Question

I have 3 class and, first is Person :

public class Person {    
    Person() {

    }
}

Second is Engineer that extends of Person

public class Engineer extends Person { 
    Engineer() {

    } 
}

and another extends of Person

public class Doctor extends Person {
    Doctor() {

    } 
}

Last one is Work that take in constructor an object Person

public class Work {
    Work(Person p) {
    //how to insure that p is Engineer ?
    }
}

How to detect that an object p is Engeneer and not from another class ?

Answer 1

You can use the instanceof keyword for checking the type of an object. It works like this

if(p instanceof Engineer) {
   // do Engineer stuff
} else {
   // not an Engineer object
}