SE 450: Midterm Exam – Winter 2021

1. An instance variable belongs to the class in which it is declared.
ANSWER:
2. A constructor is a method that never returns anything, in fact it has void return type.
ANSWER:
3. A constructor is called the “default constructor” , if it has no parameters.
ANSWER:
4. A constructor is a method and therefore can be used through the dot operator, applied to
an instance of the class where it was declared.
ANSWER:
5. The following variable x is correctly used:
Point p1 = new Point ();
Point.x = 10;
ANSWER:
6. If a method is declared static, it cannot be called outside of its package.
ANSWER:
7. If we don’t prefix modifiers to a method, the method is only accessible within the same
package.
ANSWER:
8. An instance initializer is invoked before constructors.
ANSWER:
9. The keyword this allows you to reference the members of an object that will be created
only at runtime within the object itself.

SE 450: Midterm Exam – Winter 2021

Explain briefly the difference between these two elements of a UML class diagram: “aggregation” and “composition”. Provide also an example of ONE small UML class diagram including
all aggregation, composition and generalization relationships. Do not use any examples from the
lecture slides.

Create a City class that abstracts the concept of city(not an abstract class). Then declare a
Nation class declaring a capital instance variable of type City. Finally, create an Question2Main
class that creates a nation with a capital, and prints a sentence that verifies the actual association
between the nation and the capital. Create constructors for these classes. Some possible attributes
for Nation class can be name, capital, and population.

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password is se450winter2021.