Why does an exception occur when a subclass calls an overloaded method?

Why does an exception occur when a subclass calls an overloaded method?

In object-oriented programming, overloading refers to defining multiple methods in the same class. These methods have the same name but different parameter lists to achieve different functional implementations. When a subclass inherits from a parent class, if there is an overload of a method with the same name in the subclass, exceptions may occur.

To explain more specifically why an exception is thrown when a subclass calls an overloaded method, let's look at the following code example:

class Parent {
    void display() {
        System.out.println("Parent class display method");
    }
    void display(int num) {
        System.out.println("Parent class display method with parameter");
    }
}

class Child extends Parent {
    void display() {
        System.out.println("Child class display method");
    }
}

public class Main {
    public static void main(String[] args) {
        Parent parent = new Child();
        parent.display();
        parent.display(10);
    }
}

In the above code, we define a parent class Parent and a subclass Child. There are two overloaded display methods in the parent class, which are the version without parameters and the one with an integer parameter. Version. The subclass Child inherits from the parent class Parent, and overrides the display method in the parent class.

In the Main class, we create a reference from the parent class to the object of the subclass. Then try calling the display method and the display(int num) method respectively. According to the principle of polymorphism, since the reference variable is of the parent class type and the actual object is of the subclass type, the method in the subclass Child should be called.

However, when you run the program, you will find that only the display method is called, and a compilation error will occur when calling the display(int num) method. This is because in the inheritance relationship, when a subclass overrides the method of the parent class, it does not overwrite the method of the parent class, but only adds a new overloaded method. Therefore, when an overloaded method is called through a parent class reference, the compiler will choose to call the method defined in the parent class rather than the overloaded method in the child class.

In order to solve this problem, we can declare the methods in the parent class as final, or overload all methods in the parent class in the child class to ensure that the child is called Method in a class without throwing an exception.

To sum up, exceptions will be thrown when subclasses call overloaded methods because in the inheritance relationship, subclasses overloading the methods of the parent class will not override the methods of the parent class, so you need to pay attention when using to avoid this situation.

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