10403 Lab and Eclipse Introduction (Last updated by asanchez, jcomer 1/18/18)

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1 10403 Lab and Eclipse Introduction (Last updated by asanchez, jcomer 1/18/18) 1 I. Access and check your student account. 1. Log into the TCU network with your TCU student account Username and Password. (If your password does not work, try your original password - DDMMMYY of your birthday. For example, 05MAR79.) Username: Password: Domain: TCU If at anytime during the semester you have problems with your account or password you should go to Information Commons Help Desk on the first floor of the TCU Library. The phone number to the Help Desk is X5855. If you have Internet access, you can reset the password on your account by accessing 2. Take a moment to familiarize yourself with the Windows XP desktop. Find each of the applications noted below. You should realize that the desktop might look a little different on different computers. Internet Explorer The web browser you should always use to check the execution of your Java applet on the web. ECLIPSE IDE - The integrated development environment (IDE) used to create your Java programs. This program is available from the Start menu and may also be available from a desktop shortcut labeled Computer Science Applications. TURNIN - A program used to submit your Java source code for grading. This program is available from the Start menu and may also be available from a desktop shortcut. 3. Double-click on My Computer to access the various resources of this machine. Besides the usual C: and D: drives you should see a shared W: //studentweb/ with your username. This is your TCU student drive space and the location you will store your work for grading. You will be able to access it from any computer connected to the TCU network or that can connect to the Internet. IF YOU CANNOT LOGIN OR DO NOT SEE YOUR W: DRIVE, STOP HERE AND GET ASSISTANCE IMMEDIATELY! (Your account may not be set up correctly yet.) 4. It is wise to occasionally check the available storage space of your student account on your W: drive. To check the space you can open the W: drive (by double-clicking), from the Edit menu select Select All, right-click on the highlighted icons and select Properties from the drop-down menu. You will be shown the amount of used space on your account. Make sure to always keep plenty of available space for saving lab projects and your . Most student accounts are given 50 Mbytes (approx. 50,000,000 bytes) of storage. If your space quota is exceeded you will not be able to run and save your labs correctly!

2 II. Prepare a wwwpub directory on your W: drive. (Done only ONCE.) 2 1. At this point you need to obtain some files to set up a WWWPUB directory on your W: drive. (Note: you must be in one of the labs on-campus in order to perform the following steps). For Windows 8: Right click the bottom left Windows icon and select the Run application and selected it should look as follows: Type in in the search \\tcu.edu\dfs1\lab_common\cosc_10403 and hit OK. The window shown below should appear. For Windows 7: Go to the MS bottom flag or start Button and Select Run. Type in \\labsrv1\lab_common\cosc_10403 or \\tcu.edu\dfs1\lab_common\cosc_10403 and hit OK. The window shown below should appear. 2. Open MyComputer by double-clicking on the icon.

3 3. Inside the window just opened for MyComputer, open your W: drive. If you already have a wwwpub directory on your w: drive delete the wwwpub file; otherwise, continue with Step 4 below. 4. Copy the entire WWWPUB (not the WWWPUB.zip) directory and its contents from COSC_10403 onto your W: drive. NOTE that if in your W: there is already a previous wwwpub folder you should delete this one and copy the new one 5. Close your W: drive. Skip to Step Do this step ONLY if you did not do Steps 4-5 above (because you already had a WWWPUB directory on your W: drive). Open WWWPUB in the COSC_10403 directory. Select all items inside the WWWPUB directory in COSC_10403 and drag them into the already existing WWWPUB folder on your W: drive. Close your W: drive. 7. Now let s verify that WWWPUB has been created correctly. Open your W: drive by double-clicking. Open WWWPUB directory on your W: drive. You should see Lab0-9 folders and a 10403labs.html icon as shown below. If you do not see a window with the Address and contents EXACTLY as shown below, ask for assistance. Currently the folders are all empty. As you finish each lab this semester, you will place specified files in the appropriate lab folder. These files can then be accessed from a web browser to demonstrate the execution of your Java applet for grading Close all windows except these instructions.

