Program 12 - Spring 2018

Transcription

1 CIST 1400, Introduction to Computer Programming Programming Assignment Program 12 - Spring 2018 Overview of Program Earlier this semester, you have written programs that read and processed dates in various ways. You will read dates from an external text file and identify which two dates in the file have the fewest number of days between them and which two dates have the largest number of days between them and output those pairs of dates and the number of days between each pair. For this program, you will be provided with a Date class that you will use to store and process dates with so that you don't have to manage that information manually. This should enable you to focus on the logic of the program itself rather than adding in details of storing and processing the dates. NOTE: See later in the assignment for details on how the output should be formatted. Writing two methods on your own For this program, you will also need to implement at least two additional methods other than main(). These methods can accomplish whatever task you want them to, such as: read the file of dates, sort an array of dates, display the list of dates, find the smallest range between two dates, find the largest range of dates between two dates, etc. The methods you write will need to have complete Javadoc documentation and be used (called) at least once each during your program's execution. It is acceptable to write more than two additional methods if you would like in order to practice breaking programs into smaller, more manageable units of code.

2 Format of the file The file that you will read dates from will look like this: 5 1/1/1900 1/2/ /5/1798 7/4/3001 8/1/2028 The first value of the file will be an int value indicating how many dates will be present in the file. The value could be any value from 2 and up. Each file will be guaranteed to have at least two dates in it. Each date in the file will be on a line by itself and will be in the format of MM/DD/YYYY, where MM is the month, DD is the day, and YYYY is the year. Information about easily processing dates in this format is discussed later in this document. For this program, all dates in a file will be valid dates, but functionality is provided within the Date class to identify invalid dates and handle them appropriately. There may be duplicate entries for the same date in the file. Dates can be in the range 1/1/1753 to 12/31/3000. Reading input from a file instead of the keyboard In order to process a file for input instead of keyboard input, you'll need to be able to open and read from a separate text file in Java. There are a number of different ways to do this, and you'll explore more involved ways to process files if you take more programming courses, but for what we need this semester we'll create a Scanner that is attached to a file so that input will basically behave the same way that you've been processing things all semester, just from a file instead of the keyboard. To practice with this idea, first create a file named test.txt in the same directory that your program file will reside in that looks like this:

3 Now edit a file called TestingFileInput.java in jgrasp and place the following code into it. Compile and run the code to see what it does. Pay close attention to the throws FileNotFoundException code added to the header of the main() method, which is new and only necessary right now when processing external files: import java.util.scanner; import java.io.file; Import java.io.filenotfoundexception; Java public class TestingFileInput { public static void main (String args[]) throws FileNotFoundException { // Create a regular Scanner for keyboard input Scanner keyboard = new Scanner(System.in); // Now create a String variable and read the filename System.out.println("Enter input filename: "); String infile; // Notice the use of the System.in Scanner for this input infile = keyboard.next(); // Need to create a File variable based on the infile file name File file = new File(inFile); // Now create a Scanner attached to the file instead of System.in // This Scanner will be used for file input!!! Scanner fileinput = new Scanner(file); // Read something out of the file, which is an integer int v1 = fileinput.nextint(); System.out.println("First int of the file is : " + v1); // Set up a loop that reads the rest of the int data from the file System.out.println ( "Now reading the rest of the data!" ); for (int which = 0; which < v1; which++) { int v = fileinput.nextint(); System.out.printf("A value from the file: %d\n", v); } } }

