using `instanceof`with an "object" parameter

[Clay Chow]

For the below code, I get the following errors:


inconvertible types
found: Object
required: Fruit
if (o instanceof Fruit)
Fruit a (Fruit) a


I am using a java/javac version 1.6. Any idea why this is not working for my compiler ? I assume it should work because all classes inherit from Object. I thought it was referring to the wrong Object class, so I changed the method to public boolean add(java.lang.Object o), which seems to work.

 import java.util.*;
import static java.lang.System.out;
class Fruit {
String name;
public String toString() { return name;}
Fruit(String a) { name = a;}
}
class Apple extends Fruit {
Apple(String a) {super(a);}
}
class Group extends HashSet<Fruit> {
public static void main(String... asdf) {
Group g = new Group();
g.add(new Fruit("Fruit1"));
g.add(new Fruit("Fruit2"));
g.add(new Fruit("Fruit1"));
g.add(new Apple("Apple1"));
}
public boolean add(Object o) {
if (o instanceof Fruit) {
Fruit a = (Fruit) o;
return super.add(a);
}
return false;
//return super.add(o);
}
} 

[Henry Wong]

 

I thought it was referring to the wrong Object class, so I changed the method to public boolean add(java.lang.Object o), which seems to work.

Well, do you happen to have you own Object class, that is in the same package?

Henry

[Clay Chow]

Definitely do not.
Did not make one and

Made sure there are none in the directory and program is not linked to any package.

From the java API i see there's another Object interface, org.omg.CORBA
Interface Object.

[Henry Wong]

 

From the java API i see there's another Object interface, org.omg.CORBA Interface Object.

But unless you "import" that Object, it wouldn't be an issue. This is why I asked if you had an Object in your package, because the current package (just like java.lang) does not need to be imported.

Henry