instanceof Vs getClass( )

Question

I see gain in performance when using getClass() and == operator over instanceOf operator.

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Answer 1

getClass() has the restriction that objects are only equal to other objects of the same class, the same run time type, as illustrated in the output of below code:

class ParentClass{
}
public class SubClass extends ParentClass{
    public static void main(String []args){
        ParentClass parentClassInstance = new ParentClass();
        SubClass subClassInstance = new SubClass();
        if(subClassInstance instanceof ParentClass){
            System.out.println("SubClass extends ParentClass. subClassInstance is instanceof ParentClass");
        }
        if(subClassInstance.getClass() != parentClassInstance.getClass()){
            System.out.println("Different getClass() return results with subClassInstance and parentClassInstance ");
        }
    }
}

Outputs:

SubClass extends ParentClass. subClassInstance is instanceof ParentClass.

Different getClass() return results with subClassInstance and parentClassInstance.