Java设计模式之访问者模式的应用

// 访问者接口
interface Visitor {
    double visit(FullTimeEmployee fullTimeEmployee);
    double visit(PartTimeEmployee partTimeEmployee);
}

// 具体访问者：全职员工工资计算器
class FullTimeSalaryCalculator implements Visitor {
    @Override
    public double visit(FullTimeEmployee fullTimeEmployee) {
        return fullTimeEmployee.getMonthlySalary();
    }

    @Override
    public double visit(PartTimeEmployee partTimeEmployee) {
        // 这里不需要实现，因为访问者只访问全职员工
        throw new UnsupportedOperationException();
    }
}

// 具体访问者：兼职员工工资计算器
class PartTimeSalaryCalculator implements Visitor {
    @Override
    public double visit(FullTimeEmployee fullTimeEmployee) {
        // 这里不需要实现，因为访问者只访问兼职员工
        throw new UnsupportedOperationException();
    }

    @Override
    public double visit(PartTimeEmployee partTimeEmployee) {
        return partTimeEmployee.getHourlyWage() * partTimeEmployee.getWorkingHours();
    }
}

// 元素接口
interface Employee {
    void accept(Visitor visitor);
}

// 具体元素：全职员工
class FullTimeEmployee implements Employee {
    private double monthlySalary;

    public FullTimeEmployee(double monthlySalary) {
        this.monthlySalary = monthlySalary;
    }

    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }

    public double getMonthlySalary() {
        return monthlySalary;
    }
}

// 具体元素：兼职员工
class PartTimeEmployee implements Employee {
    private double hourlyWage;
    private double workingHours;

    public PartTimeEmployee(double hourlyWage, double workingHours) {
        this.hourlyWage = hourlyWage;
        this.workingHours = workingHours;
    }

    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }

    public double getHourlyWage() {
        return hourlyWage;
    }

    public double getWorkingHours() {
        return workingHours;
    }
}

// 对象结构：管理员工容器
class EmployeeList {
    private List<Employee> employees;

    public EmployeeList() {
        employees = new ArrayList<>();
    }

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

    public double calculateTotalSalary(Visitor visitor) {
        double totalSalary = 0;
        for (Employee employee : employees) {
            totalSalary += employee.accept(visitor);
        }
        return totalSalary;
    }
}

// 创建一个员工列表
EmployeeList employees = new EmployeeList();

// 添加全职和兼职员工
employees.addEmployee(new FullTimeEmployee(5000));
employees.addEmployee(new PartTimeEmployee(20, 80));

// 创建不同的工资计算器
FullTimeSalaryCalculator fullTimeSalaryCalculator = new FullTimeSalaryCalculator();
PartTimeSalaryCalculator partTimeSalaryCalculator = new PartTimeSalaryCalculator();

// 计算全职员工的总工资
double totalFullTimeSalary = employees.calculateTotalSalary(fullTimeSalaryCalculator);

// 计算兼职员工的总工资
double totalPartTimeSalary = employees.calculateTotalSalary(partTimeSalaryCalculator);

Total full-time salary: 5000.0
Total part-time salary: 1600.0