題目：

源代碼：

Student類：

public class Student {
    private String nid;
    private String name;
    private String age;
    private String address;

    public Student() {}

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

    public String getNid() {
        return nid;
    }

    public void setNid(String nid) {
        this.nid = nid;
    }

    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;
    }
}

test測驗類：

import java.util.Scanner;
import java.util.ArrayList;
public class test {
    public static void main(String[] args) {
        //創建Student型別的集合:存盤Student型別的元素
        ArrayList<Student> array = new ArrayList<Student>();

        while (true) {
            //主界面
            System.out.println("------------------------------");
            System.out.println("歡迎來到學生資訊管理系統");
            System.out.println("1:添加學生");
            System.out.println("2:洗掉學生");
            System.out.println("3:修改學生");
            System.out.println("4:顯示所有學生資訊");
            System.out.println("5:退出系統");
            System.out.println("請輸入你的指令:");

            //輸入指令
            Scanner sc = new Scanner(System.in);
            String line = sc.nextLine();


            switch (line) {
                case "1":
                    addStudent(array);//呼叫添加函式
                    break;
                case "2":
                    deleteStudent(array);//呼叫洗掉函式
                    break;
                case "3":
                    updateStudent(array);//呼叫修改函式
                    break;
                case "4":
                    findAllStudent(array);//呼叫查詢函式
                    break;
                case "5":
                    System.out.println("謝謝使用");
                    System.exit(0);
                default:
                    System.out.println("你輸入的指令有誤，請重新輸入：");
                    break;
            }
        }
    }

    //方法:添加學生
    public static void addStudent(ArrayList<Student> array){
        Scanner sc = new Scanner(System.in);

        System.out.println("請輸入被添加的學生的學號:");
        String nid = sc.nextLine();
        for(int i=0;i<array.size();i++){
            Student s1 = array.get(i);
            if(s1.getNid().equals(nid)==true){
                System.out.println("該學號所對應的學生已存在");
                return;
            }
        }
        System.out.println("請輸入被添加的學生的姓名:");
        String name = sc.nextLine();
        System.out.println("請輸入被添加的學生的年齡:");
        String age = sc.nextLine();
        System.out.println("請輸入被添加的學生的地址:");
        String address = sc.nextLine();

        //創建Student型別的物件s
        Student s = new Student(nid,name,age,address);

        //將物件添加到集合中
        array.add(s);
        System.out.println("添加成功");
    }
    //方法:顯示所有學生資訊
    public static void findAllStudent(ArrayList<Student> array){
        if(array.size()==0){
            System.out.println("請先添加學生資訊，再查詢學生資訊");
            return;
        }

        System.out.println("學號\t姓名\t年齡\t住址");

        //遍歷輸出集合中的物件里的每個元素
        for(int j=0;j< array.size();j++){
            Student s = array.get(j);
            System.out.println(s.getNid()+"\t"+s.getName()+"\t"+s.getAge()+"\t"+s.getAddress());
        }
    }
    //方法:洗掉學生
    public static void deleteStudent(ArrayList<Student> array){
        System.out.println("請輸入你要洗掉的學生的學號：");

        Scanner sc = new Scanner(System.in);
        String number = sc.nextLine();

        int flag = -1;//用來判斷輸入的學號存不存在
        for(int i = 0;i< array.size();i++){
            Student s = array.get(i);
            if(s.getNid().equals(number)==true){
                array.remove(i);
                System.out.println("洗掉成功");
                flag = 1;
                break;
            }
        }
        if(flag == -1){//如果flag=-1，說明前邊的遍歷沒找到需要洗掉的學號
            System.out.println("你輸入的學號對應的學生不存在");
        }

    }
    //方法:修改學生資訊
    public static void updateStudent(ArrayList<Student> array){
        Scanner sc = new Scanner(System.in);
        System.out.println("請輸入你想要修改資訊的學生的學號:");
        String number = sc.nextLine();

        int flag = -1;//用來判斷輸入的學號存不存在
        for(int i=0;i<array.size();i++){
            Student s = array.get(i);
            if(s.getNid().equals(number)==true){
                System.out.println("修改后的學號:");
                String nid = sc.nextLine();
                System.out.println("修改后的姓名:");
                String name = sc.nextLine();
                System.out.println("修改后的年齡:");
                String age  = sc.nextLine();
                System.out.println("修改后的地址:");
                String address = sc.nextLine();

                array.get(i).setNid(nid);
                array.get(i).setName(name);
                array.get(i).setAge(age);
                array.get(i).setAddress(address);
                System.out.println("修改成功");
                flag = 1;
                break;
            }
        }
        if(flag == -1){//如果flag=-1，說明前邊的遍歷沒找到需要修改的學號
            System.out.println("你輸入的學號對應的學生不存在");
        }
    }
}