CS 209 Spring, 2006 Lab 11: Files & Streams Instructor: J.G. Neal

Transcription

1 CS 209 Spring, 2006 Lab 11: Files & Streams Instructor: J.G. Neal Objectives: To gain experience with basic file input/output programming. Note: 1. This lab exercise corresponds to Chapter 16 of the textbook. 2. First, in this lab exercise, you will run and test an instructor-provided program. 3. Then you will extend your program from Lab Exercise 8 to include the saving and retrieving of employee data to/from file. Lab Instructions: 1. Obtain program files from instructor s webpage. EmployeeMultiTypeSeqFileExer.java: main class/file and driver for the demo program. EmployeeMultiTypeOpenListener.java: listener class containing event handler method for opening and reading a sequential file comprised of multiple data types. EmployeeMultiTypeSaveListener.java: listener class containing event handler method for writing a sequential file comprised of multiple data types. Employee.java: file to be used only to run the instructor-provided program; contains only a rudimentary tostring() method. 2. Create a project in NetBeans for this assignment. Add the four (4) instructor-provided classes (files) to the project. Run and test the program as indicated below. 3. Run the program comprised of the instructor-provided files mentioned above. To run the program, run the file EmployeeMultiTypeSeqFileEx.java. Note: This program only writes and reads part of the Employee data to/from file. As explained below, your job is to extend your Lab Exercise 8 program to include capabilities for writing the list of employees (including all their attributes) to file and reading a list of employees (including all their attributes) from a file. 4. Test the functionality of the instructor-provided program. If you enter an integer in the first field and hit the Enter key, the data on the employee in that position in the list (array) is displayed in the JTextFields. If no employee has been inserted into the selected list position, a message to that effect is displayed. If you enter data in all the fields and hit the Enter key in any field other than the first Employee Position field, then: i. if the array cell at the indicated position is empty, the employee is added to the array; ii. otherwise, if there is an object in the array cell at the indicated position, then the employee object is replaced with an employee created using the new updated data. After having entered several person objects into the array, click on the Save File button. This will write the array of Employee objects to a file, whose name and location is specified by the user. Important note: The saved file is not a text file, and therefore cannot be read or viewed in a tool such as Microsoft Word, NotePad, or WordPad. The data items are saved in binary form. After having saved the list of Employees to file by clicking the Save File button, exit the program. To do this, click the X button in the upper-right corner of the window. Re-start the program. Do not enter data on any Employees. Instead, click the Open File Page 1 of 8

2 button, and specify the name and location of the file to which you saved the list of employees in the previous step. The program should read the file and display the list of employees in the JTextArea. You should then be able to continue to add and change employees in the array list. You should be able to save the Employee list to file whenever desired, or open (read) an employee list from file into the program, as desired. 5. Instructions for file writing and reading. In this program and in the program that you will write as part of this exercise, file writing and reading is performed using the methods of the DataInputStream and DataOutputStream classes. These classes are used because they provide methods to read/write the different Java data types. The class MultiTypeSaveListener contains code that writes a list of employees to a file. This class illustrates how to write each item to file in its binary form using the methods of the DataOutputStream class. As part of this exercise and as illustrated in the class MultiTypeSaveListener, your code must write each data item to file in its binary form: i. Text string data items are written to the file as Strings of variable length. Since the strings are of variable length, a semi-colon is used as the special character to mark the end of a string in the file. Use the method writechars from the DataOutputStream class. o Employee member variables of type String: name, employee type, job title. ii. Integers are written as binary ints. Therefore, each has the same fixed length, namely 32 bits (4 bytes). Since all ints have the same fixed length, no special character is needed to mark the end of an int. Use method writeint from the DataOutputStream class. Do not insert a special character to mark the end of an int. o Employee member variables of type int: idnumber. iii. Decimal numbers are written as binary doubles. Therefore, each has the same fixed length, namely 64 bits (8 bytes). Since all doubles have the same fixed length, no special character is needed to mark the end of a double. Use method writedouble from the DataOutputStream class. Do not insert a special character to mark the end of a double. o Employee member variables of type double: payrate, hoursworked, The class MultiTypeOpenListener contains code that reads a list of employees from a file that has been written by the program. This class illustrates how to read each item from a file containing the data in binary form, using the methods of the DataInputStream class. As part of this exercise and as illustrated in the class MultiTypeOpenListener, your code must read each data item from a file containing the data in binary form. 6. In the next steps, you will modify and extend your Lab Exercise 8 program so that all the data on all the employees is written to a file and read from a file. 7. Mod 1. Add panel of buttons for file operations to your Lab Exercise 8 program. Copy the code from the file EmployeeMultiTypeSeqFileExer.java that creates and adds the button panel for file operations to the GUI (the panel containing the buttons Open File and Save File). The primary code should consist of lines Paste this code into your Lab 8 program. Copy and paste any other necessary related code also (e.g., declaration of the file-related Page 2 of 8

