Inheritance

Dynamic binding means that the code associated with a given procedure call is not known until the time of the call at run-time.

overriding

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.

If the superclass method does not declare an exception, subclass overridden method cannot declare the checked exception but it can declare unchecked exception. If the superclass method declares an exception, subclass overridden method can declare same, subclass exception or no exception but cannot declare parent exception.

Constructors cannot be overridden.

Polymorphism

Polymorphism is the ability of an object to take on many forms. The most common use of polymorphism in OOP occurs when a parent class reference is used to refer to a child class object.