4 III. Use Eclipse (version NEON) to create and run a Java applet. Eclipse is an open source IDE (integrated development environment) available to programmers who want to develop Java projects. Since it is an IDE, the tools needed for editing, compiling, building, debugging, executing, and obtaining online help are all integrated in one graphical user interface. Using these tools effectively can greatly increase your productivity. However there are many options available and you may get easily confused; follow these instructions to gain an initial feel for the IDE, later you can spend time using the various options. The current version of Eclipse are using is OXYGEN. 1. Before beginning, you should create a COSC10403 folder to hold all of your work related to this class. Note: this folder should reside on your W: drive (but outside of your wwwpub folder)! 2. Start Eclipse by selecting Eclipse from the Start menu or by double-clicking the shortcut found inside the Computer Science Applications desktop folder on TTC lab computers. The first thing that you have to do is to select the workspace area where you will store your Eclipse Java Programs. This workspace will most commonly be the COSC10403 folder that you created in Step #1 above - so you may simply select OK after Browsing to get to that location If the Eclipse Welcome Window appears, close it by clicking on the X to the far right of its title bar. (Note that the welcome page in Eclipse Neon may be a bit different) Click Here!! yyyvvvdddyou You AND Click Here!! yyyvvvdddyou You

5 After this, you should now be observing only the File, Edit, Source bar and the various Package, Tasks and empty windows (as seen in the figure below) If this is your the first time to launch Eclipse, your Package Explorer window should be empty indicating that you have not yet created any projects; if you have used Eclipse before other Java projects may be listed (for example Lab0Project, Lab1Project, Lab2Project, and so on). To continue working on a project that was begun earlier, simply click on the desired project in the Projects window and continue with the development. Note: To switch between Projects, Files, or Services windows, simply click on the desired window s title bar. 5. To create and run a new Java program you must first create a project. Follow the steps below a. Choose New/Java Project from the File menu. The screen below should appear. Make this selection. The following window appears - to create a new project, let us name it as Lab0Project and select Next. (Note: you should always name your projects as: LabiProject, where i will correspond to the current lab number).

6 6 Name your project: Lab0Project and make sure that the Java 1.8 version is selected A new window appears, simply select Finish The Project Explorer window will show a new folder named Lab0Project Lab0Project

7 7 6. Create an initial class for Lab0Project Choose New Class from the File menu. The screen below should appear. Make this selection. Name your class as Lab0, as follows: Name your project: Lab0 (Note that it will be stored as Lab0.java) in the src folder of your Lab0Project. Press the Finish button.

8 8 After you select Finish the right window of the IDE will display the source code for this new class (as shown below): The source code of the selected java class is displayed in this window. Note that Eclipse provides some start up code to help you get started. The explorer highlights the selected Lab0.java as the current working file for editing. 7. Editing a java file. For this initial practice, replace (overwrite) the java source code in the right-side window with the following new java code EXACTLY as it is given here. (Otherwise you will have Java errors and the program will not run): import java.awt.*; import javax.swing.*; public class Lab0 extends JApplet { JLabel l1 = new JLabel("TCU is great - Hello World"); public void init() { setlayout(new FlowLayout() ); add(l1); } } System.out.println("This output will appear in the console window"); Your source code window should now look like the following:

9 9 Selected java reserved words will automatically be color-coded. We will be discussing the significance of each of these Java statements in class shortly but here is a brief explanation. The two import statements are needed to allow your program to access two predefined packages of Java code (useful for developing GUI s). The public class is your Lab0 program and it consists of the init method. Each method is a set of instructions separated by semicolon (;) and enclosed in braces { }. The complete class is also enclosed by a pair of { }. 8. Running the program To run your program you must insure that the class Lab0.java file is highlighted in the rightside Package Explorer window. From the top menu bar, choose the Run/Run As/Java Applet option as follows: Run As/Java Applet The Run command is part of the options in the main menu Before running the program, the IDE may need to first compile your program. If this is the case simply select OK.

10 10 This window displays the applet class named Lab0 your program When running your program, it should open a window in the upper left corner (as shown below): Note that you can also run your program using the green and black arrows in the tool bar (as shown below) 1. About source and binary Java Files After your program has successfully executed an inspection will reveal that you now have two folders stored in your original Lab0Project folder. An src folder (containing the java code that you entered earlier) and a bin folder (containing a Lab0.class which is the actual code that will ultimately be executed by the computer). To verify this, open the COSC10403 folder. Opening a window in XP (i.e. outside Eclipse) you should have two subfolders in the Lab0Project, a bin and a src. Opening the bin and src folders will show the screen shots below (note this is done outside of Eclipse, using the Windows explorer)

