综合：数组版学生管理模型

public class Student {
    private int id;
    private String name;
    private int age;

    public Student(int id, String name, int age) {
        this.id = id;
        this.name = name;
        setAge(age);
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        if (age >= 0 && age <= 120) {
            this.age = age;
        } else {
            System.out.println("年龄不合法，未修改：" + age);
        }
    }

    public void printInfo() {
        System.out.println("学号：" + id + "，姓名：" + name + "，年龄：" + age);
    }
}

import java.util.Scanner;

public class StudentManager {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Student[] students = new Student[3];
        int count = 0;
        boolean running = true;

        printMenu();
        while (running) {
            System.out.println("请选择：");
            int choice = sc.nextInt();

            switch (choice) {
                case 1:
                    count = addStudent(sc, students, count);
                    break;
                case 2:
                    listStudents(students, count);
                    break;
                case 3:
                    findStudent(sc, students, count);
                    break;
                case 4:
                    updateAge(sc, students, count);
                    break;
                case 5:
                    count = deleteStudent(sc, students, count);
                    break;
                case 0:
                    running = false;
                    break;
                default:
                    System.out.println("没有这个选项，请重新输入。");
            }
        }

        System.out.println("程序结束。");
    }

    public static void printMenu() {
        System.out.println("===== 学生管理 =====");
        System.out.println("1. 添加学生");
        System.out.println("2. 列出全部");
        System.out.println("3. 按学号查找");
        System.out.println("4. 修改年龄");
        System.out.println("5. 按学号删除");
        System.out.println("0. 退出");
    }

    public static int addStudent(Scanner sc, Student[] students, int count) {
        if (count == students.length) {
            System.out.println("数组已满，不能再添加。");
            return count;
        }

        System.out.println("请输入学号：");
        int id = sc.nextInt();
        System.out.println("请输入姓名：");
        String name = sc.next();
        System.out.println("请输入年龄：");
        int age = sc.nextInt();

        students[count] = new Student(id, name, age);
        count++;
        System.out.println("添加成功，当前人数：" + count);
        return count;
    }

    public static void listStudents(Student[] students, int count) {
        if (count == 0) {
            System.out.println("还没有学生记录。");
            return;
        }

        for (int i = 0; i < count; i++) {
            students[i].printInfo();
        }
    }

    public static int findIndex(Student[] students, int count, int id) {
        for (int i = 0; i < count; i++) {
            if (students[i].getId() == id) {
                return i;
            }
        }
        return -1;
    }

    public static void findStudent(Scanner sc, Student[] students, int count) {
        System.out.println("请输入要查找的学号：");
        int id = sc.nextInt();
        int index = findIndex(students, count, id);

        if (index == -1) {
            System.out.println("没有找到学号为 " + id + " 的学生。");
        } else {
            students[index].printInfo();
        }
    }

    public static void updateAge(Scanner sc, Student[] students, int count) {
        System.out.println("请输入要修改的学号：");
        int id = sc.nextInt();
        int index = findIndex(students, count, id);

        if (index == -1) {
            System.out.println("没有找到学号为 " + id + " 的学生。");
            return;
        }

        System.out.println("请输入新的年龄：");
        int age = sc.nextInt();
        students[index].setAge(age);
        System.out.println("修改后的记录：");
        students[index].printInfo();
    }

    public static int deleteStudent(Scanner sc, Student[] students, int count) {
        System.out.println("请输入要删除的学号：");
        int id = sc.nextInt();
        int index = findIndex(students, count, id);

        if (index == -1) {
            System.out.println("没有找到学号为 " + id + " 的学生。");
            return count;
        }

        for (int i = index; i < count - 1; i++) {
            students[i] = students[i + 1];
        }
        students[count - 1] = null;
        count--;
        System.out.println("删除成功，当前人数：" + count);
        return count;
    }
}

public class CountCheck {
    public static void main(String[] args) {
        Student[] students = new Student[3];
        int count = 0;

        System.out.println("数组容量：" + students.length);
        System.out.println("当前人数：" + count);
        System.out.println("第 1 个格子：" + students[0]);
    }
}