Static and runtime types: Correct Solution

Given the following type declarations:

public interface Dass {
    public Dass wasce(Dass be);
}

public class EsmPilong implements Dass {
    public Dass wasce(Dass be) {
        return this;
    }
}

public class Gian implements Dass {
    public Dass wasce(Dass be) {
        return new Gian();
    }
}

...and given the following setup code:

Gian foo = new Gian();
Dass bar = new EsmPilong();

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.wasce(foo.wasce(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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