CS 1301 Program 5 Fall 2014

Educational Goals: The educational goals of this program are that the student should get practice with:

• design with classes
• design of methods with various return types and parameters
• implement a simple sorting algorithm
• using for and while loops
• using arrays
• documentation

Problem Description:

Many problems in computer science can be solved using different algorithms, some more efficient than others. Such is the case with array sorting algorithms. In class, we discussed the bubble sort algorithm, named due to the fact that it compares adjacent numbers (or bubbles) and swaps them if not in order. Programmers want to minimize algorithm execution time (in other words, make them faster). In order to measure speed, one can run the algorithm on a given problem and measure the amount of time the algorithm took to solve it.

In this program, you will use object oriented programming techniques to design a stop watch class that will be used to measure the speed of two sorting algorithms: bubble sort (that you have to implement) and Java Standard Library's Arrays.sort() method.

You have to design the following two classes:

• stopWatch
• randomArray

The stopWatch class has two private data fields: startTime and stopTime of type long. This class has a no-arg constructor that initializes startTime and stopTime to 0. It also has three methods:

• start(), return type void, no parameters. When called, this method uses the Date object's getTime() method (from java.util.Date) to set startTime.
• stop(), return type void, no parameters. When called, this method uses the Date object's getTime() method (from java.util.Date) to set stopTime.
• getElapsedTime() return type long, returns the difference between stopTime and startTime

The randomArray class has one private data field, an array of integers. The constructor has one parameter, an integer specifying the size of the array. The constructor initializes the array and calls the method randomize() (discussed below). The randomArray class has the following methods:

• randomize(), return type void, no parameters. This method assigns every element of the array a random value between 0 and 1024.
• BubbleSort(), return type long, no parameters. This method implements the bubble sort sorting algorithm discussed in class. You have to declare, instantiate and use a stopWatch object to measure the execution time of the algorithm. This method returns the execution time.
• ArraySort(), return type long, no parameters. Here, you simply make a call to the Arrays.sort() method, measure the execution time using the stopWatch and return it.
• isSorted(), return type boolean, no parameters. This function returns true if the array is sorted, otherwise returns false.

The main class (program5) is given and you CANNOT change it.

public class program5 {
   public static void main(String[] args)
   {
      Scanner s = new Scanner(System.in); // declare and instantiate scanner object
      System.out.print("Please enter number of elements in array: "); // prompt user for nr of elements
      int nrElements = s.nextInt();

      System.out.println("Now creating the random array object...");
      randomArray r = new randomArray(nrElements); // declare and instantiate randomArray object
      
      System.out.println("The return value of RandomArray's .isSorted() method now is: " + r.isSorted());
      
      System.out.println("Now sorting using bubble sort...");

      long bsTime = r.BubbleSort(); // run BubbleSort algorithm
      System.out.println("The return value of RandomArray's .isSorted() method now is: " + r.isSorted());

      System.out.println("Bubble sort algorithm took: " + bsTime + " milliseconds to complete");

      System.out.println("Randomizing array...");
      r.randomize();
      System.out.println("The return value of RandomArray's .isSorted() method now is: " + r.isSorted());
      
      System.out.println("Now sorting using Java Standard Libraries .ArraySort() method ...");
      long asTime = r.ArraySort(); // run Java's ArraySort algorithm
      System.out.println("The return value of RandomArray's .isSorted() method now is: " + r.isSorted());
      System.out.println("Arrays.sort algorithm took: " + asTime + " milliseconds to complete");
   }
}

Sample interaction with the program (please note that your execution times may vary due to computer hardware and other processes open):

Sample run 1: 

Please enter number of elements in array: 1000
Now creating the random array object...
The return value of RandomArray's .isSorted() method now is: false
Now sorting using bubble sort...
The return value of RandomArray's .isSorted() method now is: true
Bubble sort algorithm took: 9 milliseconds to complete
Randomizing array...
The return value of RandomArray's .isSorted() method now is: false
Now sorting using Java Standard Libraries .ArraySort() method ...
The return value of RandomArray's .isSorted() method now is: true
Arrays.sort algorithm took: 1 milliseconds to complete




Sample run 2:

Please enter number of elements in array: 10000
Now creating the random array object...
The return value of RandomArray's .isSorted() method now is: false
Now sorting using bubble sort...
The return value of RandomArray's .isSorted() method now is: true
Bubble sort algorithm took: 128 milliseconds to complete
Randomizing array...
The return value of RandomArray's .isSorted() method now is: false
Now sorting using Java Standard Libraries .ArraySort() method ...
The return value of RandomArray's .isSorted() method now is: true
Arrays.sort algorithm took: 3 milliseconds to complete




Sample run 3:

Please enter number of elements in array: 100000
Now creating the random array object...
The return value of RandomArray's .isSorted() method now is: false
Now sorting using bubble sort...
The return value of RandomArray's .isSorted() method now is: true
Bubble sort algorithm took: 16468 milliseconds to complete
Randomizing array...
The return value of RandomArray's .isSorted() method now is: false
Now sorting using Java Standard Libraries .ArraySort() method ...
The return value of RandomArray's .isSorted() method now is: true
Arrays.sort algorithm took: 10 milliseconds to complete

Notes:

• When you test your program, make sure the BubbleSort method works correctly, checked by the isSorted method's return value.

Implement the design

There are several specifications about how your program should be written.

• you need to use counters and loops
• make sure you format the lines of the output as described. The line breaks and the punctuation should be as shown. The output messages should be exactly as given.

Please read the documentation standard on the class web page. As you can see from looking at the grading criteria, we will be looking to see how you meet these standards. Note particularly that we require a prolog!

Remember that the program must run with NO errors or warnings. If it does not, it will not be graded!