3 variables in lines Make any other necessary modifications to the code. This would include making it consistent with your Lab 8 program. 8. Mod 2. In class EmployeeMultiTypeSaveListener, add code to write all the rest of the data on every employee to file. In the actionperformed method, modify and extend the code so that it writes the rest of the data on each employee to file. The only employee attributes that are currently written to file are the name and idnumber. You must add code to write the following member variables or attributes to the file in addition to the name and idnumber: i. employeetype as a String (of any arbitrary length) ii. job title as a String (of any arbitrary length) iii. hoursworked as a double. iv. payrate as a double. 9. Mod 3. In class MultiTypeOpenListener, add code to read all the rest of the data on every employee from file. In the actionperformed method, modify and extend the code so that it reads the rest of the data on each employee from file. The only employee attributes that are currently read from file are the name and idnumber. You must add code to read the following member variables or attributes from the file in addition to the name and idnumber: i. employeetype as a String (of arbitrary length). ii. job title as a String (of arbitrary length) iii. hoursworked as a double. iv. payrate as a double. 10. Mod 4. Make any other necessary additions and changes to your program. 11. Run, test, and debug your program. Make sure that all the member variables are written to file by the Save File handler. Make sure that all the member variables are read from file by the Open File handler. Perform the following test when running your program: Create an employee list, write the list to a file, and exit the program. Then re-start the program and read the employee list from the saved file. Make sure that the employee list displayed in the program s JTextArea is the same as it was just before the list was written to file. 12. After getting the modified program to work correctly, make window captures for submission for credit. 13. See the figures below for window captures of the finished working program. 14. Create batch file. Create a batch file as you did for previous assignments so that your program can be executed without the use of NetBeans. Be sure that the batch file is within your top level NetBeans project folder 15. Create ReadMe file. Using Microsoft Word, create a file named ReadMe. In this document, insert your name at the top, and on the next line insert the assignment Page 3 of 8

4 number. Then enter any comments regarding the assignment and your program. Indicate whether you did the extra credit part of the assignment. Then insert your window captures that demonstrate that the program works correctly. If you did the extra credit part of the assignment, be sure to state this in your ReadMe file. Also, include window captures that demonstrate the extra credit capabilities. Be sure the ReadMe document file is in your top level NetBeans project folder. 16. Zip the project folder and all its contents. Create a zip file that contains the entire contents of your NetBeans project folder, including all sub-folders and files. Your project folder should contain your ReadMe file and batch file, as for previous project assignments. Change the name the zip file so that its name consists of your name along with the assignment number, as follows: JohnJones-11.zip. Do not use spaces in the name of the file, use hyphens instead. 17. Extra Credit: Do A or B: A. Add code to store the user-selected file name in the GUI class and report file operations to the user. Add a private member variable, named filename, to the JFrame subclass of your program. The variable must be used to hold the name of the file selected by the user. Add a public method, named setfilename, that sets the value of the filename variable. This method should be added to the same JFrame subclass of your program. Add a public method, named getfilename, that gets the value of the filename variable. This method should be added to the same JFrame subclass of your program Add code that invokes the above-mentioned methods to set or get the filename value, as appropriate. This code should be added to the two handler methods that read and write files so that the name of the user-selected file is held within the main class as the value of the filename variable. The filename must be changed (set) when the user selects a different file to write/read. Add code that reports when a file operation is performed along with the file name on the GUI at the top of the JTextArea. The code must display (1) whether the file operation was a read or write, along with (2) the name of the file. A message should be displayed each time a file is written or read. A message should only be displayed if a file read/write has just been performed. B. Add code to your newly enhanced and modified program that enables the user to insert and retrieve employee objects into/from user-specified positions in the employee array, as in the instructor-provided demo program. Use the instructor-provided EmployeeMultiTypeSeqFileExer.java file as an example of how to implement the desired functionality. TO RECEIVE CREDIT FOR YOUR ASSIGNMENT: Submit the following for credit to Angel Drop Box for Exercise 11: a. The zip file containing your entire NetBeans project folder with all its subfolders and files. Page 4 of 8

5 b. You must have a batch file to run your program without using NetBeans, and the batch file must be in your top level project folder. c. You must have a ReadMe file that contains your name at the top, the lab number, any comments regarding the assignment, and window captures to show the program execution. The ReadMe file must be in the top level project folder. d. You must submit your zip file to the Lab11 Drop Box for this CS 209 course in Angel ( DUE DATE: Tuesday, April 25. EXAMPLES OF PROGRAM EXECUTION: Page 5 of 8

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