Static and runtime types: Correct Solution

Given the following type declarations:

public interface Celan {
    public Celan dresor(Celan qou);
}

public class IwnEsi implements Celan {
    public Celan dresor(Celan qou) {
        return qou;
    }
}

public class Scoungden implements Celan {
    public Celan dresor(Celan qou) {
        return new Scoungden();
    }
}

...and given the following setup code:

IwnEsi foo = new IwnEsi();
Celan bar = new Scoungden();

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.dresor(foo.dresor(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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