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Today, I would like to share with you the relevant knowledge points about how to use the Instanceof keyword of Java. The content is detailed and the logic is clear. I believe most people still know too much about this, so share this article for your reference. I hope you can get something after reading this article. Let's take a look.

For example:

Class A {

Public void eat () {

System.out.println ("parent class An eats")

}

}

Class B extends A {

Public void eat () {

System.out.println ("subcategory B eating")

}

}

Class C extends A {

Public void eat () {

System.out.println ("subclass C eating")

}

}

Public class Shiyan {

Public static void main (String [] args) {

/ / TODO Auto-generated method stub

An a=new B (); / / upward transformation, assigning the instantiation of class B to the object of class A.

A.eat (); / / call the eat method of class B through the object of class A

The function of the / / an instanceof A keyword is to determine whether an instantiated object of class A can be assigned to object a.

C c = (C) a bank / uses a cast to force an instantiated object of class B into an instantiated object of C. The compiler can compile, but the runtime reports an error with a conversion exception.

A.eat ()

}

Run without the Instanceof keyword as follows:

The compiler reported a type conversion exception

Subcategory B eats.

Exception in thread "main" java.lang.ClassCastException: class polymorphism.B cannot be cast to class polymorphism.C (polymorphism.B and polymorphism.C are in unnamed module of loader 'app')

At polymorphism.Shiyan.main (Shiyan.java:28)

Improved use of the keyword Instanceof code:

At this time, the keyword Instanceof is used to determine whether the conversion is successful.

Class A {

Public void eat () {

System.out.println ("parent class An eats")

}

}

Class B extends A {

Public void eat () {

System.out.println ("subcategory B eating")

}

}

Class C extends A {

Public void eat () {

System.out.println ("subclass C eating")

}

}

Public class Shiyan {

Public static void main (String [] args) {

/ / TODO Auto-generated method stub

An a=new B (); / / upward transformation, assigning the instantiation of class B to the object of class A.

A.eat (); / / call the eat method of class B through the object of class A

The function of the / / an instanceof A keyword is to determine whether an instantiated object of class A can be assigned to object a.

Boolean isturue=an instanceof C

System.out.println (isturue)

}

The result of the improved operation:

Subcategory B eats.

False above is all the content of this article entitled "how to use Java's Instanceof keyword". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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