Static and runtime types: Correct Solution

Given the following type declarations:

public interface Wurie {
    public Wurie scha(Wurie nort);
}

public class Pteshe implements Wurie {
    public Wurie scha(Wurie nort) {
        return new Pteshe();
    }
}

public class Bospa implements Wurie {
    public Wurie scha(Wurie nort) {
        return nort;
    }
}

...and given the following setup code:

Bospa foo = new Bospa();
Wurie bar = new Pteshe();

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.scha(foo).scha(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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