MVC/MainApp.java

package com.studentmanagement;

import com.studentmanagement.controller.StudentController;
import com.studentmanagement.model.Student;
import com.studentmanagement.view.StudentConsoleView;
import com.studentmanagement.exception.StudentNotFoundException;
import com.studentmanagement.exception.DuplicateStudentException;
import com.studentmanagement.util.InputUtil;

/**
 * 主应用程序类，系统入口点
 * 初始化MVC组件并启动用户界面
 */
public class MainApp {
    private StudentController controller;
    private StudentConsoleView view;

    /**
     * 构造函数，初始化控制器和视图
     */
    public MainApp() {
        this.controller = new StudentController();
        this.view = new StudentConsoleView();
    }

    /**
     * 启动应用程序
     */
    public void start() {
        view.displayWelcome();
        boolean running = true;

        while (running) {
            view.displayMenu();
            int choice = InputUtil.getIntInput("", 0, 9);
            view.displaySeparator();

            switch (choice) {
                case 1:
                    displayAllStudents();
                    break;
                case 2:
                    findStudentById();
                    break;
                case 3:
                    addNewStudent();
                    break;
                case 4:
                    updateStudent();
                    break;
                case 5:
                    deleteStudent();
                    break;
                case 6:
                    findStudentsByCourse();
                    break;
                case 7:
                    findStudentsWithHighGrades();
                    break;
                case 8:
                    showCourseAverageGrade();
                    break;
                case 9:
                    showAverageAge();
                    break;
                case 0:
                    running = false;
                    view.displayExit();
                    break;
            }
        }
        InputUtil.close();
    }

    /**
     * 显示所有学生
     */
    private void displayAllStudents() {
        view.displayStudentList(controller.getAllStudents());
    }

    /**
     * 根据ID查找学生
     */
    private void findStudentById() {
        int id = InputUtil.getIntInput("请输入学生ID: ");
        try {
            Student student = controller.getStudentById(id);
            view.displayStudent(student);
        } catch (StudentNotFoundException e) {
            view.displayErrorMessage(e.getMessage());
        }
    }

    /**
     * 添加新学生
     */
    private void addNewStudent() {
        int id = InputUtil.getIntInput("请输入学生ID: ");
        String name = InputUtil.getNonEmptyStringInput("请输入学生姓名: ");
        int age = InputUtil.getIntInput("请输入学生年龄: ", 1, 100);
        String course = InputUtil.getNonEmptyStringInput("请输入课程名称: ");
        double grade = InputUtil.getDoubleInput("请输入成绩: ", 0, 100);

        Student student = new Student(id, name, age, course, grade);
        try {
            controller.addStudent(student);
            view.displaySuccessMessage("学生添加成功！");
        } catch (DuplicateStudentException e) {
            view.displayErrorMessage(e.getMessage());
        }
    }

    /**
     * 更新学生信息
     */
    private void updateStudent() {
        int id = InputUtil.getIntInput("请输入要更新的学生ID: ");
        try {
            Student existingStudent = controller.getStudentById(id);
            view.displayStudent(existingStudent);
            
            String name = InputUtil.getStringInput("请输入新姓名 (留空保持不变): ");
            String course = InputUtil.getStringInput("请输入新课程 (留空保持不变): ");
            
            // 只有在用户输入了新值时才更新
            if (name.isEmpty()) name = existingStudent.getName();
            if (course.isEmpty()) course = existingStudent.getCourse();
            
            int age = InputUtil.getIntInput("请输入新年龄 (0保持不变): ", 0, 100);
            if (age == 0) age = existingStudent.getAge();
            
            double grade = InputUtil.getDoubleInput("请输入新成绩 (-1保持不变): ", -1, 100);
            if (grade == -1) grade = existingStudent.getGrade();
            
            Student updatedStudent = new Student(id, name, age, course, grade);
            controller.updateStudent(updatedStudent);
            view.displaySuccessMessage("学生信息更新成功！");
        } catch (StudentNotFoundException e) {
            view.displayErrorMessage(e.getMessage());
        }
    }

    /**
     * 删除学生
     */
    private void deleteStudent() {
        int id = InputUtil.getIntInput("请输入要删除的学生ID: ");
        try {
            controller.deleteStudent(id);
            view.displaySuccessMessage("学生删除成功！");
        } catch (StudentNotFoundException e) {
            view.displayErrorMessage(e.getMessage());
        }
    }

    /**
     * 根据课程查找学生
     */
    private void findStudentsByCourse() {
        String course = InputUtil.getNonEmptyStringInput("请输入课程名称: ");
        view.displayStudentList(controller.getStudentsByCourse(course));
    }

    /**
     * 查找成绩优秀的学生
     */
    private void findStudentsWithHighGrades() {
        view.displayStudentList(controller.getStudentsByGradeAbove(90));
    }

    /**
     * 显示课程平均成绩
     */
    private void showCourseAverageGrade() {
        String course = InputUtil.getNonEmptyStringInput("请输入课程名称: ");
        double average = controller.calculateAverageGradeByCourse(course);
        view.displayStatistics("课程《" + course + "》的平均成绩为: " + String.format("%.2f", average));
    }

    /**
     * 显示学生平均年龄
     */
    private void showAverageAge() {
        double averageAge = controller.calculateAverageAge();
        view.displayStatistics("所有学生的平均年龄为: " + String.format("%.2f", averageAge));
    }

    /**
     * 主方法，应用程序入口
     */
    public static void main(String[] args) {
        MainApp app = new MainApp();
        app.start();
    }
}