如何修复“无法应用于”错误？[重复]

Question

我是Java的新手，尤其是Java的面向对象编程，我一直收到这个让我发疯的错误。

以下是我的员工超类的一部分：

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

public String getFirstName() {
    return firstName;
}

public String getLastName() {
    return lastName;
}

public String getSocialSecurityNumber() {
    return socialSecurityNumber;
}

以及子类CommissionEmployee：

public CommissionEmployee(String firstName, String lastName, 
String socialSecurityNumber, double grossSales, 
double commissionRate)
{
  this.firstName = firstName;                                    
  this.lastName = lastName;                                    
  this.socialSecurityNumber = socialSecurityNumber;         
  this.grossSales = grossSales;
  this.commissionRate = commissionRate;
}

我得到的相同错误是：

constructor Employee in class Employee cannot be applied to given types;
required: String,String,String
found: no arguments
reason: actual and formal argument lists differ in length

这到底是什么意思，是什么原因导致的，我如何修复它？

Answer 1

由于CommissionEmployee是Employee的子类，Java要求在构造CommissionEmployee时调用Employee的构造函数。默认情况下，这是对无参数构造函数Employee（）的调用，在您的情况下，该构造函数不存在。

您有两种选择：

>

public CommissionEmployee(String firstName, String lastName, 
String socialSecurityNumber, double grossSales, 
double commissionRate)
{
  super(firstName, lastName, socialSecuityNumber);  
  this.grossSales = grossSales;
  this.commissionRate = commissionRate;
}

创建一个无参数超类构造函数，并在子类构造函数中设置名字/姓氏和SSN（不太理想）。超类（Employee）构造函数受保护，因此只能由子类调用，如下所示：

protected Employee() {}