// to create address object, and pass the address to faculty
// Must connect to other classes simultaneously
import java.util.ArrayList;
import javax.swing.JOptionPane;
public class Driver {
public static ArrayList<Student> student = new ArrayList<Student>();
public static ArrayList<Course> course = new ArrayList<Course>();
public static ArrayList<FacultyMember> faculty = new ArrayList<FacultyMember>();
public static void main(String[] args) {
String[] choices = { "0 Exit", "1 Add Student", "2 List of Students",
"3 Remove Student", "4 Create course", "5 List of Courses",
"6 Remove Course", "7 add instructor", "8 List of Instructors",
"9 Remove Instructor" };
student.add(new Student(308765433, "phillip", 2436, "Daly Street",
"Los Angeles", "CA", "USA"));
student.add(new Student(308765434, "Wilson Lucey", 2436,
"Broadway Street", "Los Angeles", "CA", "USA"));
student.add(new Student(308765432, "William", 2436,
"University Street", "Los Angeles", "CA", "USA"));
course.add(new Course(23545, "CS201"));
course.add(new Course(23546, "CS202"));
course.add(new Course(23547, "CS203"));
faculty.add(new FacultyMember(23477, "John"));
// faculty.add(new FacultyMember(23587, "Keenan"));
// faculty.add(new FacultyMember(236, "Parviz"));
int a = -1;
while (a < 0) {
int choice = JOptionPane.showOptionDialog(null, "Welcome", "Menu",
a, a, null, choices, a);
if (choice == 0) {
System.exit(0);
}
if (choice == 1) { // DONE
addStudent();
}
if (choice == 2) { // List all students inside array of students.
String a1 = "";
for (Student b : student) {
// b.toString();
a1 = a1 + b.toString() + "\n";
}
JOptionPane.showMessageDialog(null, a1);
}
if (choice == 3) {
removeStudent();
}
if (choice == 4) { // Show all courses inside array of courses
addCourse();
}
if (choice == 5) { // List of Course
String c1 = "";
for (Course b : course) {
// b.toString();
c1 = c1 + b.toString() + "\n";
}
JOptionPane.showMessageDialog(null, c1);
}
if (choice == 6) {
removeCourse();
}
if (choice == 7) {
addFaculty();
}
if (choice == 8) { // LIST OF FACULTY
String d1 = "";
for (FacultyMember d : faculty) {
// b.toString();
d1 = d1 + d.toString() + "\n";
}
JOptionPane.showMessageDialog(null, d1);
}
if (choice == 9) { // REMOVE FACULTY
removeFaculty();
}
}
}
private static void addStudent() {
int CIN = Integer.parseInt(JOptionPane.showInputDialog("Enter CIN: "));
String Name = JOptionPane.showInputDialog("Enter name");
// int street, String name, String city, String state, String country
int Street = Integer.parseInt(JOptionPane
.showInputDialog("Enter street #"));
String StreetName = JOptionPane.showInputDialog("Enter Street Name");
String City = JOptionPane.showInputDialog("Enter city");
String State = JOptionPane.showInputDialog("Enter state");
String Country = JOptionPane.showInputDialog("Enter country");
Student s1 = new Student(CIN, Name, Street, StreetName, City, State,
Country);
student.add(s1);
}
private static void addCourse() { // If
int courseID = Integer.parseInt(JOptionPane
.showInputDialog("Enter the id numer please!"));
String courseTitle = JOptionPane
.showInputDialog("Enter a course please!");
// String instructorName = JOptionPane
// .showInputDialog("Enter instructor for the course please!");
Course c1 = new Course(courseID, courseTitle); // CREATE OBJECT
course.add(c1);
}
// private static void Course(int courseID, String courseTitle, String term,
// String instructorName) {
//
// }
private static void addFaculty() {
int employeeID = Integer.parseInt(JOptionPane
.showInputDialog("Enter the employee id numer please!"));
String facultyName = JOptionPane
.showInputDialog("Enter the name of faculty please!"); // SAME
// AS
// STUDENTS
FacultyMember f1 = new FacultyMember(employeeID, facultyName);
faculty.add(f1);
}
public static void removeStudent() {
String a1 = "";
int i = 0;
for (Student b : student) {
// b.toString();
a1 = a1 + i++ + b.toString() + "\n";
}
int LineNumber = Integer.parseInt(JOptionPane.showInputDialog(null, a1
+ "Enter a row # to remove, please"));
student.remove(LineNumber);
for (int k = 0; k < student.size(); k++) {
System.out.println(student.get(k));
}
}
public static void removeCourse() {
String a1 = "";
int i = 0;
for (Course b : course) {
// b.toString();
a1 = a1 + i++ + b.toString() + "\n";
}
int LineNumber = Integer.parseInt(JOptionPane.showInputDialog(null, a1
+ "Enter a row # to remove, please"));
course.remove(LineNumber);
for (int k = 0; k < course.size(); k++) {
System.out.println(course.get(k));
}
}
public static void removeFaculty() {
String b1 = "";
int i = 0;
for (FacultyMember b : faculty) {
// b.toString();
b1 = b1 + i++ + b.toString() + "\n";
}
// JOptionPane.showMessageDialog(null,
// a1+"Enter a row # to remove, please");
//
int LineNumber = Integer.parseInt(JOptionPane.showInputDialog(null, b1
+ "Enter a row # to remove, please"));
faculty.remove(LineNumber);
for (int k = 0; k < faculty.size(); k++) {
System.out.println(faculty.get(k));
}
}
}
// }
public class Address {
/*
* An address has a street number, street name, city, state or province, and
* country.