11 11 In your COSC10403 folder you will find a subfolder for Lab0Project that contains two subfolders: src and bin The bin folder contains the Lab0.class file, while the src folder contains the Lab0.java source In the bin folder you have the object code of your program Lab0.class (this is actually the code that the machine executes). In the src folder you will find the source code of your program Lab0.java (what you typed earlier). a. Saving and copying your files. Your files are automatically saved before any run command, but you can also select to save the file using the File Save option once you have selected the given file. As seen in the previous windows, if you are using computers located in one of the TCU labs (e.g., TTC 353/357, Library, etc), your files are most likely being saved on your W: drive in the COSC10403 folder that you created at the beginning of the IDE session. If you are using your own computer, at home on in your dorm room, your files most likely reside on your local C: drive. You will have to take steps to transfer both the.class and.java program files to your TCU W: drive in order for your work to be graded. (We cover this topic in section IV of this guide). 2. Creating a New Project Back again in the Eclipse IDE, you can now use this initial template (saved now as Lab0.java) to create other projects. Create the new project by selecting the File/New/Java Project option and name the project Lab1Project (as shown in the window below):

12 12 Lab1Project In order to create a new class, this time let us use, as a starting point, the code we created for Lab0.java. Select the Lab0.java code and using the Save As option from the File menu, save the class in the src folder of your new Lab1Project. Console window this is where error messages will be displayed. This output will appear in the Eclipse console window. See the following screen. Note: that Lab1.java has been entered into the File name field.

13 13 Use the Save As to make a copy in the new project Lab1Project. In this way you now have a template for future projects. In this case the new name is After selecting the OK, you now have a copy of your Lab1.java file in the src subfolder of your new Lab1Project. You can use Eclipse to open it to edit this new java (as shown in the window below): You have to correct the errors you have. The IDE marks them with red flags. For this case the new class should be named Lab1 rather than L Obviously the IDE expects you to correct the errors in the new program before it will run; for example: the class should be named Lab1 instead of Lab0 since it is located in the Lab1.java file. Make that correction and run the Applet again, as you did with Lab0. For the sake of practice, modify your Lab1 class by EXACTLY replacing its current source code with the following code:

14 14 import java.awt.*; import javax.swing.*; public class Lab1 extends JApplet { public JButton haltb = new JButton("HALT"); } public void init() { add(haltb); } Run this applet from Run Run As Java Applet option using Lab1.java this time and you should get the following results: Results attained after running the applet. The new code that displays a button in the window applet. 3. Testing your Programs When you work on a new programming assignment you will enter Java source code for the new project (such as the Lab0.java file as done above) and test and retest it until everything looks perfect. Each time that you Run the program Eclipse generates two files: an updated Lab1.java file and a new Lab1.class file containing the new executable code. A default internal browser (the Applet Viewer) is then used to display the applet. Once you are satisfied with your program s results, and it is perfect you must submit the assignment for grading. TWO things must be done. i. YOU MUST place the program on the web for viewing. This involves copying specified files into the appropriate lab folder of the WWWPUB directory on your W: drive. (See Section IV below) and ii. YOU MUST submit your source code with TURNIN. (See Section V) 4. Other options in Eclipse

15 15 a. Occasionally, in order for your applet to be properly displayed on the web, you will have to make changes to the width and height parameters of the program. You can change these values by selecting the Run Run Configurations option from the top menu. From there select the Parameters Tab to change the width and height of the applet to be displayed. The default dimension is 200 pixels x 200 pixels. Using the Run Run Configurations command, By selecting the parameters tab you can change the Width and Height of the applet window For example in this case we have changed the width of the window to width = 400, height = 200. Running the applet again yields the following results (notice the different size window): Observe the larger dimensions. Also, observe that files will be automatically compiled and saved as needed, i.e., you do not have to explicitly save, then compile, then execute. b. As you can see the options available in the Eclipse IDE are multiple and one can get lost rather easily. You will need to use Eclipse for a while in order to become comfortable with it. For example you can add different views in your left most window by selecting on the menu bar Window Show View option as follows:

16 16 The navigator option will show you both the src and bin contents of your projects By using the Navigator tab you can now see both the src and bin folders for both projects that we ve created (as shown below). c. Closing Eclipse To close Eclipse you only need to get out of the application by selecting the exit option (in the right most corner). However, before you do that you may want to close the Applet you have running, you can do that by selecting the red square in the bottom window (as shown below)

17 17 You can stop the execution of your applet by selecting the red box in the console tab Exit. You should now have a working applet that runs inside Eclipse. Close all windows in preparation for the 4-step submission process outlined below.

