Java generics bounded types with list

[LongBigBronzeElephantFish]

I got a small problem here regarding generics bounded type with lists. Please help out!

Model.java
public class Model {
}

SubModel.java
public class SubModel extends Model {
}

ClassA.java
public class ClassA<T extends Model> {
private List<T> models;

public ClassA() {
List<T>.add((T) new Model());
}

public List<T> getModels() {
return models;
}
}

It gives me an unchecked cast from Model to T warning on this line:
List<T>.add((T) new Model());

I understand I'm getting this warning because all I can safely cast from a sub class into a super class but not the other way round.

Is there any way to get over this problem or can I just safely supress the warning?

Thanks!

 

[davidktw]

I got a small problem here regarding generics bounded type with lists. Please help out!

Model.java
public class Model {
}

SubModel.java
public class SubModel extends Model {
}

ClassA.java
public class ClassA<T extends Model> {
private List<T> models;

public ClassA() {
List<T>.add((T) new Model());
}

public List<T> getModels() {
return models;
}
}

It gives me an unchecked cast from Model to T warning on this line:
List<T>.add((T) new Model());

I understand I'm getting this warning because all I can safely cast from a sub class into a super class but not the other way round.

Is there any way to get over this problem or can I just safely supress the warning?

Thanks!

It means you are most likely working it wrongly in this case. If you are already using generics, you should try and avoid casting as much as possible.

Without considering generics, the following statement is wrong isn't it ?

List<T>.add((T) new Model());

//Removing generics becomes
List.add(...)

What is List ? It's a type, are you calling a static method of List ?
I would believe it should be

models.add(...)

In your generics, your hint is "T extends Model" hence you are saying that type "T" is a subclass of type "Model". When you instantiate an object from the Model class/type, how can you say it MUST be of type "T" ?

If it is not of type "T", how can you push into a list that you have declared to only contain objects of type "T" and nothing but type "T" in this statement ?

private List<T> models;

Your code doesn't make sense, please read the one below.

class Model {
}

public class ClassA<T extends Model> {
    private List<T> models;

    public ClassA() {
    }

    public List<T> getModels() {
        return models;
    }

    public void add(T model) {
      models.add(model);
    }
}