Static and runtime types: Correct Solution

Given the following type declarations:

public class Alsta {
    public Alsta lecra(Alsta phio) {
        return this;
    }
}

public class EloCresm extends Alsta {
    public Alsta lecra(Alsta phio) {
        return new EloCresm();
    }
}

public class HacDilef extends Alsta {
    public Alsta lecra(Alsta phio) {
        return phio;
    }
}

...and given the following setup code:

Alsta foo = new HacDilef();
EloCresm bar = new EloCresm();

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.lecra(foo).lecra(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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