The difference between overloading and rewriting
 

One 、 heavy load

heavy load (overloading) It's in a class , The method name is the same , And the parameters are different . The return type can be the same or different .

Every overloaded method （ Or constructors ） There must be a unique list of parameter types .

The most common place is the overloading of construction methods .

Overloads are in the same class with the same method name , Different parameters （ Number , type , The order ） Definition of the method of ,
Construction method common method , Abstract methods can be overloaded ; Rewriting is when a subclass inherits from its parent class ,
The method overridden in the subclass must be exactly the same as the parent method , It can be used @override Check whether it is an override method

Overload rule :

• The overloaded method must change the parameter list ( Number of parameters , Different type or order );
• Overloaded methods can change the return type ;
• Overloaded methods can change access modifiers ;
• Overloaded methods can declare new or broader check exceptions ;
• Methods can be overloaded in the same class or in a subclass .
• Cannot use return value type as distinguished standard of overloaded function .

Two 、 rewrite

Rewriting is a subclass's rewriting of the implementation process of the parent's accessible methods , Neither the return value nor the parameter can be changed . That is, the shell remains the same , Core rewrite ！

The advantage of overriding is that subclasses can be as needed , Define your own actions . That is to say, the subclass can implement the methods of the parent class as required .

An overriding method cannot throw a new check exception or an exception that is broader than the overriding method declaration . for example ： A method of the parent class declares a check exception IOException, But when overriding this method, it cannot be thrown Exception abnormal , because Exception yes IOException Parent class of , Throw out IOException Abnormal or IOException Subclass exception of .

In the object-oriented principle , Overriding means that you can override any existing method

3、 ... and 、 The difference between overloading and rewriting

Method rewrite (Overriding) And overloading (Overloading) yes java Different manifestations of polymorphism , Rewriting is a manifestation of polymorphism between parents and children , Overloading can be understood as a concrete manifestation of polymorphism .

• (1) Method overloading is defined in a class with more than one method with the same name , The number of parameters is different or the number is the same, but the type and order are different , It's called method overloading (Overloading).
• (2) Method rewriting is when a subclass has a method with the same name as the parent's method , And the number of parameters is the same as the type , The return value is the same way , It's called rewriting (Overriding).
• (3) Method overloading is a polymorphic representation of a class , Method rewriting is a kind of polymorphism between subclass and parent class .