Java学生管理系统（控制台）实现了学生姓名，学号，居住地，年龄的添加，删除，修改，查询。解决了学号的重复问题，不存在的问题等

package com.itheima; import java.util.ArrayList; import java.util.Scanner; public class studentdemo { public static boolean isused(ArrayList<Student> array, String sid) { boolean flag = false; for (int i = 0; i < array.size(); i++) { Student s = array.get(i); if (s.getSid().equals(sid)) { flag = true; break; } } return flag; } public static void updateStudent(ArrayList<Student> array) { Scanner sc = new Scanner(System.in); System.out.println("请输入你要修改学生的学号:"); String sid = sc.nextLine(); System.out.println("请输入学生的新学号:"); String sid1 = sc.nextLine(); System.out.println("请输入学生的新姓名:"); String name = sc.nextLine(); System.out.println("请输入学生的新年龄:"); String age = sc.nextLine(); System.out.println("请输入学生的新地址:"); String address = sc.nextLine(); //创建新的对象 Student st = new Student(sid1, name, age, address); //把新的对象替换原有对象 for (int i = 0; i < array.size(); i++) { Student s = array.get(i); if (s.getSid().equals(sid)) { array.set(i, st); break; } } System.out.println("修改学生信息成功"); } public static void deleteStudent(ArrayList<Student> array) { System.out.println("请输入你要删除的学号:"); Scanner sc = new Scanner(System.in); String s1 = sc.nextLine(); int index = -1; for (int i = 0; i < array.size(); i++) { Student s = array.get(i); if (s.getSid().equals(s1)) { index = i; break; } } if (index == -1) { System.out.println("该学号有误或不存在，请重新输入！"); } else { array.remove(index); System.out.println("删除学生信息成功"); } } public static void findAllStudent(ArrayList<Student> array) { if (array.size() == 0) { System.out.println("无学生信息可查询，请添加后再查询！"); //为了让程序不往下执行，给出return 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\t" + s.getName() + "\t" + s.getAge() + "\t\t" + s.getAddress()); } } //添加学生信息 public static void addStudent(ArrayList<Student> array) { Scanner sc = new Scanner(System.in); String sid; while (true) { System.out.println("请输入你的学号:"); sid = sc.nextLine(); boolean flag = isused(array, sid); if (flag == true) { System.out.println("该学号已被使用，请重新输入！"); } else break; } System.out.println("请输入你的姓名:"); String name = sc.nextLine(); System.out.println("请输入你的年龄:"); String age = sc.nextLine(); System.out.println("请输入你的地址:"); String address = sc.nextLine(); Student s = new Student(sid, name, age, address); array.add(s); System.out.println("添加学生信息成功"); } public static void main(String[] args) { //创建学生对象，用于存储学生信息 ArrayList<Student> array = new ArrayList<Student>(); do { 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 查看所有学生"); System.out.println("5 退出"); System.out.println("请输入你的选择:"); Scanner i = new Scanner(System.in); int input = i.nextInt(); switch (input) { case 1: // System.out.println("1 添加学生"); addStudent(array); break; case 2: // System.out.println("2 删除学生"); deleteStudent(array); break; case 3: // System.out.println("3 修改学生"); updateStudent(array); break; case 4: // System.out.println("4 查看所有学生"); findAllStudent(array); break; case 5: System.out.println("谢谢使用"); System.exit(0); } } while (true); } }