Quiz 9

Friday

With a piece of paper, write down your name and answers to the following questions.

1. What is an interface?

   1. An interface is a collection of public methods.
   2. An interface is a collection of interactive graphic components.
   3. An interface is a collection of method definitions and constants.
   4. An interface is a class that serves as the superclass of other classes.

2. What will the following program print?

   import java.util.StringTokenizer;
   
   public class Program {
   	public static void main(String[] args) {
   		String str = "one#two@three";
   		StringTokenizer strTokenizer = new StringTokenizer(str, "&%@#", true);
   		while (strTokenizer.hasMoreTokens())
   			System.out.println(strTokenizer.nextToken());
   	}
   }

   Answer:
       one
    #
    two
    @
    three

3. Is the following statement correct, and why?

   Every class has a toString method and an equals method inherited from the Object class.

   Answer: Yes, this statement is correct.

4. With the following class hierarchy...

   

   Is the following code correct, and why?

   public class Program {
   	public static void main(String[] args) {
   		try {
   			Scanner scanner = new Scanner(System.in);
   			int num = scanner.nextInt();
   
   		} catch (NoSuchElementException e) {
   			System.err.println("No Such Element");
   
   		} catch (InputMismatchException e) {
   			System.err.println("Input Mismatch");
   		}
   	}
   }

   Correction:

   public class Program {
   	public static void main(String[] args) {
   		try {
   			Scanner scanner = new Scanner(System.in);
   			int num = scanner.nextInt();
   
   		} catch (InputMismatchException e) {
   			System.err.println("Input Mismatch");
   
   		} catch (NoSuchElementException e) {
   			System.err.println("No Such Element");
   		}
   	}
   }

Student Performance and Statistics

A histogram of student performance on percentage grades for Quiz 9 on Friday.

A table showing the average performance for each question in Quiz 9 on Friday.