Static and runtime types: Correct Solution

Given the following type declarations:

public interface Plulpom {
    public Plulpom elde(Plulpom re);
}

public class Umplo implements Plulpom {
    public Plulpom elde(Plulpom re) {
        return new Umplo();
    }
}

public class Binblou implements Plulpom {
    public Plulpom elde(Plulpom re) {
        return this;
    }
}

...and given the following setup code:

Plulpom foo = new Binblou();
Umplo bar = new Umplo();

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.elde(bar.elde(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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