Class Notes: Data Structures and Algorithms

Summer-C 1999 - M WRF 2nd Period CSE/E119

Instructor: M.S. Schmalz -- TAs: TA Mailing List

Project 1 Assignment -- Due Wed 2 June 1999:11.00am

• Goal. The purpose of this project is to provide basic hands-on experience with Java programming for all COP3530 students, especially those who may be new to Java. The purpose of the application is to compute and display to the screen the minimum, maximum, and mean of a sequence of numbers read from stdin. When the TAs test the program, the numbers will be piped to stdin from a text file (e.g., the command line will read

  java Proj1 < input-file

  where input-file is a text file that you enter using a word processor, and store it on disk. More information about the test procedure is posted below under Example Test Procedure.

• Features. We will be making a modular program with object-oriented design and implementation, as follows.

• Functionality. The program implemented as a Java Class called Proj1 will perform the following steps:
  Step 1. Read input from stdin (standard input stream) as a stream of integers, with spaces, newline characters, or commas between them (i.e., standard delimiters). You should implement this as a method in a class called P1Sequence.

  Hint: You might want to use a one-dimensional array class to store the input data for later processing. Array classes are described in Dr. Crummer's Java programming tutorial.

  Step 2. Use the algorithm you developed in Homework #1 and which we discussed in class, to find the maximum of the sequence of integers input in Step 1. Code the algorithm as a method maximum within the class P1Sequence.

  Step 3. Modify the maximum method to compute the minimum of the input sequence, and call this method minimum. Include this method in the class P1Sequence.

  Note: This method should return an int value.

  Step 4. Modify the minimum method to compute the mean of the input sequence, and call this method mean. Include this method in the class P1Sequence.

  Note: This method should return a float value, since the mean of the sequence will likely be a decimal number. This also implies that you should keep count of the number of input values, in order to compute the mean.

  Step 5. Modify the output statement in the classes HelloWorld and ForLoop in Dr. Crummer's Java programming tutorial to output your name, SSN, class code, as well as the number of integers read in, minimum, maximum, and mean of the input sequence, as shown in the example listed after Step 7, below. Include this as a method called writereport in the class P1Sequence.

  Step 6. Use different sequences of positive and negative integers (with different numbers of integers per sequence) to test your program. Your program should work on a sequence of any finite length (i.e., one or more integers).

  Step 7. After you have tested and completed your program, use the submission procedure outlined below to submit your project. You must pipe your input into the program from a file, not use command-line parameters for the data!!! The piping command is shown below under Example Test Procedure. The following relevant Java code fragment is taken from Dr. Crummer's tutorial, with the statement that reads stdin shown in green typeface:

  public class Count2 {
        public static void main(String[] args)
                        throws java.io.IOException              
        {
          System.out.println("Enter some chars,Ill count them (on UNIX, End with ^D):");
  
          int count = 0;
  
          System.out.println("Ill echo chars back to the screen (counting chars):");
          System.out.println("and Ill show you what the chars unicode values are.");
          System.out.println("Type, ending with  (on UNIX, End with ^D):");
  
          count = 0;
  
          int valueTyped = 0;
          while (valueTyped != -1) 
                 
               { valueTyped = System.in.read()  ;
                 count++;     
                 System.out.println(": you entered:" + valueTyped + " = " 
                                    + (char)valueTyped ) ;
               }
          System.out.println("Input has " + count + " chars.");
        }
  

  Instead of the variable valueTyped, you need to put the data into an array location (say, arrayInt[i], just to pick an array name).

  ---------
  TA Lloyd Noronha writes the following example:

   int v;
   int nextInt=0;
  
    //read the input until eof
    while ( (v=System.in.read()) != -1) {
      if ((v>'9') || v<'0') {
        if (nextInt != 0)
        //return the integer value when you hit the first
        // non-digit
          return nextInt;
        else
        //ignore multiple whitespaces
          continue;
      }
    //build the integer from the digit
    nextInt=nextInt*10+(v-'0');
    }
    return v;
  }
  

  This method returns the next integer from the input. If there are no more integers, it returns -1. Please put this method into class P1Sequence. Works only with positive numbers. The test will be performed only on positive numbers. Make sure that the method that uses this also throws IOException.

  ---------
  On Wed 26 May 1999, Sean Denney contributed the following code, which demonstrates reading of integers, and handles exceptions:

  
  import java.io.*;
  
  class Example throws IOException
  {
     int[] elements = new int[100];
  
     public Example(/**/)
     {/*constructor*/}
  
     public void readElem()
     {
        int i = System.in.read();
        element[0] = i;
        int j = 1;
        while(i != -1)
        {
           i = System.in.read();
           element[j] = i;
           j++;
        }
     }
  }
  

  Note that this code handles only one-digit integers, but the test would be made with two and 3 digit numbers also. Thus, it is better to use Lloyd's code, shown above, and we provide Sean's code as an illustration of exceptions only. Here follow a few comments from Sean:

  1. At the top of the class that uses the System.in.read method, import java.io.* .
  2. At the line of code where the class is defined, use the code fragment throws IOException .
  3. Using a while loop, use System.in.read to read in data from stdin. The loop should be exited when a -1 is encountered (indicates end of file).
  4. In this particular case, no try or catch command is needed.

