What does instanceof do?

The function of instanceof is to determine whether an object is an instance of a certain class, or whether it implements a certain interface. instanceof is an operator used to check whether an object is of a specified type. Usage scenarios of instanceof operator: 1. Type checking: can be used to determine the specific type of an object, so as to perform different logic according to different types; 2. Interface judgment: can be used to determine whether an object implements an interface, so as to determine whether an object implements an interface. The definition of the interface calls the corresponding method; 3. Downward transformation, etc.

Operating system for this tutorial: Windows 10 system, Dell G3 computer.

instanceof is an operator used to check whether an object is of a specified type. Its function is to determine whether an object is an instance of a certain class, or whether it implements a certain interface.

The syntax of the instanceof operator is as follows:

object instanceof Type

Among them, object is the object to be checked, and Type is the type to be checked. The expression evaluates to true if object is an instance of type Type or if object implements the Type interface; otherwise, it evaluates to false.

The instanceof operator is often used in the following scenarios:

Type checking: It can be used to determine the specific type of an object so that different logic can be executed based on different types.

Interface judgment: It can be used to judge whether an object implements an interface, so that the corresponding method can be called according to the definition of the interface.

Downcasting: When using inheritance and polymorphism, you can use the instanceof operator to check the actual type of the object pointed to by a parent class reference, and then perform the corresponding type conversion.

It should be noted that try to avoid abusing the instanceof operator. Excessive type checking may lead to reduced code complexity and maintainability. In a well-designed object-oriented program, priority should be given to using features such as polymorphism and interfaces to avoid frequent use of the instanceof operator.

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