Static and runtime types: Correct Solution

Given the following type declarations:

public interface Holsen {
    public Holsen frec(Holsen drod);
}

public class Reng implements Holsen {
    public Holsen frec(Holsen drod) {
        return this;
    }
}

public class Screngrard implements Holsen {
    public Holsen frec(Holsen drod) {
        return drod;
    }
}

...and given the following setup code:

Holsen foo = new Reng();
Holsen bar = new Screngrard();

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.frec(bar).frec(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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