学生管理系统1.0版本有5个功能，即添加学生、删除学生、修改学生、查看全部学生、退出系统。

里面对添加重复学号、删除和修改不存在的学号等问题都有相应的解决办法。

代码区：

Student.java

package student;

//快捷键Alt+insert
public class Student {
    private String sid;
    private String name;
    private String age;
    private String address;

    public Student() {
    }

    public Student(String sid, String name, String age, String address) {
        this.sid = sid;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public String getSid() {
        return sid;
    }

    public void setSid(String sid) {
        this.sid = sid;
    }

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

StudentManager.java

package student;

import java.util.Scanner;
import java.util.ArrayList;
public class StudentManager {
    public static void main (String[] args) {
        ArrayList<Student> array = new ArrayList<Student>();
        while (true) {
            System.out.println("--------欢迎来到学生管理系统--------");
            System.out.println("1 添加学生");
            System.out.println("2 删除学生");
            System.out.println("3 修改学生");
            System.out.println("4 查看全部学生");
            System.out.println("5 退出系统");

                System.out.println("请输入你的选择：");
                Scanner sc = new Scanner(System.in);
                String line = sc.nextLine();
                switch (line) {
                    case "1":
                        //System.out.println("添加学生");
                        addStudent(array);
                        break;
                    case "2":
                        //System.out.println("删除学生");
                        deleteStudent(array);
                        break;
                    case "3":
                        //System.out.println("修改学生");
                        updateStudent(array);
                        break;
                    case "4":
                        findAllStudent(array);
                        //System.out.println("查看所有学生");
                        break;
                    case "5":
                        System.out.println("退出系统");
                        System.exit(0); //直接退出java虚拟机
                    default:
                        System.out.println("操作错误，请重新输入：");
                }
        }
    }
    //添加功能
    public  static void addStudent(ArrayList<Student> array) {
        Scanner sc = new Scanner(System.in);//刘正风，嵩山
        String sid;
        System.out.println("请输入学生学号：");//风清扬，华山，岳不群，华山
        while(true) {
            int index=-1;
            sid = sc.nextLine();
            for (int i = 0; i < array.size(); i++) {
                Student s = array.get(i);
                if (s.getSid().equals(sid)) {
                    index=i;
                    break;
                }
            }
            if(index==-1)
                break;
            else
                System.out.println("你输入的学号已被使用，请重新输入学号：");
        }
        System.out.println("请输入学生姓名：");
        String name = sc.nextLine();
        System.out.println("请输入学生年龄：");
        String age = sc.nextLine();
        System.out.println("请输入学生地址：");
        String address = sc.nextLine();

        //创建学生对象
        Student s = new Student();
        s.setSid(sid);
        s.setName(name);
        s.setAge(age);
        s.setAddress(address);
        //添加学生对象到集合中
        array.add(s);
        System.out.println("添加成功！");
    }
    //查询功能
    public static void findAllStudent(ArrayList<Student> array) {
        if(array.size()==0){
            System.out.println("无信息！请先添加信息再查询！");
            return ;
        }
        System.out.println("学号\t\t姓名\t\t年龄\t\t地址");
        for(int i=0;i<array.size();i++) {
            Student s = array.get(i);
            System.out.println(s.getSid()+"\t"+s.getName()+"\t"+s.getAge()+"\t\t"+s.getAddress());
        }
    }
    //删除功能
    public static void deleteStudent(ArrayList<Student> array) {
        if(array.size()==0){
            System.out.println("无信息！请先添加信息再删除！");
            return ;
        }
        Scanner sc = new Scanner(System.in);
        String sid;
        int index=-1;
        System.out.println("请输入你要删除的学生的学号：");
        while(true) {
            sid = sc.nextLine();
            for (int i = 0; i < array.size(); i++) {
                Student s = array.get(i);
                if (s.getSid().equals(sid)) {
                    index=i;
                    break;
                }
            }
            if(index==-1)
                System.out.println("该学生不存在！\n请重新输入你要删除的学生的学号:");
            else {
                array.remove(index);
                System.out.println("删除成功！");
                break;
            }
        }
    }
    //修改功能
    public static void updateStudent(ArrayList<Student> array) {
        if(array.size()==0){
            System.out.println("无信息！请先添加信息！");
            return ;
        }
        Scanner sc = new Scanner(System.in);
        String sid;
        int index=-1;
        System.out.println("请输入你要修改的学生的学号：");
        while(true) {
            sid = sc.nextLine();
            for (int i = 0; i < array.size(); i++) {
                Student s1 = array.get(i);
                if (s1.getSid().equals(sid)) {
                    index = i;
                    break;
                }
            }
            if (index==-1) {
                System.out.println("该学生不存在！\n请重新输入你要修改的学生的学号:");
            }
            else
                break;
        }
        System.out.println("请输入学生新姓名：");
        String name = sc.nextLine();
        System.out.println("请输入学生新年龄：");
        String age = sc.nextLine();
        System.out.println("请输入学生新地址：");
        String address = sc.nextLine();
        Student s = new Student();
        s.setSid(sid);
        s.setAge(age);
        s.setName(name);
        s.setAddress(address);
        array.set(index,s);
        System.out.println("修改成功！");
    }
}

部分运行结果：