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javainstanceofscjp

instanceof enthuware OCAJP

interface Flyer{ }  
class Bird implements Flyer { }  
class Eagle extends Bird { }  
class Bat { }  

public class TestClass {  

public static void main(String[] args) {  
    Flyer f = new Eagle();  
    Eagle e = new Eagle();  
    Bat b = new Bat();  

    if(f instanceof Flyer) System.out.println("f is a Flyer");  
    if(e instanceof Bird) System.out.println("e is a Bird");  
    if(b instanceof Bird) System.out.println("f is a Bird");  
    }  
}

This is a code sample from Enthuware. I cant figure out why the third instanceof operator ( b instanceof Bird) doesn't evaluate to false but instead give me a compile time error. P.S. -i couldn't get what Enthuware was trying to explain me

The compile time error which i got was

TestClass.java:16: error: inconvertible types

if(b instanceof Bird) System.out.println("f is a Bird"); ^

required: Bird

found: Bat

1 error

Solution

  • instanceof operator evaluates true or false only if the objects are linked via some inheritance and throws error otherwise