CS 209 Sec. 52 Spring, 2006 Lab 4-A: Arrays Instructor: J.G. Neal Objectives: Lab Instructions: Obtain file ArrayDemoConsole.java

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1 CS 209 Sec. 52 Spring, 2006 Lab 4-A: Arrays Instructor: J.G. Neal Objectives: To gain experience with: 1. The declaration, creation, and use of arrays. 2. Inserting/removing items into/from an array. 3. Passing an array as a parameter to a method. 4. Performing operations on arrays. Lab Instructions: 1. Obtain file ArrayDemoConsole.java from instructor's webpage: 2. Create a new project for this assignment. The project and folder should be named Lab Compile and run the ArrayDemoConsole.java program. The input/output generated by the existing program consists of windows such as the following: 4. Extend the program. Now you will modify and extend the program as described in the following numbered steps. 5. Mod 1. Write the method arraytostring. Write a method named arraytostring. a. The method must take two parameters: (1) an array of elements of type int and (2) a number of type int representing the number of elements actually inserted into the array. b. The method must return a string that lists the elements of the array as one line of text, with a blank space separating each pair of successive elements in the array. This string must be comprised of just the elements actually inserted into the array. c. The returned string is intended for display purposes, to be printed by the calling method Page 1 of 6

2 to a Command Prompt window or a JOptionPane dialog or the NetBeans Output pane. d. NOTE: The instructor-provided program ArrayDemoConsole.java already contains an example method that is somewhat similar to the arraytostring method that you need to write. The existing arraysum method provides an example of passing an array as parameter. 6. Mod 2. Modify existing code within main for-loop. a. Change the display string Array elements: to Array A elements:. b. Modify the existing program code so that the new arraytostring method is called within the main for-loop to display the list of elements in each popup dialog after the text which you modified above. c. In other words, there is existing code at the bottom of the for-loop that creates a string of text to list the array elements entered thus far (in the previous passes through the loop body). The existing code consists of: arrayastr = ""; for (int j = 0; j < counta; j++) { arrayastr += A[j] + " "; } d. You are to replace this existing code with a call to the new method instead. When calling the new method, pass the array and element count into the method as parameters. e. As a result of your modification, the four lines of code shown above will be replaced by one line of code. The new one line will call the arraytostring method (with the parameters mentioned above) and assign the return value to variable arrayastr. 7. Mod 3. Modify the code that follows immediately after the for-loop. a. Modify the existing program code that follows after the main for-loop. This code creates three lines of text for output display. i. On the first line, the text should continue to show the total number of elements in the array. ii. On the second line, the text should continue to show the phrase The elements of array A:, followed by the list of the actual elements, all on one line. That is, the display of the final list of array elements in the Output pane of NetBeans should still look the same as in the window capture above, with the same explanatory label. However, the code must call the method arraytostring instead of using the variable arrayastr. iii. On the third line, the text should continue to display the sum of the array elements. 8. Mod 4. Add code to display a JOptionPane dialog after the for-loop. a. The dialog should display all of the output listed above as part of Mod 3. b. This same output string should be displayed to both the NetBeans Output pane and the newly added JOptionPane dialog. 9. Mod 5. Create and populate array B. a. In the main method of the program, declare and create a second array named B. When declaring the new array B, the size of the array should be specified using the same symbolic constant as used for the existing array A. Do not declare another constant. That is, use the same unmodifiable (final) variable as is currently used to declare the size of array A. Page 2 of 6

3 b. Add another for-loop to populate the new array B. The new for-loop should get each array element for array B from the user using a JOptionPane popup dialog, just as for array A. c. Each popup dialog must list the elements entered thus far for array B, just as for array A, and the name of the array must be displayed as B (not A). The arraytostring method must be called, just as for array A. d. Add the new for-loop for array B below the code that deals with array A. 10. Mod 6. Display the number of elements, contents, and sum for array B. a. After the for-loop that populates array B (described above), add code to display the following (just like for array A): o The number of elements in array B. o The list of the elements in array B. Be sure to invoke the method arraytostring. o The sum of the elements in array B. Be sure to invoke the method arraysum. b. Make sure that the array name B is displayed wherever the array name A was previously displayed. c. Add code to display the results in the JOptionPane dialog as well as in the Output pane of NetBeans, just like for array A. Make sure that the data for each array is displayed with the correct array name (A or B). Show the information on both arrays A and B in the JOptionPane dialog. 11. Mod 7. Present a final display of all the program output in a JOptionPane dialog in addition to the Output pane of NetBeans. In this JOptionPane dialog, display all the information that was previously presented on both arrays including the number of elements, list of elements, and sum of elements for each of arrays A and B. Be sure to invoke methods arraytostring and arraysum for each array. Be sure that the information on each array is presented with the correct name of the array (A or B). 12. Format the source code properly: a. Reformat the Java code so that it has proper indentation and vertical and horizontal alignment. b. Be sure to have a blank line right above and below each method definition. 13. Compile and debug your modified program. Test your program using a sufficient variety of data to make sure that it works on all cases. Test using a mix of positive, negative, and zero integers. 14. Run the program and make the following window captures. Paste the window captures into your ReadMe document as described in the next numbered step below. Be sure to include a window capture of each of the different windows used in your program, including: o One of the JOptionPane dialogs that prompt for entry of an element for array A, after at least three elements have been entered. o One of the JOptionPane dialogs that prompt for entry of an element for array B, after at least four elements have been entered. o Each of the JOptionPane dialogs that present output information on the arrays, including the final dialog that shows the data on both arrays A and B in one dialog. o The Output pane of NetBeans showing the complete final output of the program. Page 3 of 6

4 Examples of these windows are shown below. 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 number (e.g., Exercise #4-A ). Then enter any comments regarding the assignment. Your comments might include any difficulties encountered, suggestions for improvement of the assignment, etc. Then insert window captures mentioned in the numbered step above. Be sure the ReadMe document file is in your top level 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 must 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-04A.zip. Do not use spaces in the name of the file, use hyphens instead. TO RECEIVE CREDIT FOR YOUR PROGRAMMING EXERCISE: Submit the following for credit to Angel Drop Box for Exercise 04A: a. The zip file containing your entire NetBeans project folder with all its subfolders and files. b. You must have a batch file to run your program without using NetBeans, and the batch file must be within your top level NetBeans project folder. c. You must have a ReadMe file that contains your name at the top, the lab exercise number, any comments regarding the assignment, and window captures to show the entire program execution. The ReadMe file should show examples of all the different input and output windows. The ReadMe file must be in the top level NetBeans project folder. d. Your zip file must have a name consisting of your name along with the assignment number, as follows: JohnJones-04A.zip. e. You must submit your zip file to the Lab04A Drop Box for this CS 209 course in Angel ( DUE DATE: Tuesday, February 14. Sample window captures for the completed program are shown below: Page 4 of 6

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