Java Overriding - Java

What is Java Overriding?

Inside the previous chapter, we pointed out super classes and subclasses. If a class inherits away from its superclass, then there may be a chance to override the method provided that it is not marked final.

The benefit of overriding is the ability to define a behavior it truly is unique to the subclass type, which means that a subclass can implement a parent class method based totally on its requirement.

In object-orientated terms, overriding means to override the functionality of an existing method.

Instance

Allow us to study an instance.

This will produce the following result −

Output

Within the above example, you could see that even though b is a kind of Animal it runs the move method in the dog class. The reason for this is: In compile time, the test is made at the reference type. However, inside the runtime, JVM figures out the item kind and would run the technique that belongs to that precise object.

Consequently, inside the above instance, the program will collect properly since Animal class has the method move. Then, at the runtime, it runs the approach specific for that object.

Keep in mind the following example –

Example

This will produce the following result −

Output

This program will throw a compile time error since b's reference type Animal doesn't have a method by the name of bark.

Rules for Method Overriding

  • The argument list should be exactly the same as that of the overridden method.
  • The return type should be the same or a subtype of the return type declared in the original overridden method in the superclass.
  • The access level cannot be more restrictive than the overridden method's access level. For example: If the superclass method is declared public then the overridding method in the sub class cannot be either private or protected.
  • Instance methods can be overridden only if they are inherited by the subclass.
  • A method declared final cannot be overridden.
  • A method declared static cannot be overridden but can be re-declared.
  • If a method cannot be inherited, then it cannot be overridden.
  • A subclass within the same package as the instance's superclass can override any superclass method that is not declared private or final.
  • A subclass in a different package can only override the non-final methods declared public or protected.
  • An overriding method can throw any uncheck exceptions, regardless of whether the overridden method throws exceptions or not. However, the overriding method should not throw checked exceptions that are new or broader than the ones declared by the overridden method. The overriding method can throw narrower or fewer exceptions than the overridden method.
  • Constructors cannot be overridden.

Using the super Keyword

When invoking a superclass version of an overridden method the super keyword is used.

Example

This will produce the following result −

Output

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