18 IV. Place your lab on the web (in wwwpub) and access it from a web browser. In order to complete an assignment, and to prepare your applet to run on the web, five steps must be taken. These are: 1. Copying the contents of the assignment s bin folder (i.e., the.class file(s)) into the corresponding folder in your WWWPUB folder, 2. Prepare an html file that can be used to execute the.class file. 3. Enable the URL to allow the browser to run your Applet. 4. Use Firefox to validate that you applet is running properly over the web. 5. Use Turnin to submit your assignment s.java file to your instructor for grading. Note: this step should be done last only after you have verified that your applet is executing properly over the web!! 1. Step 1 copying contents of the object code This step involves copying ONLY the Lab0.class from bin folder from your COSC10403/Lab0Project folder into the corresponding Lab0 folder in your WWWPUB directory on your W: drive. The procedure below should work on-campus anywhere you have access to your W: drive. It will also be possible to FTP from off-campus using a browser ( or an FTP program such as Core FTP Lite. Open My Computer (by double-clicking on the icon). Open your W: drive. Open your COSC10403 folder and, finally, open the Lab0Project folder to view its contents. (Seen in the window on the left below.) Open the WWWPUB directory on your W: drive. Open the Lab0 folder inside your WWWPUB. (Seen in the window on the right below.). It should be empty at this point. 18 Note: The icons might appear differently depending on the operating system and viewing options that are set. Copy (DO NOT Move or Drag & Drop) the Lab0.class found in the Lab0Project folder into your wwwpub\lab0 directory. Copy by right-clicking on the Lab0.class,

19 19 selecting Copy, and then right-clicking inside the Lab0 folder and selecting Paste Note that the extension may not show, but you have copied the Lab0.class file in your LAB0 folder 2. Step 2 prepare the html file Write a simple html file to run your applet. In this case you will have to write the following html file and save it in you wwwpub\lab0 folder. To do this you should use Eclipse with the option file new Untitled Textfile File and then save it with the name Lab0.html in your Lab0Project Folder <html> <title>lab0project</title> <hr> <applet code="lab0.class" width=200 height=200> </applet> <hr> </html> Using Eclipse this how you create an text file: You should use the eclipse text editor to write the Lab0.html file. Note that you may need to change the width=xxx and Copy/Save this file into your WWWPUB\Lab0 folder and you will be able to run your applet from the web by pointing a browser to the.html file.

20 20 The Lab0.html file that was created. Note: Firefox is the default browser. The applet can be tested by doubleclicking on this file or by pointing a browser to the file. Note that both files the Lab0.class and the Lab0.html are in the LAB0 folder 3. Step 3 Enable the URL to allow the browser to run your Applet In this part you will instruct java to allow applets to run in your browser. For security reasons you need to register the URL sites that contain secure Applets. To do this follow the instructions given below. For Windows 8: Right click the bottom left Windows icon and select Control Panel and search for the java panel

21 For Windows 7: Look for the Control Panel in Windows. Using the MS bottom flag or start and search for control panels as shown below: 21 Search for control panel. and type the word java : For Windows 7 or 8, click on the java icon and you will get the following control window,

22 22 select the Security tab and there you have to register the following URL, this you do by editing the site list with the following URL s exactly as written here: file:/// Edit the Site List Once this is done select Apply and OK and you are ready to test you applet 4. Step 3 test you applet to insure that it is running properly Start-up one of the Java-enabled web browsers. Graders will use Internet Explorer 6.0 (or later) to grade the execution of your applet on the web - so ALWAYS make sure you view your applets in Firefox, in Windows machines in the lab we are using the 32 bit version. On your laptop machine make sure that the Firefox is the 32 bit version rather than the 64 bit, this because the newer versions of Firefox do not allow for the java plugin. Do not use Google Chrome. You may also use Microsoft InternetExplorer as long as it runs the java plugin

23 If your account is set up correctly, you should be able to run your Lab0 applet by typing (where you have to replace comer1 with whatever your assigned username is) for the URL and then clicking on the lab number you want to view, Lab #0 in this case. When running the internet explorer browser you might need to allow for ActiveX control, allowing the block content as follows: 23 Your applet executing over the web. Note: If you did not have a WWWPUB on your W: drive and have just created it for the first time, you will probably get the error The page cannot be found (shown below) when you try to access your 10403labs.html. This may be because the system has not yet run the update program to register your WWWPUB. (At last check with Technology Resources this update operation was being performed every hour, on the hour.) Try to view it again in an hour or so! If you still cannot access your Lab0 see your instructor immediately! You should not have this problem in future labs because the WWWPUB will already be created and updated

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25 Once your WWWPUB directory is registered you should not ever see this problem again. If you do get The page cannot be found message, it will probably be because you did not correctly place a Labx.html file in the Labx folder (x is the lab number). 25 IF THAT HAPPENS, GET IT FIXED IMMEDIATELY OR THE GRADER WILL ASSIGN A GRADE OF 0!! (The grader has nothing to grade!!) Note: If you get a dialog box asking for username and password, simply enter it and view your web page. (This indicates that World read permissions have not been given to your files yet. That should happen when Technical Resources runs a program to update the file access privileges currently every hour on the hour.) However, if this continues to happen, tell your instructor AND go talk to the TCU Help Desk personnel immediately! Always make sure you view your applet on the Web using Internet Explorer! Viewing the applet on the web is a major part of your lab grade!!! *** When you finish this operation, your W:/wwwpub/Lab0 directory should have the contents shown above. If it does not, ask for assistance. ***

