Method Overriding In Java

Method overriding is a feature in object-oriented programming that allows a subclass to provide a different implementation of a method that is already defined in its superclass. This enables the subclass to inherit the properties and behavior of the superclass and to override the methods that are not appropriate for its specific needs.

In Java, there are several cases where method overriding cannot be used:

1. Final methods: If a method is declared as final in the superclass, it cannot be overridden in the subclass. This is because a final method is considered to be complete and cannot be changed by any subclasses.
2. Static methods: If a method is declared as static in the superclass, it cannot be overridden in the subclass. This is because a static method is associated with the class and not with an instance of an object.
3. Private methods: If a method is declared as private in the superclass, it cannot be overridden in the subclass. This is because a private method is not accessible outside of the class in which it is declared, and therefore cannot be overridden by subclasses.
4. Return type: The return type of the overriding method must be the same or a subtype of the return type of the overridden method. This means that if the return type of the overridden method is "Object", the overriding method can return any type of object but if the return type of the overridden method is "String" the overriding method must also return a "String".
5. Access level: The access level of the overriding method must be the same or more restrictive than the overridden method. This means that if the overridden method is declared as "public", the overriding method can also be declared as "public" or as "protected" but it cannot be declared as "private"
6. Checked exceptions: If the overridden method throws a checked exception, the overriding method must also throw the same exception or an exception that is a subclass of the exception thrown by the overridden method. This ensures that the overriding method can handle the exception in a way that is compatible with the overridden method.
7. Constructors: Constructors cannot be overridden in Java, but they can be overloaded. A constructor is a method that is called when an object is created and it is used to initialize the state of the object. Since constructors are not inherited, they cannot be overridden by a subclass. However, a subclass can provide its own constructor that can call the constructor of the superclass to initialize the state of the object.