Overrides vs overloads of methods

Method rewrite （​​override​​）

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2. Method rewrite
   Subclasses inherit methods from their parent classes , Sometimes , The subclass needs to modify the implementation of the method defined in the parent class , This is called ​ Method rewrite ​(​​method overriding​​).“ rewrite ” The concept of “ heavy load ” be similar , They are ​​Java​​“ polymorphic ” One of the techniques , So-called “ heavy load ”, That is, the method name is the same , But you can do different things on different occasions . When a subclass inherits a parent , And the names of the methods in the subclass and the methods in the superclass 、 When the number and type of parameters are identical , This method in the subclass is said to override the method in the superclass .“ rewrite ” Also known as “ make carbon copies ”、“ Cover ”.
   
3. How to use rewrite
   ​​classSuper{ Access right Method return value type Method 1（ Parameters 1） {...}}classSubextendsSuper{ Access right Method return value type Method 1（ Parameters 1） —————> Duplicate methods in the parent class {...}} ​​
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Be careful ： Method rewriting must follow two principles , Otherwise, the compiler will point out the program error .

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• Overridden methods cannot have more strict access than overridden methods ;
• Overridden methods cannot generate more exceptions than overridden methods （ About anomalies , I'll introduce it later ）.
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Method overloading （​​overload​​）

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2. Method overloading
   First, let's review the method overloading mentioned earlier ,​ Method overloading ​ Multiple methods can have the same name , however ​ The number or type of parameters cannot be exactly the same ​. When calling a method , The compiler determines the method currently used according to the number and type of parameters . Method overloading brings convenience to programming , yes ​​OOP​​ The concrete realization of polymorphism . stay ​​Java​​ In the class library of the system , Overloading many important methods , It provides convenience for users to use these methods .
   
3. Overloaded rules

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• The overloaded method must change the parameter list ( The number or type of parameters is different );
• 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 .
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