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  The difference between overloading and rewriting

  One 、 heavy load

  Two 、 rewrite

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

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The difference between overloading and rewriting
 

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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

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

Difference point	Overloading methods	Rewriting methods
parameter list	Must be modified	It must not be modified
Return type	You can modify	It must not be modified

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 .