Bài tập quản lý sinh viên trong Java

package vn.kienthuclaptrinh;

import java.io.Serializable;

/**
 * Student class
 * 
 * @author kienthuclaptrinh.net
 */
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;
    }
}

package vn.kienthuclaptrinh;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * StudentDao class
 * 
 * @author kienthuclaptrinh.net
 */
public class StudentDao {
    private static final String STUDENT_FILE_NAME = "student.txt";

    /**
     * save list student to file
     * 
     * @param studentList: list student to save
     */
    public void write(List<Student> studentList) {
        FileOutputStream fos = null;
        ObjectOutputStream oos = null;
        try {
            fos = new FileOutputStream(new File(STUDENT_FILE_NAME));
            oos = new ObjectOutputStream(fos);
            oos.writeObject(studentList);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            closeStream(fos);
            closeStream(oos);
        }
    }

    /**
     * read list student from file
     * 
     * @return list student
     */
    public List<Student> read() {
        List<Student> studentList = new ArrayList<>();
        FileInputStream fis = null;
        ObjectInputStream ois = null;
        try {
            fis = new FileInputStream(new File(STUDENT_FILE_NAME));
            ois = new ObjectInputStream(fis);
            studentList = (List<Student>) ois.readObject();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            closeStream(fis);
            closeStream(ois);
        }
        return studentList;
    }

    /**
     * close input stream
     * 
     * @param is: input stream
     */
    private void closeStream(InputStream is) {
        if (is != null) {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * close output stream
     * 
     * @param os: output stream
     */
    private void closeStream(OutputStream os) {
        if (os != null) {
            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

package vn.kienthuclaptrinh;

import java.util.Comparator;

/**
 * SortStudentByGPA class
 * 
 * @author kienthuclaptrinh.net
 */
public class SortStudentByGPA implements Comparator<Student> {
    @Override
    public int compare(Student student1, Student student2) {
        if (student1.getGpa() > student2.getGpa()) {
            return 1;
        }
        return -1;
    }
}

File: SortStudentByName.java

package vn.kienthuclaptrinh;

import java.util.Comparator;

/**
 * SortStudentByName class
 * 
 * @author kienthuclaptrinh.net
 */
public class SortStudentByName implements Comparator<Student> {
    @Override
    public int compare(Student student1, Student student2) {
        return student1.getName().compareTo(student2.getName());
    }
}

package vn.kienthuclaptrinh;

import java.util.Collections;
import java.util.List;
import java.util.Scanner;

/**
 * StudentManager class
 * 
 * @author kienthuclaptrinh.net
 */
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;
    }
}

package vn.kienthuclaptrinh;

import java.util.Scanner;

/**
 * Main class
 * 
 * @author kienthuclaptrinh.net
 */
public class Main {
    public static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        String choose = null;
        boolean exit = false;
        StudentManager studentManager = new StudentManager();
        int studentId;

        // show menu
        showMenu();
        while (true) {
            choose = scanner.nextLine();
            switch (choose) {
            case "1":
                studentManager.add();
                break;
            case "2":
                studentId = studentManager.inputId();
                studentManager.edit(studentId);
                break;
            case "3":
                studentId = studentManager.inputId();
                studentManager.delete(studentId);
                break;
            case "4":
                studentManager.sortStudentByGPA();
                break;
            case "5":
                studentManager.sortStudentByName();
                break;
            case "6":
                studentManager.show();
                break;
            case "0":
                System.out.println("exited!");
                exit = true;
                break;
            default:
                System.out.println("invalid! please choose action in below menu:");
                break;
            }
            if (exit) {
                break;
            }
            // show menu
            showMenu();
        }
    }

    /**
     * create menu
     */
    public static void showMenu() {
        System.out.println("-----------menu------------");
        System.out.println("1. Add student.");
        System.out.println("2. Edit student by id.");
        System.out.println("3. Delete student by id.");
        System.out.println("4. Sort student by gpa.");
        System.out.println("5. Sort student by name.");
        System.out.println("6. Show student.");
        System.out.println("0. exit.");
        System.out.println("---------------------------");
        System.out.print("Please choose: ");
    }
}