Question

1 Suppose you are designing a set of classes intended to represent a solar system and the planets and comets within it.

Which of the following class structures is a correct representation?

 public class Comet {
        ...
    }

    public class Planet {
        ...
    }

    public class SolarSystem extends Planet {
        ArrayList <Comet> comets;
    ...
    }

public class Planet {
        ...
    }

    public class Comet {
        ...
    }

    public class SolarSystem {
        ArrayList <Planet> planets;
        ArrayList <Comet> comets;
           ...
    }

 public class Comet {
        ...
    }

    public class SolarSystem extends Planet {
        ...
    }

    public class Planet {
        ArrayList <Comet> comets;
        ArrayList <SolarSystem> system;
        ...
    }

public class SolarSystem {
        ...
    }

    public class Planet extends SolarSystem {
        ...
    }

    public class Comet extends SolarSystem {
        ...
    }

public class SolarSystem {
    ...
    }

    public class Planet extends SolarSystem {
        ...
    }

    public class Comet extends Planet {
        ...
    }

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Question 21 pts

Consider the following classes.

    public abstract class Insect {
        public void move() {
            ...
        }
        
        ...
    }

    public class Butterfly extends Insect {
        public void move() {
            super.move();
            ...
        }
        ...
    }

Which of the following is a true statement?

The code works as intended.

The code will not compile because Insect is abstract.

The code will not compile because super can only be used in the constructor.

The code will not work because of infinite recursion.

The code will not compile because the super.move() should be this.move().

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Question 31 pts

The following code is intended to test if x and y are equal.

    int x = 2;
    int y = 2;
     
    if (x = y) {
        x++;
    }

Which of the following best describes why the code will not run?

It does not run as intended due to a logic error.

The code runs as intended.

It does not run as intended due to roundoff error.

It does not run as intended due to a run time error.

It does not run as intended due to a compile time error.

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Question 41 pts

Consider the following code.

    interface Vehicle {
        public int getNumWheels();
    }

    public class Scooter implements Vehicle {
        int numWheels;

        public Scooter (int w) {
            numWheels = w;
        }
        ...
    }

For a variable of the class Scooter to be instantiated which of the following must be true?

Scooter must implement a method called getNumWheels.

Scooter must have a default constructor Scooter().

Nothing, Scooter can be instantiated with no changes.

Vehicle must implement a method called getNumWheels.

Scooter must call the constructor in Vehicle.

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Question 51 pts

Consider the following code segment.

    int x = 15;
    int y = 0;
    if (y != 0 && x / y > .5) {
        ...
    }

Which of the following describes the behavior of the code?

Due to short circuit evaluation the x/y > .5 is never reached.

The code will trigger a compile time possible loss of precision error.

Precedence rules mean the x / y is never reached.

Because the x and y are ints the x / y will return a 0, making the if false.

The code will trigger a Divide by Zero ArithmeticException when the code is run.

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Question 61 pts

A cow is an animal, and a farm houses many animals including cows.

Which of the following would be an appropriate set of classes?

public class Animal extends Cow {
        /* code not shown */
    }

    public class Farm {
        ArrayList <Cow> farmAnimals;
        /* code not shown */
    }

 public class Cow extends Animal {
        /* code not shown */
    }

    public class Farm {
        ArrayList <Animal> farmAnimals;
        /* code not shown */
    }

 public class Cow extends Farm {
        /* code not shown */
    }

    public class Animal {
        ArrayList <Cow> farmAnimals;
        /* code not shown */
    }

public class Cow {
        /* code not shown */
    }

    public class Farm extends Animal {
        ArrayList <Cow> farmAnimals;
        /* code not shown */
    }

 public class Cow extends Animal {
        /* code not shown */
    }

    public class Farm {
        ArrayList <Cow> farmAnimals;
        /* code not shown */
    }

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Question 71 pts

The following code is intended to test if x and y are equal.

    int x = 2;
    int y = 2;
      
    if (x != y) {
        x++;
    }

Which of the following best describes why the code will not run as intended?

It does not run as intended due to a run time error.

It does not run as intended due to a logic error.

It does not run as intended due to a compile time error.

It does not run as intended due to roundoff error.

The code runs as intended.

Answer 1

1)

public class Planet {
        ...
    }

    public class Comet {
        ...
    }

    public class SolarSystem {
        ArrayList <Planet> planets;
        ArrayList <Comet> comets;
           ...
    }

___________________________

21)

The code works as intended.

___________________________

31)

It does not run as intended due to a compile time error.

___________________________

41)

Ans) Scooter must implement a method called getNumWheels.

___________________________

51)

Ans) Due to short circuit evaluation the x/y > .5 is never reached.

___________________________

61)

Ans)

 public class Cow extends Animal {
        /* code not shown */
    }

    public class Farm {
        ArrayList <Animal> farmAnimals;
        /* code not shown */
    }

__________________________

71)

Ans) It does not run as intended due to a logic error.

_________________________Thank You