mm");
    private static Date toDate( String string ) throws ParseException { 
        return sdf.parse(string.length() == 10 ? string + " 00:00" : "01/01/1970 " + string); 
    }
}

// output
$ java CompareExample
[name: C, hire: 01/01/1999 00:00
, name: A, hire: 01/01/2000 08:00
, name: B, hire: 01/01/2000 16:00
, name: E, hire: 08/07/2011 17:09
, name: F, hire: 08/07/2011 17:09
, name: D, hire: 24/02/2013 15:32
]