Collections.sort() and Generics?

I'm getting a warning when calling collections.sort() when passing an ArrayList
containing instances of subclasses of an abstract class.

Code:

---


import java.lang.Comparable;

public abstract class Person<V extends Comparable> implements Comparable<V>  {

        public String name = "";
        public int age = 0;

        public Person() {

        }

        public int compareTo(V o) {
                return this.age - o.age;
        }

} // Person

---

Code:

---

public class Drunk extends Person {

        public double BAC = 0;

        public Drunk() {
                super();
        }

} // Drunk

---

Code:

---



import java.lang.Comparable;
import java.util.ArrayList;
import java.util.Collections;


public class GenericsTest {

        public static void main(String[] args) {

                ArrayList<Person> ppl = new ArrayList<Person>();

                Drunk myDrunk1 = new Drunk();

                Drunk myDrunk2 = new Drunk();


                ppl.add(myDrunk1);
                ppl.add(myDrunk2);

                Collections.sort(ppl);
        }

} // GenericsTest

---

Produces the warning: warning: [unchecked] unchecked method invocation: <T>sort(java.util.List<T>) in java.util.Collections is applied to (java.util.ArrayList<Person>)
Collections.sort(ppl);
^

I think there is something wrong with the way I'm declaring the abstract class Person.

Person shouldn't be generic in the first place. It should just be

Code:

---

class Person implements Comparable<Person>
...
public int compareTo(Person o)
...

---

Then see if the problem persists.

Hrm... that makes much more sense. It seems I need to re-read a chapter or two :P