Java中HourlyEmployee类super()调用报错：实参与形参长度不符求助

Hey there, let's break down why that super(hourly) call is throwing an error and how to fix it. That error message essentially means: the parent class doesn't have a constructor that accepts exactly the number and type of arguments you're passing to super().

What's going on here? #

When you call super(hourly) in your HourlyEmployee copy constructor, you're trying to invoke a constructor in the parent class (let's assume it's something like Employee) that takes a single HourlyEmployee (or its parent type) object as input. But your parent class probably doesn't have that constructor defined—instead, it might only have a constructor that requires multiple individual parameters (like name, employee ID, base pay, etc.), or no copy constructor at all.

Two ways to fix this: #

Option 1: If your parent class has a copy constructor

First, check if your parent class (e.g., Employee) has a copy constructor that accepts an instance of itself, like this:

public class Employee {
    private String name;
    private int employeeId;
    private double basePay;

    // Copy constructor for Employee
    public Employee(Employee other) {
        this.name = other.name;
        this.employeeId = other.employeeId;
        this.basePay = other.basePay;
    }
}

If this exists, your super(hourly) call should work! Because HourlyEmployee is a subclass of Employee, it can be upcast to Employee and passed to this constructor. Just don't forget to copy the subclass-specific fields too:

public HourlyEmployee(HourlyEmployee hourly) {
    super(hourly); // This works if parent has a copy constructor
    // Copy HourlyEmployee-specific fields
    this.hourlyRate = hourly.hourlyRate;
    this.hoursWorked = hourly.hoursWorked;
}

Option 2: If your parent class doesn't have a copy constructor

If your parent class only has a standard multi-parameter constructor, you need to pass those specific values to super() instead of the entire hourly object. For example:

public class Employee {
    private String name;
    private int employeeId;
    private double basePay;

    // Standard multi-parameter constructor
    public Employee(String name, int employeeId, double basePay) {
        this.name = name;
        this.employeeId = employeeId;
        this.basePay = basePay;
    }
}

Then your HourlyEmployee copy constructor would look like this:

public HourlyEmployee(HourlyEmployee hourly) {
    // Call the parent's constructor with values extracted from the hourly object
    super(hourly.getName(), hourly.getEmployeeId(), hourly.getBasePay());
    // Copy subclass-specific fields
    this.hourlyRate = hourly.hourlyRate;
    this.hoursWorked = hourly.hoursWorked;
}

This matches the exact parameter count and types that the parent class's constructor expects, which will resolve the "arguments differ in length" error.

Quick sanity check: #

Double-check all constructors in your parent class—none of them will have a single parameter that can accept a HourlyEmployee or Employee object if you're seeing this error. Make sure your super() call aligns with one of the parent's existing constructors.

内容的提问来源于stack exchange，提问作者user9343206