基础排版效果

  1import java.util.ArrayList;
  2import java.util.List;
  3import java.util.Scanner;
  4
  5/**
  6 * 学生成绩管理系统 - Java Demo
  7 * 功能：添加、查看、删除、修改学生成绩
  8 */
  9public class StudentGradeSystem {
 10    private List<Student> students;
 11    private Scanner scanner;
 12
 13    public StudentGradeSystem() {
 14        students = new ArrayList<>();
 15        scanner = new Scanner(System.in);
 16    }
 17
 18    // 学生内部类
 19    static class Student {
 20        private int id;
 21        private String name;
 22        private double score;
 23
 24        public Student(int id, String name, double score) {
 25            this.id = id;
 26            this.name = name;
 27            this.score = score;
 28        }
 29
 30        public int getId() { return id; }
 31        public String getName() { return name; }
 32        public double getScore() { return score; }
 33
 34        @Override
 35        public String toString() {
 36            return String.format("学号: %d, 姓名: %s, 成绩: %.2f", id, name, score);
 37        }
 38    }
 39
 40    // 添加学生
 41    public void addStudent() {
 42        System.out.print("请输入学号: ");
 43        int id = scanner.nextInt();
 44        scanner.nextLine(); // 消耗换行符
 45
 46        System.out.print("请输入姓名: ");
 47        String name = scanner.nextLine();
 48
 49        System.out.print("请输入成绩: ");
 50        double score = scanner.nextDouble();
 51
 52        students.add(new Student(id, name, score));
 53        System.out.println("✅ 学生添加成功！\n");
 54    }
 55
 56    // 显示所有学生
 57    public void showAllStudents() {
 58        if (students.isEmpty()) {
 59            System.out.println("⚠️ 暂无学生数据\n");
 60            return;
 61        }
 62
 63        System.out.println("📊 所有学生成绩:");
 64        for (Student s : students) {
 65            System.out.println(s);
 66        }
 67        System.out.println();
 68    }
 69
 70    // 查找学生
 71    public void findStudent() {
 72        System.out.print("请输入要查找的学号: ");
 73        int id = scanner.nextInt();
 74
 75        for (Student s : students) {
 76            if (s.getId() == id) {
 77                System.out.println("🔍 找到学生: " + s + "\n");
 78                return;
 79            }
 80        }
 81        System.out.println("❌ 未找到该学生\n");
 82    }
 83
 84    // 删除学生
 85    public void deleteStudent() {
 86        System.out.print("请输入要删除的学号: ");
 87        int id = scanner.nextInt();
 88
 89        boolean removed = students.removeIf(s -> s.getId() == id);
 90        if (removed) {
 91            System.out.println("🗑️ 学生删除成功！\n");
 92        } else {
 93            System.out.println("❌ 未找到该学生\n");
 94        }
 95    }
 96
 97    // 修改学生成绩
 98    public void updateStudent() {
 99        System.out.print("请输入要修改的学号: ");
100        int id = scanner.nextInt();
101
102        for (Student s : students) {
103            if (s.getId() == id) {
104                System.out.print("请输入新的成绩: ");
105                double newScore = scanner.nextDouble();
106                // 由于字段是private，需要通过反射或重新创建对象
107                // 这里简单演示，实际可添加setter方法
108                students.set(students.indexOf(s),
109                    new Student(s.getId(), s.getName(), newScore));
110                System.out.println("✅ 成绩修改成功！\n");
111                return;
112            }
113        }
114        System.out.println("❌ 未找到该学生\n");
115    }
116
117    // 计算平均分
118    public void calculateAverage() {
119        if (students.isEmpty()) {
120            System.out.println("⚠️ 暂无学生数据\n");
121            return;
122        }
123
124        double sum = 0;
125        for (Student s : students) {
126            sum += s.getScore();
127        }
128        double avg = sum / students.size();
129        System.out.printf("📈 平均成绩: %.2f\n\n", avg);
130    }
131
132    // 显示菜单
133    public void showMenu() {
134        System.out.println("=== 📚 学生成绩管理系统 ===");
135        System.out.println("1. 添加学生");
136        System.out.println("2. 查看所有学生");
137        System.out.println("3. 查找学生");
138        System.out.println("4. 删除学生");
139        System.out.println("5. 修改成绩");
140        System.out.println("6. 计算平均分");
141        System.out.println("0. 退出系统");
142        System.out.print("请选择操作: ");
143    }
144
145    // 运行系统
146    public void run() {
147        System.out.println("🎓 欢迎使用学生成绩管理系统！\n");
148
149        while (true) {
150            showMenu();
151            int choice = scanner.nextInt();
152            System.out.println();
153
154            switch (choice) {
155                case 1 -> addStudent();
156                case 2 -> showAllStudents();
157                case 3 -> findStudent();
158                case 4 -> deleteStudent();
159                case 5 -> updateStudent();
160                case 6 -> calculateAverage();
161                case 0 -> {
162                    System.out.println("👋 感谢使用，再见！");
163                    scanner.close();
164                    return;
165                }
166                default -> System.out.println("❌ 无效选项，请重新选择\n");
167            }
168        }
169    }
170
171    // 主方法
172    public static void main(String[] args) {
173        StudentGradeSystem system = new StudentGradeSystem();
174        system.run();
175    }
176}