4 The code doesn't compile with a really weird error! Your program may not compile with an error that looks like this: FileInput.java:18: error: unreported exception FileNotFoundException; must be caught or declared to be thrown Scanner fileinput = new Scanner(file); If this happens, make sure you go back and add in the throws FileNotFoundException code on the main() method header line. This should take care of that situation. The program uses multiple Scanner variables! What? You should notice that the example program creates two different Scanner variables. Variable keyboard is used to read the filename from the keyboard, as we've been doing all semester so far. Variable fileinput is connected to an external file to pull data from. Okay, it compiles and runs... what now? When you run the code and are prompted for a file name, enter test.txt or whatever you called the file you created. If the file exists, the program should read the data from that file and output it to the screen. Notice what happens when you enter a filename that doesn't exist; the program should exit with some sort of error like this: Exception in thread "main" java.io.filenotfoundexception: test.data (No such file or directory) at java.base/java.io.fileinputstream.open0(native Method) at java.base/java.io.fileinputstream.open(fileinputstream.java:196) at java.base/java.io.fileinputstream.<init>(fileinputstream.java:139) at java.base/java.util.scanner.<init>(scanner.java:611) at FileInput.main(FileInput.java:18) It is important and imperative that you work with this code until you are certain you have a good handle on how it's setting up an external file for reading before moving on to the next part of the assignment.

5 What can objects of the Date class do? A Date object can store a date between 1/1/1753 and 12/31/3000. Objects of Date class have the following public methods available for you to use. Please note that you do not need to write these methods; they are available for you to use in the Date class that is provided in the Date.class file you will download. You don't need to use any import statements or anything fancy to use the Date class. Just create a new Date object in your program using the constructor as described below and you can move forward from there. Method Date() Description and Example Default constructor, used to create a new Date object. The date is set to 1/1/1753. Date d1 = new Date(); Date(int m, int d, int y) Specific constructor, used to create a new Date object with a given date. Date d2 = new Date(11,27,2017); setdate(int m, int d, int y) Attempts to set the date to the given month m, day d, and year y. Returns true if the date was valid. Returns false and sets the date to 1/1/1753 if the attempted date was invalid. d1.setdate(4,1,2018); dayssince1753() Returns an int value denoting how many days since 1/1/1753 the object's date is. int w = d2.dayssince1753(); tostring() Allows printing of the object's date. System.out.print(d2);

6 Determining Closest and Furthest Dates Closest Dates The closest dates will be determined by comparing each date to all of the dates in the file except for itself. The result may be 0, but only if there are duplicate dates in the file. Furthest Dates The furthest dates will also be determined by comparing each date to all of the dates in the file except itself. Given the storage range of dates possible in a Date object, the maximum number of days between dates could be Examples See the sample runs at the end of the file for examples of different results. Considerations for Entering and Validating Dates Entering Dates For previous assignments when entering dates, the month, day, and year needed to be entered separately. For this assignment, you'll change a property of the Scanner attached to the file that you create so that you can read dates in MM/DD/YYYY format. By default, a Scanner uses whitespace like spaces and newlines (enter/return) to identify different pieces of input, like this: Scanner get = new Scanner( System.in ); Java System.out.print("Enter your date: "); int m = get.nextint(); int d = get.nextint(); int y = get.nextint();

7 Input to this code could be entered like this: Enter your date: or like this: Enter your date: Either way, variable m would get a value of 4, variable d would get a value of 16 and variable y would get a value of Changing Scanner behavior In order to enter dates in MM/DD/YYYY format, using slashes, the Scanner attached to your file needs to behave differently. The easiest way to do this is to change the way the Scanner reads values from the keyboard. As mentioned in the last section, a Scanner uses whitespace as a delimiter between input by default. To change this behavior, you can use the usedelimiter() method from the Scanner class. More information about the usedelimiter() method can be found at To enable a Scanner to use, for instance, slashes / as delimiters in addition to spaces, you can use the following code in your program: Scanner get = new Scanner( System.in ); get.usedelimiter("[/\\s+]+"); // notice two backslashes here! Java System.out.print("Enter your date: "); int m = get.nextint(); int d = get.nextint(); int y = get.nextint(); Now, dates can be entered in any of the following four ways: Enter your date:

8 or Enter your date: or Enter your date: 4/16/2018 or Enter your date: 4 / 16 / 2018 The usedelimiter() method changes the behavior of the Scanner by providing a list of items that can be seen as delimiters between pieces of information. [/\\s+]+ tells Java that it can use either a forward slash / or a whitespace character \s (such as space, return, etc) to identify different inputs. The key to having this work with input from a text file is to apply the.usedelimiter() method to the Scanner you would like to change the behavior of. So, if you have a Scanner attached to a file, then you want to use the.usedelimiter() method on that Scanner.

