Java: Type safety - unchecked cast

Question

Here is my code:

Object[] data = GeneComparison.readData(files);
MyGenome genome = (MyGenome) data[0];
LinkedList<Species> breeds = (LinkedList<Species>) data[1];

It gives this warning for the LinkedList:

Type safety: Unchecked cast from Object to LinkedList<Species>

Why does it complain about the linked list and not MyGenome?

Answer 1

Because here:

MyGenome genome = (MyGenome) data[0];

You are not using generics

And here

LinkedList<Species> breeds = (LinkedList<Species>) data[1];

You are using them.

That's just a warning, you are mixing types in the data array. If you know what are you doing ( I mean, if the second element do contains a LinkedList ) you can ignore the warning.

But better would be to have an object like this:

class Anything {
    private Object [] data;
    public Anything( Object [] data ) {
         this.data = data;
    }
    public Gnome getGnome() {
    .....
    }
    public List<Species> getBreeds() {
    ......
    }
 }

And have to methods returning proper things, prior to a correct conversion so you end up with:

Anything anything = new Anything( GeneComparison.readData(files) );
MyGenome genome             = anything.getGnome(); // similar to data[0]
LinkedList<Species> breeds = anything.getBreeds(); // similar to data[1];

Inside those methods you have to do proper transformations.