學生管理系統–對學生的基本資訊進行增、刪、改、查，之前使用集合完成的，程式執行資料才存在，這次使用檔案來儲存，可以使資料在硬碟中儲存，該類需要專案的根目錄下放個“student.txt”檔案-------在控制檯顯示

主類：

import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;

public class Demo {
    public static void main(String[] args) {
        System.out.println("【學生管理系統】");
        Scanner sc =
 
 new Scanner(System.in);
        while (true) {
            System.out.println("請選擇以下功能：");
            System.out.println("1、新增 2、刪除 3、修改 4、按學號查詢 5、全部查詢 6、退出");
            int op = sc.nextInt();
            switch (op) {
                case 1:
                    addStudent(sc);
                    break
 
;
                case 2:
                    deleteStudent(sc);
                    break;
                case 3:
                    updateStudent(sc);
                    break;
                case 4:
                    findById(sc);
                    break;
                case 5:
                    findAll
 
();
                    break;
                case 6:
                    System.out.println("謝謝使用，再見！");
                    System.exit(0);
                default:
                    System.out.println("輸入有誤，請重新輸入！");
            }
        }
    }

    private static void findAll() {
        ArrayList<Student> stuList = readAll();
        System.out.println("【查詢結果】");
        if (stuList == null || stuList.size() == 0) {
            System.out.println("無資料！");
        } else {
            System.out.println("============================");
            System.out.println("學號\t\t姓名\t\t性別\t\t年齡");
            for (Student student : stuList) {
                System.out.println(student.getStuNo() + "\t\t" + student.getStuName() + "\t\t"
                        + student.getStuSex() + "\t\t" + student.getStuAge());
            }
        }
    }

    private static void findById(Scanner sc) {
        ArrayList<Student> stuList = readAll();
        System.out.println("請輸入要查詢的學號：");
        int stuNo = sc.nextInt();
        System.out.println("【查詢結果】");
        for (Student student : stuList) {
            if (student.getStuNo() == stuNo) {
                System.out.println("學號\t\t姓名\t\t性別\t\t年齡");
                System.out.println(student.getStuNo() + "\t\t" + student.getStuName() + "\t\t"
                        + student.getStuSex() + "\t\t" + student.getStuAge());
                return;
            }
        }
        System.out.println("學號：" + stuNo + "--沒有找到！");
    }

    private static void updateStudent(Scanner sc) {
        ArrayList<Student> stuList = readAll();
        System.out.println("請輸入要修改的學號：");
        int stuNo = sc.nextInt();
        for (Student student : stuList) {
            if (student.getStuNo() == stuNo) {
                System.out.println("請輸入姓名：【輸入0 保留原值】");
                String name = sc.next();
                System.out.println("請輸入性別：【輸入0 保留原值】");
                String sex = sc.next();
                System.out.println("請輸入年齡：【輸入0 保留原值】");
                int age = sc.nextInt();
                if (!"0".equals(name)) {
                    student.setStuName(name);
                }
                if (!"0".equals(sex)) {
                    student.setStuSex(sex);
                }
                if (age != 0) {
                    student.setStuAge(age);
                }
                System.out.println("修改成功！");
                writeAll(stuList);
                return;
            }
        }
        System.out.println("學號：" + stuNo + "--沒有找到！");
    }

    private static void deleteStudent(Scanner sc) {
        ArrayList<Student> stuList = readAll();
        System.out.println("請輸入要刪除的學號：");
        int stuNo = sc.nextInt();
        for (Student student : stuList) {
            if (student.getStuNo() == stuNo) {
                System.out.println(student);
                System.out.println("確認是否刪除【y/n】");
                String s = sc.next();
                if ("y".equalsIgnoreCase(s)) {
                    stuList.remove(student);
                    writeAll(stuList);
                    System.out.println("刪除成功！");
                    return;
                } else {
                    System.out.println("取消操作！");
                    return;
                }
            }
        }
        System.out.println("學號："+stuNo+"--沒有找到！");
    }

    private static void addStudent(Scanner sc) {
        ArrayList<Student> stuList = readAll();
        int stuNo = 0;
        a:
        while (true) {
            System.out.println("請輸入學號：");
            stuNo = sc.nextInt();
            for (Student student : stuList) {
                if (student.getStuNo() == stuNo) {
                    System.out.println("學號：" + stuNo + "--已存在！");
                    continue a;
                }
            }
            break;
        }
        System.out.println("請輸入姓名：");
        String name = sc.next();
        System.out.println("請輸入性別：");
        String sex = sc.next();
        System.out.println("請輸入年齡：");
        int age = sc.nextInt();

        stuList.add(new Student(stuNo, name, sex, age));
        writeAll(stuList);
        System.out.println("新增成功！");
    }

    private static ArrayList<Student> readAll() {
        ArrayList<Student> stuList = new ArrayList<>();
        try (
                BufferedReader in = new BufferedReader(new FileReader("student.txt"))
        ) {
            String row = null;
            while ((row = in.readLine()) != null) {
                String[] arr = row.split(",");
                Student student = new Student();
                student.setStuNo(Integer.parseInt(arr[0]));
                student.setStuName(arr[1]);
                student.setStuSex(arr[2]);
                student.setStuAge(Integer.parseInt(arr[3]));
                stuList.add(student);
            }
            return stuList;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private static void writeAll(ArrayList<Student> stuList) {
        try (
                BufferedWriter out = new BufferedWriter(new FileWriter("student.txt"))
        ) {
            for (Student student : stuList) {
                out.write(student.getStuNo() + "," + student.getStuName() + "," + student.getStuSex() + "," + student.getStuAge());
                out.newLine();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

學生類資訊：

public class Student {
    private int stuNo;
    private String stuName;
    private String stuSex;
    private int stuAge;

    public Student() {
    }

    public Student(int stuNo, String stuName, String stuSex, int stuAge) {
        this.stuNo = stuNo;
        this.stuName = stuName;
        this.stuSex = stuSex;
        this.stuAge = stuAge;
    }

    public int getStuNo() {
        return stuNo;
    }

    public void setStuNo(int stuNo) {
        this.stuNo = stuNo;
    }

    public String getStuName() {
        return stuName;
    }

    public void setStuName(String stuName) {
        this.stuName = stuName;
    }

    public String getStuSex() {
        return stuSex;
    }

    public void setStuSex(String stuSex) {
        this.stuSex = stuSex;
    }

    public int getStuAge() {
        return stuAge;
    }

    public void setStuAge(int stuAge) {
        this.stuAge = stuAge;
    }

    @Override
    public String toString() {
        return "Student{" +
                "stuNo=" + stuNo +
                ", stuName='" + stuName + '\'' +
                ", stuSex='" + stuSex + '\'' +
                ", stuAge=" + stuAge +
                '}';
    }
}