abstract class Employee{
   public abstract double earnings( );
}
class YearWorker extends Employee{
  【代码1】 // 重写earnings( )方法，领取总工资50000.456元
}
class MonthWorker extends Employee{
  【代码2】 // 重写earnings( )方法，每月领取工资2000元
}
class WeekWorker extends Employee{
  【代码3】 // 重写earnings( )方法，工作52周，每周工资500元
}
class Company{
   Employee[] employee;
   double salaries=0;
   Company(Employee[] employee){
      this.employee=employee;
   }
   public double salariesPay( ){
      salaries=0;
     【代码4】   // 计算salaries
      return salaries;
   }   
}
public class HardWork{
   public static void main(String args[]){
      Employee[] employee=new Employee[20];
      for(int i=0;i<employee.length;i++){
           if(i%3==0)
             employee[i]=new WeekWorker( );
           else if(i%3==1)
             employee[i]=new MonthWorker( );
           else if(i%3==2)
             employee[i]=new YearWorker( );
       }
     Company company=new Company(employee);
     System.out.println("工资总额:"+company.salariesPay( ));
   }
}

abstract class Employee{
   public abstract double earnings();
}
class YearWorker extends Employee{
  public double earnings() {
      return 50000.456;
  }
}
class MonthWorker extends Employee{
  public double earnings() {
      return 2000.0;
  }  
}
class WeekWorker extends Employee{
  public double earnings() {
      return 500.0;
  }
}
class Company{
   Employee[] employee;
   double salaries=0;
   Company(Employee[] employee){
      this.employee=employee;
   }
   public double salariesPay( ){
      salaries=0;
      for (int i=0; i<employee.length; i++) {
          salaries += employee[i].earnings();
      }
      return salaries;
   }   
}
public class HardWork{
   public static void main(String args[]){
      Employee[] employee=new Employee[20];
      for(int i=0;i<employee.length;i++){
           if(i%3==0)
             employee[i]=new WeekWorker( );
           else if(i%3==1)
             employee[i]=new MonthWorker( );
           else if(i%3==2)
             employee[i]=new YearWorker( );
       }
     Company company=new Company(employee);
     System.out.println("工资总额:"+company.salariesPay( ));
   }
}

楼上正解

楼上经常在线

恩  主要 就是 高清楚 重写和 重载  以及 抽象类 被继承后 必须 实现他的方法