在工资支付系统中，雇员的记录由：雇员号（int）、姓名（String）、地址（String）和工资（double）组成。编写一个程序完成雇员记录的添加、修改、删除、查询功能。要求在系统退出时将系统所有的雇员记录写入文件中；在下次进入系统时，从该文件中恢复雇员信息。Java

好的，这是一个比较典型的CRUD操作程序，可以通过Java面向对象的方式实现。以下是一个简单的实现，具体细节可以根据实际需求进行调整：

import java.io.*;
import java.util.*;

class Employee implements Serializable {
    private int id;
    private String name;
    private String address;
    private double salary;

    public Employee(int id, String name, String address, double salary) {
        this.id = id;
        this.name = name;
        this.address = address;
        this.salary = salary;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAddress() {
        return address;
    }

    public double getSalary() {
        return salary;
    }

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

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public String toString() {
        return "ID: " + id + ", Name: " + name + ", Address: " + address + ", Salary: " + salary;
    }
}

class EmployeeSystem {
    private List<Employee> employees;
    private String filename;

    public EmployeeSystem(String filename) {
        this.filename = filename;
        employees = new ArrayList<>();
        loadFromFile();
    }

    private void loadFromFile() {
        try {
            FileInputStream file = new FileInputStream(filename);
            ObjectInputStream in = new ObjectInputStream(file);
            employees = (List<Employee>) in.readObject();
            in.close();
            file.close();
        } catch (IOException | ClassNotFoundException e) {
            System.out.println("Failed to load employees from file: " + filename);
        }
    }

    private void saveToFile() {
        try {
            FileOutputStream file = new FileOutputStream(filename);
            ObjectOutputStream out = new ObjectOutputStream(file);
            out.writeObject(employees);
            out.close();
            file.close();
        } catch (IOException e) {
            System.out.println("Failed to save employees to file: " + filename);
        }
    }

    public void addEmployee(Employee employee) {
        employees.add(employee);
        saveToFile();
    }

    public void updateEmployee(int id, String address, double salary) {
        for (Employee employee : employees) {
            if (employee.getId() == id) {
                employee.setAddress(address);
                employee.setSalary(salary);
                saveToFile();
                return;
            }
        }
        System.out.println("Employee not found: " + id);
    }

    public void deleteEmployee(int id) {
        Iterator<Employee> it = employees.iterator();
        while (it.hasNext()) {
            Employee employee = it.next();
            if (employee.getId() == id) {
                it.remove();
                saveToFile();
                return;
            }
        }
        System.out.println("Employee not found: " + id);
    }

    public void queryEmployee(int id) {
        for (Employee employee : employees) {
            if (employee.getId() == id) {
                System.out.println(employee);
                return;
            }
        }
        System.out.println("Employee not found: " + id);
    }

    public void printAllEmployees() {
        for (Employee employee : employees) {
            System.out.println(employee);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        EmployeeSystem system = new EmployeeSystem("employees.dat");
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("1. Add employee");
            System.out.println("2. Update employee");
            System.out.println("3. Delete employee");
            System.out.println("4. Query employee");
            System.out.println("5. Print all employees");
            System.out.println("0. Exit");
            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    System.out.println("Enter employee ID:");
                    int id = scanner.nextInt();
                    scanner.nextLine();
                    System.out.println("Enter employee name:");
                    String name = scanner.nextLine();
                    System.out.println("Enter employee address:");
                    String address = scanner.nextLine();
                    System.out.println("Enter employee salary:");
                    double salary = scanner.nextDouble();
                    Employee employee = new Employee(id, name, address, salary);
                    system.addEmployee(employee);
                    break;
                case 2:
                    System.out.println("Enter employee ID:");
                    id = scanner.nextInt();
                    scanner.nextLine();
                    System.out.println("Enter new address (or leave blank to skip):");
                    address = scanner.nextLine();
                    System.out.println("Enter new salary (or leave blank to skip):");
                    String salaryStr = scanner.nextLine();
                    if (!address.isBlank()) {
                        if (!salaryStr.isBlank()) {
                            salary = Double.parseDouble(salaryStr);
                            system.updateEmployee(id, address, salary);
                        } else {
                            system.updateEmployee(id, address, 0);
                        }
                    } else if (!salaryStr.isBlank()) {
                        salary = Double.parseDouble(salaryStr);
                        system.updateEmployee(id, "", salary);
                    } else {
                        System.out.println("No changes made.");
                    }
                    break;
                case 3:
                    System.out.println("Enter employee ID:");
                    id = scanner.nextInt();
                    system.deleteEmployee(id);
                    break;
                case 4:
                    System.out.println("Enter employee ID:");
                    id = scanner.nextInt();
                    system.queryEmployee(id);
                    break;
                case 5:
                    system.printAllEmployees();
                    break;
                case 0:
                    return;
                default:
                    System.out.println("Invalid choice.");
            }
        }
    }
}

这个程序使用了一个Employee类来表示每个雇员，一个EmployeeSystem类来管理所有的雇员记录。Employee类实现了Serializable接口，这样就可以将它们存储到文件中。EmployeeSystem类提供了添加、修改、删除、查询和打印所有雇员记录的方法，这些方法都会在相应的操作后将所有雇员记录写入文件中。程序的主函数使用一个简单的菜单来调用这些方法，同时在启动时从文件中恢复所有雇员记录。