STUDENT DATA:

• NAME: _______FEDOR ANDRIANOV_______

• ID#: _____________________________________

• SECTION#: ________________________________

1. (20 points):

Fill in the blanks in each of the following:

• Operator ____instanceof____ determines whether its first operand is an instance of its second operand.
• In order to support java.lang.Object.clone() method, an object should implement ____Cloneable ____ interface.
• The ____Object____ class is the top of the class hierarchy. All classes are descendants from this class and inherit methods from it.
• A class member that is not declared as ____static____ is implicitly an instance member.
• You can prevent a class from being subclassed by using the ____final____ keyword.

2. (20 points):

The following program contains several bugs. Please find and fix them.

    public class SomethingIsWrong {
	public interface anInterface {
	    void aMethod(int aValue) { System.out.println("Hi Mom"); }
	}
	public static void main(String[] args) {
	    StringBuffer[] stringBuffers = new StringBuffer[10];
	    for (int i = 0; i < stringBuffers.length; i++) {
		stringBuffers[i].append("String Buffer at index " + i);
	    }
	}
    }

Please write your answer on the other side of page 1 --->

    public class SomethingIsWrong {
	public interface anInterface {
	    //interface should not implement any methods
	    void aMethod(int aValue);
	}
	public static void main(String[] args) {
	    StringBuffer[] stringBuffers = new StringBuffer[10];
	    for (int i = 0; i < stringBuffers.length; i++) {
		//array elements should be created before they can be used
		stringBuffers[i] = new StringBuffer();
		stringBuffers[i].append("String Buffer at index " + i);
	    }
	}
    }

3. (20 points):

Answer the following questions:

• What is the value of the following expression and why?

  	new Integer(1).equals(new Long(1))

• Is the following code legal?

  	try {
  	    // do something
  	} finally {
  	    // do something
  	}
  	

• What is wrong with using the following type of exception handler?

  	catch (Exception e) {
  	    // do something
  	}
  	

• What is the value of i after the following code snippet executes?

  	int i = 17; i >>= 2; i = i++%5;

Answers:

• The value is false (of type boolean). Although numerical values of new Integer(1) and new Long(1) are the same, but these quantities are of different types, and therefore are considered not equal.
  
  
• Yes, one can have zero catch statements after a try statement as long as there is a finally statement.
  
  
• This exception handler is too general, and therefore not very useful. In order to handle in a meaningful way various exceptions caught by this handler, programmer has to create an unnecessary complicated handling routine. Still the handler can catch even more then programmer anticipated, so one most likely will end up with a generic error message which is not very helpful in practice.
  
  
• The answer is 4

  	int i = 17;		//i is 17
  	i >>= 2;		//i is 17/4 which is 4
  	i = i++%5;		//i is 4%5 which is 4
  	

4. (20 points):

Suppose that you have written a time server, which periodically notifies its clients of the current date and time. Write an interface that the server could use to enforce a particular protocol on its clients. Please write your answer on the other side of page 2 --->

    public interface TimeWatcher {
	public void setTime(int h, int m, int s);
	public void setDate(int mo, int d, int y);
    }

5. (20 points):

Create a program that reads an unspecified number of integer arguments from the command line and adds them together. For example, suppose that you enter the following:

    java Adder 1 3 2 10 

The program should display 16 and exit. In addition, your program should catch and handle all exceptions that might arise because of a bad input. Each type of exception should be handled independently, by printing an appropriate error message which would specify what exactly was wrong with the input. Hint: to convert a string representing an integral number into an integer, you can use method

    public static int java.lang.Integer.parseInt(String s)
	    throws NumberFormatException 

    public class Adder {
	public static void main(String[] args) {

	    try {
		int sum = Integer.parseInt(args[0]);
		for (int i = 1; i < args.length; i++) {
		    sum += Integer.parseInt(args[i]);
		}
		System.out.println("The sum is " + sum);

	    } catch (NumberFormatException ex) {
		System.out.println("Please enter only integral arguments.");

	    } catch (ArrayIndexOutOfBoundsException ex) {
		System.out.println("Please enter one or more integral arguments.");
	    }
	}
    }

Good Luck !