9 Output The output of your program should look like the following sample: Enter filename to process: d1.txt The sorted dates from the file are: 1: 11/30/1955 2: 11/23/2015 3: 11/24/2015 4: 11/25/2015 5: 11/26/2015 6: 11/28/2015 7: 11/29/2015 8: 11/30/2015 9: 12/02/ : 02/23/2016 Closest (1): 11/23/2015 and 11/24/2015 Furthest (22000): 11/30/1955 and 02/23/2016 Make sure to include the following items in the format seen above: The program should output a list of the dates themselves, one per line, sorted from earliest date to latest date. Then output the dates that are "closest" to each other, including the number of days between the two dates, in "sorted" order with the earlier date listed first. Finally, output the dates that are the "furthest" from each other, including the number of days between the two dates, in sorted order with the earlier date listed first. Get a copy of the files to work with, including the Date class You can download a ZIP file containing 8 sample data files, the Date.class file containing the Date class to work with, and starter code that sets up the code to read from a file for you to work with from Canvas.

10 Download and unzip the compressed file and you should have the following files: File Date.class FileOfDates.java d1.txt - d8.txt Description The compiled class file that you can use for the Date class The starter code you can use to begin your program The files of dates to process Goals Use a non-standard, predefined class to implement a solution to a program. Read data from a text file Perform sorting on an array of objects Class and File Naming Name your class FileOfDates and source file FileOfDates.java. Testing Your Program Check out the sample run at the end of the assignment as well as some other example data values to test. Working With New Concepts / Developing This Program Before diving into working with the Date class for this program, it would be useful to write a small program that uses the Date class in a number of different ways so that you practice with the methods of this class and are familiar with the way they work. You will need to store the dates you read from the file into an array. Working with an array of Date objects behaves the same way that working with an array of String objects does. Grading Notes For the output, follow the format of the sample runs as closely as possible. The order of the dates for the closest and furthest dates can be in either order. Additionally, you must have a completed Collaboration document on file in order for the program to be graded.

11 Grading Rubric NOTE: If your submitted assignment does not compile, you will receive 0 points. We are unable to test code that does not compile. Insuring that your code compiles is critical when developing programs. We would rather grade an incomplete yet operational program than a program that we can't test. Item Points Notes Style/Coding (WebCAT): Documentation/style of source code Design/Readability (GA): Useful variable names Write additional methods (GA) Have header documentation that includes your name and other relevant information and javadoc for all methods. Meets expectations in CIST1400-checkstyle_intermediate.xml. Consistently use descriptive variable names, and code is well thought out. Implement, use, and adequately document at least two additional methods in your program Correctness/Testing: TaskXX() testing 24 Follow expected output as shown in Sample runs.

12 Sample Run for file d2.txt Enter filename to process: d2.txt The dates from the file are: 1: 01/01/1753 2: 11/27/2017 Closest (96754): 01/01/1753 and 11/27/2017 Furthest (96754): 01/01/1753 and 11/27/2017 Some Other Test Data From Files Included in Copied Directory File Number of Dates Closest Days Closest Dates Furthest Days Furthest Dates d1.txt /23/2015 and 11/24/ /23/2016 and 11/30/1955 d2.txt /01/1753 and 11/27/ /27/2017 and 01/01/1753 d3.txt /27/2017 and 11/28/ /29/2019 and 11/27/2017 d4.txt /06/2679 and 01/22/ /04/1826 and 01/15/2969 d5.txt /17/1928 and 08/21/ /22/1763 and 09/05/2993 d6.txt /29/2100 and 05/29/ /23/2096 and 07/07/2972 d7.txt /22/2648 and 12/19/ /22/1774 and 02/18/2998 d8.txt /14/2577 and 07/15/ /19/1781 and 11/30/3000