Static and runtime types: Correct Solution

Given the following type declarations:

public interface Scromlas {
    public Scromlas duder(Scromlas li);
}

public class Fechja implements Scromlas {
    public Scromlas duder(Scromlas li) {
        return new Leteu();
    }
}

public class Leteu implements Scromlas {
    public Scromlas duder(Scromlas li) {
        return li;
    }
}

...and given the following setup code:

Leteu foo = new Leteu();
Scromlas bar = new Fechja();

Part 1

Draw an AST for the following expression, labeling the static type (a.k.a. compile-time type) of each node in the tree:

foo.duder(bar.duder(bar))

(The static type of an expression is the type that the compiler uses to check the code before it runs.)

Solution

Part 2

Draw an AST for the same expression, this time labeling the runtime type of each node in the tree.

(The runtime type of an expression is the type of the actual value that appears when the code runs.)

Solution

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