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Class Notes

• Chapter2 Questions
• Course Home page

• 1. Consider the following statement:
• String greeting = 13;
  • Answer = B) The statement yields a compile-time error

• 2. Which of the following statements is correct?
  • Answer = A) Identifiers can be made up of letters, digits, and the underscore (_) character

• 3. it is an error to use the value of a variable that has never had a value assigned to it.
  • Answer = A) True

• 4. Which of the following code fragments will cause an error?
  • Answer = D (int luckyNumber;
  • System.out.println(luckyNumber);

• 5. The ____________ of a class specifies what you can do with its objects.
  • Answer = Public Interface

• 6. Which of the following statements is correct in the Java language?
  • Answer = C) Every object belongs to a class

• 7. Which of the folowing counts the number of characters in a string?
• String greeting = "Hello, World!";
  • Answer = A) int n = greetng.length();

• 8. A method name is _______ if a class has more than one method with that name (but different parameter types).
  • Answer = overloaded

• 9. Object variables store ______.
  • Answer = A) references

• 10. Based on the followng statement, which of the following statements sets the title of the frame?.
• JFrame frame = new JFrame();
  • Answer = D) frame.setTitle("An Empty Frame");

• 11. Use a _______ to recover the Graphics2D object from the Graphics parameter of the paintComponent method?
  • Answer = Cast

• 12. Which of the following statements would complete the code below?
• public class RectangleComponent extends JComponent
• {
  • public void paintComponent (Graphics g)
  • {
    • // Recover Graphics2D
    • Graphics2D g2 = (Graphics2D) g;

• • • //Draw a square
    • ____________
    • g2.draw(box);
  • }
• }
  • [Answer = A)Rectangle box = new Rectangle(5, 10, 20, 20);

• 13.Consider the following code fragment:
• public class RedFlagComponent
• {
  • public void paintComponent(Graphics g)
  • {
    • Graphics2D g2 = (Graphics2D) g;
    • Rectangle flag = new Rectangle(100, 100, 200, 100);
    • g2.draw(flag);
  • }
• }
  • [Answer = D) It is impossible to add a RedFlagComponent object to a frame because the class does not extend JComponent.

All answers

1. B
2. A
3. True
4. D
5. Public Interface
6. C
7. A
8. Overloaded
9. A
10. D
11. Cast
12. A
13. D