CS 1102 Graded Quiz Chapter 4-6 with Answers- University of the People

Question 1
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Question text
Consider the following Java program. Which line implements an interface method?

import java.awt.event.*;
import javax.swing.*;
public class MouseWhisperer extends JFrame implements MouseListener
{
MouseWhisperer() {
super("COME CLOSER");
setSize(300,100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addMouseListener(this);
setVisible(true);
}
public void mouseClicked(MouseEvent e) { setTitle("OUCH"); }
public void mousePressed(MouseEvent e) { setTitle("LET GO"); }
public void mouseReleased(MouseEvent e) { setTitle("WHEW"); }
public void mouseEntered(MouseEvent e) { setTitle("I SEE YOU");
}
public void mouseExited(MouseEvent e) { setTitle("COME
CLOSER"); }
public static void main(String[] args) { new
MouseWhisperer(); }
}

Select one:
a. public void mouseEntered(MouseEvent e) { setTitle("I SEE YOU"); }
b. addMouseListener(this);
c. super("COME CLOSER");
d. public class MouseWhisperer extends JFrame implements MouseListener {


e. public static void main(String[] args) { new MouseWhisperer(); }

Feedback
Your answer is incorrect.
See Section 6.3.2.

,The correct answer is: public void mouseEntered(MouseEvent e) { setTitle("I SEE YOU"); }

Question 2
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Question text
What is the output of the following Java program?
public class Food {
static int count;
private String flavor = "sweet";
Food(String s) { flavor = s; }
void setFlavor(String s) { flavor = s; }
String getFlavor() { return flavor; }
static public void main(String[] args) {
Food pepper = new Food("spicy");
Food chile = pepper;
pepper.setFlavor("smoky");
System.out.println(chile.getFlavor());
}
}

Select one:
a. spicy
b. false
c. true
d. smoky


e. sweet

Feedback
Your answer is correct.
Setting "chile = pepper" causes the two object variables to refer to the same single object. Because
"chile" and "pepper" refer to the same object, the flavor set by "pepper.setFlavor" is seen by
"chile.getFlavor". See Section 5.1.2 of Eck (2014).
The correct answer is: smoky

Question 3
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Question text
Consider the following Java program. Which one of the following does NOT describe
"MouseWhisperer"?

import java.awt.event.*;
import javax.swing.*;
public class MouseWhisperer extends JFrame implements MouseListener
{
MouseWhisperer() {
super("COME CLOSER");
setSize(300,100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addMouseListener(this);
setVisible(true);
}
public void mouseClicked(MouseEvent e) { setTitle("OUCH"); }
public void mousePressed(MouseEvent e) { setTitle("LET GO"); }
public void mouseReleased(MouseEvent e) { setTitle("WHEW"); }
public void mouseEntered(MouseEvent e) { setTitle("I SEE YOU");
}
public void mouseExited(MouseEvent e) { setTitle("COME
CLOSER"); }
public static void main(String[] args) { new
MouseWhisperer(); }
}

Select one:
a. A "MouseWhisperer" object can be assigned to a "JFrame" variable.


b. A "MouseWhisperer" object listens for action events.
c. A "MouseWhisperer" object responds to mouse movement.
d. A "MouseWhisperer" object responds to mouse clicks.
e. The "MouseWhisperer" class can be run as a program.

Feedback
Your answer is incorrect.
A "MouseWhisperer" object responds to mouse events ("addMouseListener"), not action events. See
Sections 6.1.3 and 6.3.1.