Static and runtime types: Correct Solution

Given the following type declarations:

public class Umbes {
    public Umbes stiZeja(Umbes ner) {
        return ner;
    }
}

public class Ofin extends Umbes {
    public Umbes stiZeja(Umbes ner) {
        return new Ofin();
    }
}

public class Gomit extends Umbes {
    public Umbes stiZeja(Umbes ner) {
        return this;
    }
}

...and given the following setup code:

Umbes foo = new Gomit();
Umbes bar = new Ofin();

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.stiZeja(foo.stiZeja(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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