java - 构造函数中的Java可覆盖方法调用

Question

我正在做一些开始的javaing，我得到了这个错误方法

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
}

有人可以解释我的错误吗？我不想忽略这一点，因为我无法将代码扩展为子类。