*/
private int street;
private String name;
private String city;
private String state;
private String country;
public Address(int street, String name, String city, String state, String country) {
this.street = street;
this.name = name;
this.city= city;
this.state = state;
this.country = country;
}
public int getStreet() {
return street;
}
public void setStreet(int street) {
this.street = street;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCity(String city){
return city;
}
public void setCity(String city){
this.city=city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public String toString() {
return name + " "+
"Street: "+street+ " "+
"City: "+city+ " , "+ " State: "+ state +
"Country: "+country;
}
}
public class Person {
/*
* A Person has a name and an Address (represented by an object of class
* Address, not a String). Note that the subclasses of Person inherit the
* fields and methods of Person. You may need to override some of the
* methods in the subclasses.
*/
protected String name;
protected Address address;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public void setAddress(int street, String name, String city, String state,
String country) {
Address set1 = new Address(street, name, city, state, country);
this.address = set1;
}
public String toString() {
return "Name: " + name + " "+"Address: " + address.toString();
}
}
public class Course {
private int identifier;
private String courseTitle;
public Course(int identifier, String courseTitle){
this.identifier= identifier;
this.courseTitle= courseTitle;
}
public int getIdentifier() {
return identifier;
}
public String getCourseTitle() {
return courseTitle;
}
public String toString(){
return "Course ID: "+identifier + "Course title: "+ courseTitle;
}
public boolean contains(Course course) {
// TODO Auto-generated method stub
return false;
}
//setter to change the object values
//getters is to return some values we need
}
import java.util.ArrayList;
import java.util.List;
public class FacultyMember extends Person{
private int employeeID;
public ArrayList<Course>course = new ArrayList<Course>();
public FacultyMember(int employeeID, String nameIn){
this.name= nameIn;
this.employeeID = employeeID;
}
public int getID(){
return employeeID;
}
public void setID(int employeeID){
this.employeeID = employeeID;
}
public String getName(){
return name;
}
public void setName(String name){
this.name=name;
}
public List<Course> getCourse(){
return course;
}
public void addCourse(Course course) {
this.course.add(course);
}
public String toString(){
return "EmployeeID: " + employeeID +super.toString() ;
}
}
编写一个维护学生，课程和学习列表的驱动程序类 FacultyMembers并提供一个菜单，提供列出，创建和删除的方法 它们基于用户输入。驱动程序类也应该为a提供一种方法 学生添加和删除现有课程以及指派教师的方法 教授现有课程。当学生添加或时，不要创建新课程 当一名教师被指派教学时;让用户从中选择一个课程 列表。想一想在开始编码之前如何组织这个输入。
包含一个可以从main调用的方法，该方法将使用您的方法 添加和删除一些硬编码的测试数据（几个学生，几个教师 成员和几门课程。）这将让你编写列表并测试 不使用用户输入函数添加和删除项目的方法。
我的教师会员课程遇到困难我收到此错误
Exception in thread "main" java.lang.NullPointerException
at Person.toString(Person.java:30)
at FacultyMember.toString(FacultyMember.java:33)
at Driver.main(Driver.java:83)
答案 0 :(得分：0)
如前所述，您在Person类的地址实例变量上调用toString，但是您从未实例化该变量，这意味着它具有Object的默认值：null。
如果您尝试调用非实例化变量的成员，它将抛出NullPointerException。
public String toString() {
return "Name: " + name + " "+"Address: " + address.toString();
}
删除地址的toString调用，或确保实例化它。
话虽如此，您的代码还有很多可以改进的地方：
像这样的代码：if (choice == 6) {
removeCourse();
}
if (choice == 7) {
addFaculty();
}
if (choice == 8) { // LIST OF FACULTY
String d1 = "";
for (FacultyMember d : faculty) {
// b.toString();
d1 = d1 + d.toString() + "\n";
}
JOptionPane.showMessageDialog(null, d1);
}
if (choice == 9) { // REMOVE FACULTY
removeFaculty();
}
效率不高。我想我们都同意，如果选择== 6，选择永远不会（同时）具有值7,8或9，但你仍然会测试它们。
改善这种情况的一种方法是使用else语句：
if (choice == 6) {
removeCourse();
}else if (choice == 7) {
addFaculty();
} else if (choice == 8) { // LIST OF FACULTY
String d1 = "";
for (FacultyMember d : faculty) {
// b.toString();
d1 = d1 + d.toString() + "\n";
}
JOptionPane.showMessageDialog(null, d1);
}else if (choice == 9) { // REMOVE FACULTY
removeFaculty();
}
当你这样做时，它不会检查choice是否有其中一个值，如果它已经找到了它在之前测试中的值。因此，如果选择== 6，则不会测试7,8或9。
即使这样做好多了，但仍然不是很容易阅读。 switch语句可以在这里提供帮助：
switch(choice){
case 6: removeCourse();
break;
case 7: addFaculty();
break;
case 8: String d1 = "";
for (FacultyMember d : faculty) {
// b.toString();
d1 = d1 + d.toString() + "\n";}
JOptionPane.showMessageDialog(null, d1);
break;
case 9: removeFaculty();
break;
}
为此添加适当的缩进，您将更容易维护代码。
毫无疑问，你可以改进更多，但这会给你一些开始。