  Thank you, Sean, for contributing this code.

  Example Output. Given the following input sequence, where brackets enclose comments not included in the sequence:

           23       [first number  in sequence]
           41
           16
           05       [4th  number  in sequence]
  

  your program output should look like this:

  
           John Smith     SSN: 123-345-6789
           28 May 1999    COP3530-C99-Proj1
  
           Numbers read in: 4
  
           Minimum = 5
  	 Maximum = 41
  	 Mean = 21.25
  
           - End -
  

  Example Test Procedure. Type up a text file "inFile" in either Dos or Unix with values like this: (As-of 5-26-99: use one integer per line of the file, to avoid I/O problems.)

  25
  35
  57
  92
  38
  56
  44
  101
  38
  

  Now run your program this way:

  java Proj1 < inFile

  Your sample output should look like this:

  
           John Smith     SSN: 123-345-6789
           28 May 1999    COP3530-C99-Proj1
  
           Numbers read in: 9
  
           Minimum =  25
           Maximum = 101
           Mean = 54.0
  

  Required Programming Procedure. Define each class in a separate .java file, with your master file as Proj1.java, where Proj1, which has a main method, is the class name that the TAs will use to run your program. (It is o.k. to have a main method in each class - the TAs are primarily interested in the main method in the Proj1 class.)

  Other Hints on Programming Procedure. Use the following steps to guide your implementation of the Java version of the preceding program.

  Hint 1. Get started early!!! Don't wait until the last two or three days, especially if you are new to Java programming.

  Hint 2. Decide what classes you will use (Hint: An Array or Vector object might be useful, with Reader class or objects, System class, etc.) After you have figured out what classes and objects to use, design your Java class specification(s) on paper. Then (and only then) should you start coding.

  Hint 3. Code your class(es) and methods, testing them incrementally (i.e., one at a time). Get each one working before you go on to the next one. If you write your program all in one blob of code, you will assuredly have difficulty debugging it.

  Hint 4. Try your program on different kinds of output (e.g., large and small inputs, with both negative and positive integers. If your code breaks, fix it until it works on all inputs. Use the pipe construct on the command line to get the input into your application.

  Hint 5. The TAs are here to help you with your problems. We have scheduled office hours throughout the week, with the exception of Friday, when the instructor and TAs will be working on grading homework assignments. Please feel free to ask the TAs any questions you may have about your Java program.

  Documentation. Illustrate your program with in-line comments, so the TAs know what you are doing. Consult your textbook and other Java programming references provided on the course Web page and elsewhere (e.g., Java books in library) for style guides.

• Evaluation. Maximum score = 50 points, as follows (modified 5-19-99 to allow for partial completion):

    Code Present & Clear               10 points max.
    In-line Comments & Documentation    5 points max.
    Code compiles correctly            10 points max.
    Data read in correctly              5 points max.
    Correct input count displayed       5 points max.
    Maximum computed correctly          5 points max.
    Minimum computed correctly          5 points max.
    Mean computed correctly             5 points max.
    -------------------------------------------------
    TOTAL POINTS                       50 points max.
  

  For example, if you have only half the code needed, and it doesn't compile and isn't documented, you would get half of the 10 points allocated for the code being present. If the code is present, well documented, compiles, reads in data, and displays the input count correctly (but doesn't do anything else), then you could get as many as 35 points.

• Submission Procedure. (Inserted Wed 5-19-99) Please submit only your *.java files. You must be logged in to your CISE account to perform the submission procedure. This procedure is described in detail in this link and is summarized below.

  Important Note: In case you have developed your programs on any environment other than the CISE Unix system, please test your program on a CISE Unix machine before submission. We will only be testing programs for grading purposes on the CISE Unix machines.

  Type in the following commands within your directory to submit all the java files for Project-1:

  turnin -c cop3530 -p proj1 *.java {Return}

  where {Return} denotes the carriage return key.

  Note: The turnin command has been activated, as-of late Friday 5-21-99.

• Due Date. Submit the completed project by Revised Due Date of 11:00am on Wed 2 June 1999. Projects submitted a day late will be penalized -10%; two days late: -20%, three days late: -30%, and four days late: -40% . Projects turned in more than four days late will not be accepted unless accompanied by a documented excuse (e.g., note from your physician or advisor).

This concludes the description of Project #1. Use the E-mail link at the top of this Web page to ask the TAs, if you have any questions about programming or grading.