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This article mainly explains the "detailed explanation of the reasons why java can not inherit more". The content of the explanation in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "detailed explanation of the reasons why java can not inherit more".

Multiple inheritance means that a subclass can inherit from multiple parent classes at the same time, so it has the characteristics of multiple parent classes at the same time, but the disadvantage is significant.

1. If the subclass inherits the same member variable in the parent class, the subclass will not be able to tell which parent's member variable to use when referencing the variable.

Such as:

Public class classA / / parent classA {private int num = 0;} public class classB / / parent classB {private int num = 1;} public class classC extends classA,classB / / subclass classC inherits from classA and classB {public static void main (String [] args) {classC obj = new classC (); obj.print (); / / calls the parent member variable num, so num equals 0 or 1? } public void print () {System.out.println (super.num);}}

two。 If multiple parent classes inherited by a subclass have the same method, and the subclass does not override the method (if overridden, the method in the subclass is used directly), it will not be possible to determine which parent class's method is called when the method is called.

Such as:

Public class classA / / parent classA {public void fun () {System.out.print ("hello");}} public class classB / / parent classB {public void fun () {System.out.print ("hello");}} public class classC extends classA,classB {public static void main (String [] args) {classC t = new classC (); t.print ();} public void print () {super.fun () / / call the fun method in the parent class, but since both classA and classB have fun () methods, it will not be possible to determine which parent class method}} will be used.

Therefore, Java only allows single inheritance, that is, a subclass can only inherit from one parent class. However, in order to expand the functionality of subclasses, Java uses interfaces to overcome the shortcomings of not using multiple inheritance.

The interface is a special abstract class, the member variables in the interface default to the static final type, that is, constant, and the methods in the interface are abstract and have no method body.

The specific method can only be implemented by the class that implements the interface, and the method of the implementing class will always be called (there is no ambiguity), so there is no second disadvantage of multi-inheritance; and because the interface has only static constants, however, because static variables determine the invocation relationship at compile time, errors will be prompted at compile time even if there is a certain conflict. Referencing static variables generally uses the class name or interface name directly to avoid ambiguity, so there is no first disadvantage of multi-inheritance. These disadvantages also do not exist in the case where an interface inherits multiple parent interfaces.

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