为某公司编写一个工资支付系统，用于计算某一类员工的月薪。该公司共有四类员工：领固定月薪的（SalariedEmployee）；计时取酬的（HourlyEmployee，如果一月工时超过160小时，则还需对额外的工时支付加班费）；按销售额提成（CommissionEmployee）的和带底薪并按销售额提成的（BasePlusCommissionEmployee），其继承层次结构如下所示。已知每类员工均有表示员工工号、姓名和出生年月的属性，和用于计算员工月薪的方法。创建一个Employee变量数组，保存Employee类层次结构中每个具体类对象的引用，对每个Employee显示其工号、姓名、出生年月和月收入，如果当月是Employee的生日所在的月份，则还另发给他100月作为红包。用Java写出源码

下面是用Java实现的工资支付系统代码，包括Employee类及其子类SalariedEmployee、HourlyEmployee、CommissionEmployee和BasePlusCommissionEmployee：

import java.util.Date;

public abstract class Employee {
    private String empId;
    private String empName;
    private Date birthDate;

    public Employee(String empId, String empName, Date birthDate) {
        this.empId = empId;
        this.empName = empName;
        this.birthDate = birthDate;
    }

    public abstract double getMonthlySalary();

    public String getEmpId() {
        return empId;
    }

    public void setEmpId(String empId) {
        this.empId = empId;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public Date getBirthDate() {
        return birthDate;
    }

    public void setBirthDate(Date birthDate) {
        this.birthDate = birthDate;
    }

    public boolean isBirthday() {
        Date today = new Date();
        return (birthDate.getMonth() == today.getMonth());
    }

    public double getBirthdayBonus() {
        if (isBirthday()) {
            return 100;
        } else {
            return 0;
        }
    }
}

class SalariedEmployee extends Employee {
    private double monthlySalary;

    public SalariedEmployee(String empId, String empName, Date birthDate, double monthlySalary) {
        super(empId, empName, birthDate);
        this.monthlySalary = monthlySalary;
    }

    public double getMonthlySalary() {
        return monthlySalary + getBirthdayBonus();
    }

    public double getMonthlySalaryWithoutBonus() {
        return monthlySalary;
    }
}

class HourlyEmployee extends Employee {
    private double hourlyWage;
    private double hoursWorked;

    public HourlyEmployee(String empId, String empName, Date birthDate, double hourlyWage, double hoursWorked) {
        super(empId, empName, birthDate);
        this.hourlyWage = hourlyWage;
        this.hoursWorked = hoursWorked;
    }

    public double getMonthlySalary() {
        double overtimePay = 0;
        if (hoursWorked > 160) {
            overtimePay = (hoursWorked - 160) * hourlyWage * 1.5;
            hoursWorked = 160;
        }
        double monthlySalary = hourlyWage * hoursWorked + overtimePay;
        return monthlySalary + getBirthdayBonus();
    }

    public double getMonthlySalaryWithoutBonus() {
        double overtimePay = 0;
        if (hoursWorked > 160) {
            overtimePay = (hoursWorked - 160) * hourlyWage * 1.5;
            hoursWorked = 160;
        }
        double monthlySalary = hourlyWage * hoursWorked + overtimePay;
        return monthlySalary;
    }
}

class CommissionEmployee extends Employee {
    private double commissionRate;
    private double grossSales;

    public CommissionEmployee(String empId, String empName, Date birthDate, double commissionRate, double grossSales) {
        super(empId, empName, birthDate);
        this.commissionRate = commissionRate;
        this.grossSales = grossSales;
    }

    public double getMonthlySalary() {
        double monthlySalary = commissionRate * grossSales;
        return monthlySalary + getBirthdayBonus();
    }

    public double getMonthlySalaryWithoutBonus() {
        double monthlySalary = commissionRate * grossSales;
        return monthlySalary;
    }
}

class BasePlusCommissionEmployee extends CommissionEmployee {
    private double baseSalary;

    public BasePlusCommissionEmployee(String empId, String empName, Date birthDate, double commissionRate, double grossSales, double baseSalary) {
        super(empId, empName, birthDate, commissionRate, grossSales);
        this.baseSalary = baseSalary;
    }

    public double getMonthlySalary() {
        double monthlySalary = super.getMonthlySalary() + baseSalary;
        return monthlySalary + getBirthdayBonus();
    }

    public double getMonthlySalaryWithoutBonus() {
        double monthlySalary = super.getMonthlySalary() + baseSalary;
        return monthlySalary;
    }
}

public class PayrollSystem {
    public static void main(String[] args) {
        Date birthDate1 = new Date(2000, 1, 1);
        Employee employee1 = new SalariedEmployee("001", "John", birthDate1, 5000);

        Date birthDate2 = new Date(1995, 2, 1);
        Employee employee2 = new HourlyEmployee("002", "Mary", birthDate2, 20, 180);

        Date birthDate3 = new Date(1990, 3, 1);
        Employee employee3 = new CommissionEmployee("003", "Tom", birthDate3, 0.1, 20000);

        Date birthDate4 = new Date(1985, 4, 1);
        Employee employee4 = new BasePlusCommissionEmployee("004", "Lisa", birthDate4, 0.1, 30000, 5000);

        Employee[] employees = new Employee[]{employee1, employee2, employee3, employee4};

        for (Employee employee : employees) {
            System.out.println("Employee ID: " + employee.getEmpId());
            System.out.println("Employee Name: " + employee.getEmpName());
            System.out.println("Birth Date: " + employee.getBirthDate().toString());
            System.out.println("Monthly Salary: " + employee.getMonthlySalary());
            System.out.println();
        }
    }
}

在这个工资支付系统中，Employee类为抽象类，其中包含表示员工工号、姓名和出生年月的属性，以及用于计算员工月薪的抽象方法getMonthlySalary()。该类还包含isBirthday()和getBirthdayBonus()方法，用于判断当月是否是员工的生日所在的月份，并返回生日红包的金额。

SalariedEmployee、HourlyEmployee、CommissionEmployee和BasePlusCommissionEmployee类是Employee类的子类，它们分别表示领固定月薪、计时取酬、按销售额提成和带底薪并按销售额提成的员工。这些子类实现了getMonthlySalary()方法，根据不同的计算公式返回员工的月薪，同时调用父类的getBirthdayBonus()方法计算生日红包。

PayrollSystem类是一个测试类，其中创建了四个具体的员工对象，并将它们保存在一个Employee类型的数组中。然后，遍历该数组，对每个员工显示其工号、姓名、出生年月和月收入，其中如果当月是该员工的生日所在的月份，则还另发给他100元作为红包。