在构造函数中调用Java Overridable方法

Question

我正在做一些开始javaing，我一直在为

获取此错误方法

public CommissionEmployee(String firstName, String lastName, String SocialSecurityNumber, double GrossSales, double commissionRate) {
//implicit call to Object constructor occurs here
this.firstName = firstName;
this.lastName = lastName; 
this.SocialSecurityNumber = SocialSecurityNumber;
setGrossSales(7500.0); //validate and store gross Sales
setCommissionRate(.05); //Validate and Store Commission Rate
}

有人可以解释一下我的错误吗？我不想忽略这一点，因为我无法将代码扩展到子类中。