Java：创建一个简单类，并测试其方法（第四周）

蔚落 2022-05-28 10:59 82阅读 0赞

题目来源：大工慕课 [链接][Link 1]  
作者：Caleb Sung

## 题目要求 ##

1.  阅读Core Java中的示例代码清单4.2。
2.  实现一学生类，其Fields包括身份证，姓名，性别，年龄，专业，GPA以及学生已经注册的课程列表。 另外，方法还包括分别获取所有子类的姓名以及已注册课程的行为。
3.  在主函数中，创建如下所示的学生数组，然后测试Student类的所有方法。

<table> 
 <thead> 
  <tr> 
   <th>ID</th> 
   <th>Name</th> 
   <th>Gender</th> 
   <th>Age</th> 
   <th>Major</th> 
   <th>Courses</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>150001</td> 
   <td>HanMei</td> 
   <td>F</td> 
   <td>19</td> 
   <td>E-Commerce</td> 
   <td>DB, Java, Econmics</td> 
  </tr> 
  <tr> 
   <td>150002</td> 
   <td>LiLei</td> 
   <td>M</td> 
   <td>20</td> 
   <td>E-Commerce</td> 
   <td>DB, Java, Data Structures</td> 
  </tr> 
  <tr> 
   <td>150003</td> 
   <td>Tom</td> 
   <td>M</td> 
   <td>19</td> 
   <td>Bioinformatics</td> 
   <td>Java, Data Structures, Biology</td> 
  </tr> 
  <tr> 
   <td>150004</td> 
   <td>Jerry</td> 
   <td>M</td> 
   <td>18</td> 
   <td>Bioinformatics</td> 
   <td>DB, Java, Data Structures</td> 
  </tr> 
 </tbody> 
</table>

## 解答示范 ##

public class StudentTest { 
    
        public static void main(String[] args) {
            //Database initialization;
            Student[] stu = new Student[4]; 
            stu[0] = new Student(150001, "Hanmei", 'F', 19, 3, "E-Commerce", 3.3);
            stu[1] = new Student(150002, "LiLei", 'M', 20, 3, "E-Commerce", 3.5);
            stu[2] = new Student(150003, "Tom", 'M', 19, 3, "Bioinformatics", 3.4);
            stu[3] = new Student(150004, "Jerry", 'M', 18, 3, "Bioinformatics", 3.2);
    
            stu[0].enroll("DB");
            stu[0].enroll("Java");
            stu[0].enroll("Econmics");
            stu[1].enroll("DB");
            stu[1].enroll("Java");
            stu[1].enroll("Data Structures");
            stu[2].enroll("Java");
            stu[2].enroll("Data Structures");
            stu[2].enroll("Biology");
            stu[3].enroll("DB");
            stu[3].enroll("Java");
            stu[3].enroll("Data Structures");
    
            //Output
            for(int i = 0; i <= 3; i++) {
                System.out.println(stu[i].getName()+" (ID: "+stu[i].getId()+") :");
                //System.out.println("Gender: "+stu[i].getGender());
                //System.out.println("Age: "+stu[i].getAge());
                //System.out.println("Major: "+stu[i].getMajor());
                //System.out.println("GPA: "+stu[i].getGpa());
                System.out.println("Courses:");
                for (String c : stu[i].getCourses())
                    System.out.println("@ "+c);
                System.out.println("---------------------------------");
            }System.out.println("Finished.");
            System.out.println("---------------------------------\n");
    
            //Add course
            System.out.println("Do you want to add courses to students? (Y/N)");
            Scanner in = new Scanner(System.in);
            char sym = in.next().charAt(0);
            if (sym == 'Y') {
                System.out.println("Please input a student's id(the student must be in the list:");
                Scanner inp = new Scanner(System.in);
                String tmp = inp.nextLine();
                for(int i = 0; i <= 3; i++) {
                    String name = stu[i].getName();
                    if(name == tmp) {
                        in = new Scanner(System.in);
                        String cor = in.nextLine();
                        stu[i].enroll(cor);
                        if(stu[i].enroll(cor) == true) {
                            System.out.println("Successfully enrolled.");
                            break;
                        }else {
                            System.out.println("Failed in enrolling");
                            break;
                        }
                    }System.out.println("Cannot enroll more courses!");
                }inp.close();
            }
            else if (sym == 'N')
                System.out.println("Thanks for using! :)");
            else
                System.out.println("Illegal Command!");
            in.close();
        }
    
        public static class Student{ 
            // fields
            private long id;
            private String name;
            private char gender;
            private int age;
            private String major;
            private double gpa;
            private String[] courses;
    
            // constructors
            public Student(long id, String name, char gender, int age, int maxCourses, String major, double gpa) {
                this.id = id;
                this.name = name;
                this.gender = gender;
                this.age = age;
                this.major = major;
                this.gpa = gpa;
                //this.courses = courses;
                courses = new String[maxCourses];
            }
    
            //methods
            public long getId() {
                return id;
            }
    
            public String getName() {
                return name;
            }
    
            public char getGender() {
                return gender;
            }
    
            public int getAge() {
                return age;
            }
    
            public String getMajor() {
                return major;
            }
    
            public double getGpa() {
                return gpa;
            }
    
            public String[] getCourses() {
                return courses;
            }
    
            boolean enroll(String course) {
                for (int i = 0; i < this.courses.length; ++i) {
                    if (courses[i] == null) {
                        courses[i] = course;
                        return true;
                    }
                }return false;
            }
        }
    }

[Link 1]: https://mooc.dlut.edu.cn/