java实现：BasePlusSalesEmployee四个类的对象各一个，并计算某个月这四个对象的工资注意: 要求把每个类都做成完全封装，不允许非私有化属性。类图如下 :

你可以用如下的代码来实现:

import java.util.Scanner;

class Employee {
  private String firstName;
  private String lastName;
  private String socialSecurityNumber;

  public Employee(String firstName, String lastName, String socialSecurityNumber) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.socialSecurityNumber = socialSecurityNumber;
  }

  public String getFirstName() {
    return firstName;
  }

  public String getLastName() {
    return lastName;
  }

  public String getSocialSecurityNumber() {
    return socialSecurityNumber;
  }

  public String toString() {
    return String.format("%s %s%nsocial security number: %s", getFirstName(), getLastName(), getSocialSecurityNumber());
  }
}

class CommissionEmployee extends Employee {
  private double grossSales; // gross weekly sales
  private double commissionRate; // commission percentage

  public CommissionEmployee(String firstName, String lastName, String socialSecurityNumber, double grossSales, double commissionRate) {
    super(firstName, lastName, socialSecurityNumber);

    if (commissionRate <= 0.0 || commissionRate >= 1.0) // validate
      throw new IllegalArgumentException("Commission rate must be > 0.0 and < 1.0");

    if (grossSales < 0.0) // validate
      throw new IllegalArgumentException("Gross sales must be >= 0.0");

    this.grossSales = grossSales;
    this.commissionRate = commissionRate;
  }

  public void setGrossSales(double grossSales) {
    if (grossSales < 0.0) // validate
      throw new IllegalArgumentException("Gross sales must be >= 0.0");

    this.grossSales = grossSales;
  }

  public double getGrossSales() {
    return grossSales;
  }

  public void setCommissionRate(double commissionRate) {
    if (commissionRate <= 0.0 || commissionRate >= 1.0) // validate
      throw new IllegalArgumentException("Commission rate must be > 0.0 and < 1.0");

    this.commissionRate = commissionRate;
  }

  public double getCommissionRate() {
    return commissionRate;
  }

  public double earnings() {
    return getCommissionRate() * getGrossSales();
  }

  public String toString() {
    return String.format("%s: %s%n%s: $%,.2f; %s: %.2f", "commission employee", super.toString(), "gross sales", getGrossSales(), "commission rate", getCommissionRate());
  }
}

class BasePlusCommissionEmployee extends CommissionEmployee {
  private double baseSalary; // base salary per week

  public BasePlusCommissionEmployee(String firstName, String lastName, String socialSecurityNumber, double grossSales, double commissionRate, double baseSalary) {
    super(firstName, lastName, socialSecurityNumber, grossSales, commissionRate);

    if (baseSalary < 0.0) // validate baseSalary
      throw new IllegalArgumentException("Base salary