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Answer 40

Question 41

True or False? Everything in Java is passed and returned by reference.

Answer 41

Question 42

True or False? Each of the accessor methods shown in Listing 6 returns a copy of the reference pointing to either a Turtle object or a World object.

Listing 6 . Question 42.
public Turtle getJoe(){return joe;} public Turtle getSue(){return sue;}public World getMars(){return mars;}

Answer 42

Question 43

True or False? Code in the println method calls a method named toString on each incoming primitive value and displays the string value returned by that method.

Answer 43

Question 44

True or False? The toString method is overridden (not overloaded) in the World and Turtle classes so as to return a string value describing the object.

Answer 44

Question 45

True or False? The code in Listing 7 replaces the default all-white picture in a World object with another picture. (Note, the variable named mars contains a reference to an object of the class World .)

Listing 7 . Question 45.
public void run(){ mars.setPicture(new Picture("Prob01.jpg"));

Answer 45

Question 46

True or False? The background of a World object consists of an object of Ericson's Picture class. (A Picture object is encapsulated in the World object.)

Answer 46

Question 47

True or False? The code in Listing 8 uses two levels of indirection to add my name to the picture that forms thebackground of the world shown in Figure 1 .

Listing 8 . Question 47.
mars.getPicture().toString( "Dick Baldwin",10,20);

Figure 1 - Question 47.

Image of two turtles maneuvering in front of a background image.

Answer 47

Question 48

True or False? A Turtle object encapsulates many methods that can be used to manipulate the turtle in a variety of different ways.

Answer 48

Question 49

True or False? A call to the forward method of a turtle object with no parameters causes the turtle to move forward by a default distance of 100 pixels.

Answer 49

Question 50

True or False? A call to the moveTo method of a turtle object with a single parameter value of 150 causes the turtle to move forward by a distance of 150 pixels.

Answer 50

Figures

Listings

What is the meaning of the following two images?

This image was inserted here simply to insert some space between the questions and the answers to keep them from being visible on the screen at thesame time.

The image is also an example of the kinds of things that we do in my course titled ITSE 2321, Object-Oriented Programming.

Spacer image of a rabbit and a penguin.

This image was also inserted for the purpose of inserting space between the questions and the answers.

Spacer image of a penguin and some houses.

Answers

Answer 50

False. The moveTo method of the Turtle class cannot be called with a single parameter. Two parameters are required.

Back to Question 50

Answer 49

True.

Back to Question 49

Answer 48

True.

Back to Question 48

Answer 47

False. The code in Listing 8 won't compile. The toString method does not apply to images. The correct code is shown in Listing 9 .

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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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