Example of equivalence code of instanceof and Class in java

This article mainly studies the equivalence of instanceof and Class in Java, as follows.

The instanceof operator in java is used to indicate whether an object is an instance of a specific class at runtime. instanceof indicates whether the object is an instance of this particular class or a subclass by returning a boolean value.

Example 1 (instanceof)

Interface Person

 public interface Person {public void eat();}

Implement People class

 public class People implements Person {private int a=0; @Override public void eat() { System.out.println("======="+a); }}

Subclass xiaoming:

 public class xiaoming extends People {private String name;@Overridepublic void eat() { System.out.println("++++++++++");}}

Main function

 public static void main(String[] args) { People p=new People(); xiaoming x=new xiaoming(); System.out.println(p instanceof Person); System.out.println(p instanceof xiaoming); -----2 System.out.println(x instanceof Person); System.out.println(x instanceof People); }

Note: The code in the above 2 will not report errors during compilation.

Running results:

 truefalsettrue

Example 2

 package com.test.class_obj;class Base {}class Derived extends Base {}public class FamilyVsExactType {static void test(Object x) {System.out.println("Testing x of type " + x.getClass().getSimpleName());System.out.println("---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Base));System.out.println("x instanceof Derived " + (x instanceof Derived));System.out.println("----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Derived.class.isInstance(x));System.out.println("----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- (x.getClass().equals(Base.class)));System.out.println("x.getClass().equals(Derived.class)) " + (x.getClass().equals(Derived.class)));System.out.println("************************************************");System.out.println("******************************************************");}public static void main(String[] args) {test(new Base());test(new Derived());}}

The output content is as follows:

 Testing x of type Base------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- false*********************************************************************************Testing x of type Derived------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Base.class falsesex.getClass() == Derived.class trueex.getClass().equals(Base.class)) falsesex.getClass().equals(Derived.class)) true********************************************************************************************************************************************************************************************************************************* Process finished with exit code 0

Through the above tests, the following conclusions can be drawn:

• The result generated by instanceof() and isInstance() are the same
• The same result generated by equals() and ==
• The parent class can be an instance of a child class, but the child class cannot be an instance of a parent class.
• Inheritance is not considered when comparing Class objects

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