Bài tập tự luận Java nâng cao có lời giải

2. Tạo lớp Student.java

package vn.eLib;
import java.io.Serializable;
/**
 * Student class
 *
 * @author eLib.vn
 */
public class Student implements Serializable {
  private int id;
  private String name;
  private byte age;
  private String address;
  /* điểm trung bình của sinh viên */
  private float gpa;
  public Student() {}
  public Student(int id, String name, byte age, String address, float gpa) {
    super();
    this.id = id;
    this.name = name;
    this.age = age;
    this.address = address;
    this.gpa = gpa;
  }
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public byte getAge() {
    return age;
  }
  public void setAge(byte age) {
    this.age = age;
  }
  public String getAddress() {
    return address;
  }
  public void setAddress(String address) {
    this.address = address;
  }
  public float getGpa() {
    return gpa;
  }
  public void setGpa(float gpa) {
    this.gpa = gpa;
  }
}

3. Tạo lớp StudentDao.java

package vn.eLib;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
/**
 * StudentManager class
 *
 * @author eLib.vn
 */
public class StudentManager {
  public static Scanner scanner = new Scanner(System. in );
  private List < Student > studentList;
  private StudentDao studentDao;
  /**
     * init StudentDao object and
     * read list student when init StudentManager object
     */
  public StudentManager() {
    studentDao = new StudentDao();
    studentList = studentDao.read();
  }
  /**
     * add student to studentList
     *
     * @param student
     */
  public void add() {
    int id = (studentList.size() > 0) ? (studentList.size() + 1) : 1;
    System.out.println("student id = " + id);
    String name = inputName();
    byte age = inputAge();
    String address = inputAddress();
    float gpa = inputGpa();
    Student student = new Student(id, name, age, address, gpa);
    studentList.add(student);
    studentDao.write(studentList);
  }
  /**
     * edit student by id
     *
     * @param id
     */
  public void edit(int id) {
    boolean isExisted = false;
    int size = studentList.size();
    for (int i = 0; i < size; i++) {
      if (studentList.get(i).getId() == id) {
        isExisted = true;
        studentList.get(i).setName(inputName());
        studentList.get(i).setAge(inputAge());
        studentList.get(i).setAddress(inputAddress());
        studentList.get(i).setGpa(inputGpa());
        break;
      }
    }
    if (!isExisted) {
      System.out.printf("id = %d not existed.\n", id);
    } else {
      studentDao.write(studentList);
    }
  }
  /**
     * delete student by id
     *
     * @param id: student id
     */
  public void delete(int id) {
    Student student = null;
    int size = studentList.size();
    for (int i = 0; i < size; i++) {
      if (studentList.get(i).getId() == id) {
        student = studentList.get(i);
        break;
      }
    }
    if (student != null) {
      studentList.remove(student);
      studentDao.write(studentList);
    } else {
      System.out.printf("id = %d not existed.\n", id);
    }
  }
  /**
     * sort student by name
     */
  public void sortStudentByName() {
    Collections.sort(studentList, new SortStudentByName());
  }
  /**
     * sort student by id
     */
  public void sortStudentByGPA() {
    Collections.sort(studentList, new SortStudentByGPA());
  }

  /**
     * show list student to screen
     */
  public void show() {
    for (Student student: studentList) {
      System.out.format("%5d | ", student.getId());
      System.out.format("%20s | ", student.getName());
      System.out.format("%5d | ", student.getAge());
      System.out.format("%20s | ", student.getAddress());
      System.out.format("%10.1f%n", student.getGpa());
    }
  }
  /**
     * input student id
     *
     * @return student id
     */
  public int inputId() {
    System.out.print("Input student id: ");
    while (true) {
      try {
        int id = Integer.parseInt((scanner.nextLine()));
        return id;
      } catch(NumberFormatException ex) {
        System.out.print("invalid! Input student id again: ");
      }
    }
  }
  /**
     * input student name
     *
     * @return student name
     */
  private String inputName() {
    System.out.print("Input student name: ");
    return scanner.nextLine();
  }
  /**
     * input student address
     *
     * @return student address
     */
  private String inputAddress() {
    System.out.print("Input student address: ");
    return scanner.nextLine();
  }
  /**
     * input student age
     *
     * @return student age
     */
  private byte inputAge() {
    System.out.print("Input student age: ");
    while (true) {
      try {
        byte age = Byte.parseByte((scanner.nextLine()));
        if (age < 0 && age > 100) {
          throw new NumberFormatException();
        }
        return age;
      } catch(NumberFormatException ex) {
        System.out.print("invalid! Input student id again: ");
      }
    }
  }
  /**
     * input student gpa
     *
     * @return gpa
     */
  private float inputGpa() {
    System.out.print("Input student gpa: ");
    while (true) {
      try {
        float gpa = Float.parseFloat((scanner.nextLine()));
        if (gpa < 0.0 && gpa > 10.0) {
          throw new NumberFormatException();
        }
        return gpa;
      } catch(NumberFormatException ex) {
        System.out.print("invalid! Input student age again: ");
      }
    }
  }
  // getter && setter
  public List < Student > getStudentList() {
    return studentList;
  }

  public void setStudentList(List < Student > studentList) {
    this.studentList = studentList;
  }
}

7. Tạo lớp Main.java