When running, below programme cannot reach the end of the main function..
I am new to JAVA, and cannot find its defections.. I need your help. Thanks.
import java.util.*;
class Schedule {
public String day;
private int startTime, endTime;
public Schedule(String input_day, int input_start, int input_end) {
    day = input_day;
    startTime = input_start;
    endTime = input_end;
}
/* clashWith: to check whether this schedule clash with a Schedule called otherSchedule
 *      PRE-Condition  : input must be of Schedule type
 *      POST-Condition : return true if two Schedule clash, return false if not.
 */
public boolean clashWith(Schedule otherSchedule) { 
    if(this.day != otherSchedule.day || this.endTime <= otherSchedule.startTime || this.startTime >= otherSchedule.endTime)
        return false;
    return true;
}
}
class Module {
String code;
Schedule lecture, tutorial, lab;
public Module(String input_code, Schedule input_lecture, Schedule input_tutorial, Schedule input_lab) {
    code = input_code;
    lecture = input_lecture;
    tutorial = input_tutorial;
    lab = input_lab;
}
/* count: to count number of classes(lecture, tutorial, and lab of only this Module) on day.
 *        For example: when day = "Monday", lecture is on Monday, tutorial is on Monday
 *        but lab is on Tuesday, then return 2. (lecture and tutorial are on Monday).
 *      PRE-Condition  :
 *      POST-Condition :
 */
public int count(String day) {
    int num = 0;
    if(lecture.day == day)
        num++;
    if(tutorial.day == day)
        num++;
    if(lab.day == day)
        num++;
    return num;
}
/* clashWith: to check whether this module clash with a Module called otherModule
 *      PRE-Condition  :
 *      POST-Condition :
 */
public boolean clashWith(Module otherModule) {
    if(lecture.clashWith(otherModule.lecture) || lecture.clashWith(otherModule.tutorial) || lecture.clashWith(otherModule.lab) )
        return true;
    if(tutorial.clashWith(otherModule.lecture) || tutorial.clashWith(otherModule.tutorial) || tutorial.clashWith(otherModule.lab))
        return true;
    if(lab.clashWith(otherModule.lecture) || lab.clashWith(otherModule.tutorial) || lab.clashWith(otherModule.lab))
        return true;
    return false;
}
}
class Timetable {
Vector<Module> listOfModule;
public Timetable() {
}
/* checkClash: to check whether otherModule clash with one of 
 *             the modules in our timetable list.
 *      PRE-Condition  :
 *      POST-Condition :
 */
public boolean checkClash(Module otherModule) {
    for(Module c: listOfModule)
        if(c.clashWith(otherModule))
            return true;
    return false;
}
/* add: to add a new module to the timetable list.
 *      PRE-Condition  :
 *      POST-Condition :
 */
public void add(Module module) {
    listOfModule.add(module);
}
/* count: to count number of classes on day.
 *      PRE-Condition  :
 *      POST-Condition :
 */
public int count(String day) {
    int count_day=0;
    for(Module c: listOfModule)
        count_day += c.count(day);
    return count_day;
}
}
public class Main {
public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    int num_operation;
    String code ;
    Timetable userTimetable = new Timetable();
    num_operation = input.nextInt();
    for(int i=0;i<num_operation;i++) {
        if(input.next() == "MODULE") {
            code = input.next();
            String day;
            int start, end;
            Schedule getLecSche = new Schedule(input.next(),input.nextInt(),input.nextInt());
            Schedule getTutSche = new Schedule(input.next(),input.nextInt(),input.nextInt());
            Schedule getLabSche = new Schedule(input.next(),input.nextInt(),input.nextInt());
            Module userModule = new Module(code, getLecSche, getTutSche, getLabSche);
System.out.println("Reached line 162");
            if(!userTimetable.checkClash(userModule)) {
                userTimetable.add(userModule);
                System.out.println("Added");
            }
            else
                System.out.println("Clashed");
        }
        else if(input.next() == "COUNT"){
            code = input.next();
            System.out.println(userTimetable.count(code));
        }
    }
}
}