Đâu là lỗi sai của mình trong đoạn code này?

diagram.png682x511 91.9 KB

Trên là Diagram của bài đó

 package tuan05;

public class Faculty {
	private String facultyID;
	private String lastName;
	private String firstName;
	private String office;
	public Faculty(String facultyID, String lastName, String firstName, String office) {
		super();
		this.facultyID = facultyID;
		this.lastName = lastName;
		this.firstName = firstName;
		this.office = office;
	}
	
	public Faculty(){
		this("0","0","0","0");
	}

	public String getFacultyID() {
		return facultyID;
	}

	public void setFacultyID(String facultyID) {
		this.facultyID = facultyID;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getOffice() {
		return office;
	}

	public void setOffice(String office) {
		this.office = office;
	}

	@Override
	public String toString() {
		return String.format("%10s
%10s
%10s
%10s
",facultyID,lastName,firstName,office);
	}
}

Class

package tuan05;

public class Section{
	private String sectionNbr;
	private String semester;
	private String room;
	private static Faculty teacher;
	public Section(String sectionNbr, String semester, String room,Faculty teacher) {
		super();
		this.sectionNbr = sectionNbr;
		this.semester = semester;
		this.room = room;
		Section.teacher = teacher;
	}

	public Section(){
		this("0","0","0",teacher);
	}


	public String getSectionNbr() {
		return sectionNbr;
	}

	public void setSectionNbr(String sectionNbr) {
		this.sectionNbr = sectionNbr;
	}

	public String getSemester() {
		return semester;
	}

	public void setSemester(String semester) {
		this.semester = semester;
	}

	public String getRoom() {
		return room;
	}

	public void setRoom(String room) {
		this.room = room;
	}

	@Override
	public String toString() {
		return "Mã học phần: " + sectionNbr + "
Học kỳ: " + semester + "
Phòng học: "
				+ room + "
Giảng viên: " + teacher.getLastName() + " " + teacher.getFirstName()
				+ "(Khoa: " + teacher.getOffice() + ")";
	}
}

Class

package tuan05;

public class Course {
	private String courseNbr;
	private String courseTitle;
	private int credits;
	private Section[] sections;
	private int i=0;
	
	public Course(){
		this("0","0",0);
	}

	public Course(String courseNbr, String courseTitle, int credits) {
		super();
		this.courseNbr = courseNbr;
		this.courseTitle = courseTitle;
		this.credits = credits;
		sections = new Section[5];
	}

	public String getCourseNbr() {
		return courseNbr;
	}

	public void setCourseNbr(String courseNbr) {
		this.courseNbr = courseNbr;
	}

	public String getCourseTitle() {
		return courseTitle;
	}

	public void setCourseTitle(String courseTitle) {
		this.courseTitle = courseTitle;
	}

	public int getCredits() {
		return credits;
	}

	public void setCredits(int credits) {
		this.credits = credits;
	}
	
	public void addSection(String SectionNbr, String semester, String room, Faculty listFa){
		Section st = new Section(SectionNbr,semester,room,listFa);
		sections[i]=st;
		i++;
	}
	
	public void displayAll(){
		for(Section sec : sections){
			if(sec==null)
				break;
			System.out.println(sec + "
");
		}
	}

	@Override
	public String toString() {
		return "Khóa học: [" + courseNbr + " - " + courseTitle + " (" + credits + "TC)]
" ;
	}
}

Class

package tuan05;

public class Driver {
	public static void main(String[] args) {
		Faculty f1 = new Faculty("11111","Lê Kim","Khánh","CNTT");
		Faculty f2 = new Faculty("22222","Nguyễn Thành","Danh","CNTT");
		Course cs = new Course("THVP","Tin học văn phòng",4);
		System.out.println(cs);
		cs.addSection("120151","I - 2015", "H5.02",f1);
		System.out.println("=========================================");
		cs.addSection("220151","II - 2015", "B4.01",f2);
		cs.displayAll();
	}
}

test.png803x755 28.4 KB

Mình có thử chuyển Faculty sang kiểu mảng nhưng mà chuyển xong thì tè le đủ kiểu lại còn chạy không được >_<