26 V. Submit your Java source code (.java file) for grading TURNIN Run the TURNIN program to submit the lab for grading. TURNIN is accessible from the Start menu or possibly from a desktop shortcut. a. Enter your address (e.g., j.doe@tcu.edu) in the box provided, select your course & section number, and select the assignment to be turned in (in this case, Lab0) as illustrated below. Click the Submit button. b. If the information you entered was correct, AND your instructor has set up your Turnin account, you should be presented with a window that will allow you to navigate and find your.java file. You will receive a caution that only your.java file is to be turned in. DO NOT SUBMIT YOUR.html FILE OR YOUR.class FILE. You will get a grade of 0 (zero) if you do!!! Note: For some future labs you will be submitting a.zip file that will encapsulate several.java files together as a single file we will discuss this later. b. Navigate to the.java file you created for Lab0 (Lab0.java in the project s src directory) and click Open (or simply double-click the.java file). Be sure you only turn in the.java file with Turnin.

27 27 c. If the submission went through correctly, you should be given a receipt number on the submission screen. Be sure to keep the receipt number as this is your proof that you did submit the lab, should any questions arise. ***************Important**************** You must run the TURNIN program to submit your lab for grading. Turnin only the.java file. Always keep your receipt as proof of submission. Also, always verify the execution of your lab from the web using Internet Explorer and make absolutely sure it is submitted as the correct lab number! (This means going to and viewing the lab.) Later in the semester, if you experience any difficulties with the submission process, or viewing on the Web notify your instructor immediately! *************************************** 1. Your Lab 1 assignment has been posted on the Assignments web page. Go to and get your Lab 1 assignment now. You may begin work on it today, while an instructor is available for assistance. 2. Be sure to ALWAYS logoff of your account on the PC by clicking the Start menu on the Task bar, selecting ShutDown and Log off. If you do not do this, your account (and your labs) will be open to the public!

28 VI. Running a JApplet as a Java Application (VERY IMPORTANT) 28 Once you have your Applet running it is also possible to run it as stand alone local Java application I your computer. With this you gain the versatility of the Applet in your own machine, so if for any reason you can not see the Applet running in the browser, ypou will be able to run it locally by a simple double click application. Using Eclipse and Java, you will be able to do so as it is described below. This is a very important part since Java Applets eventually will stop running over the web, so in order to show your work you will have to run your programs as Applications outside of Eclipse. 1. Add a main class: First you have to add a main method to your Applet class. Copy the following code and add to your Applet class: public static void main(string args[]) { JFrame appletframe = new JFrame("Applet as an application"); appletframe.setlayout(new GridLayout(1,0)); appletframe.setsize(200, 200); // after the new put the name of your Applet Class JApplet myapplet = new Lab1(); myapplet.init(); myapplet.start(); appletframe.add(myapplet); appletframe.setvisible(true); } 2. Run the applet as an application: If you read through the code of the main method you will see that a frame is created, this frame is a pop up window that will serve as the browser call, to run the applet now you will see in the Eclipse menu two options: to run as an Applet or as an Application: if you select Java Application a pop up window will appear (we call it a Frame) looking as follows for the case we have been working on

29 29 Notice it runs under the title Running as application, rather than as it did before under the browser as the host ( STOP button rather than HALT button shown). 3. Creating a clickable Jar file: Now we want to create this program as single clickable application, Eclipse will help doing so, by selecting the option export if you click on the directory where you have the applet class, as follows: when you select the export function you will get a window asking the type of java jar you want, here you select runnable jar as follows:

30 30 by selecting the next button a new will appear asking to select the launch configuration where you have to select the directory and the java class you are working on, for this example in this case Lab1. Also you will need to determine the export destination and the name of the jar file, for this example we have place it on the Desktop with the name Lab1.jar, as shown below After selecting Finish we will have the file Lab1.jar on the desktop. If just double click on it our application will run on the frame as shown before. The importance of this approach is that you can run this jar file in any machine that has java and it will run perfectly. 3. Handling images in Applications: There is a very important consideration to make here when dealing with images. While applets can read images rather simply from the bin folder, as you will learn in class using the img = getimage( getcodebase( ), "imgfile.jpg" ); command. The

31 case of Applications is different in this case you will have to change the previous line of code by the following one: img = Toolkit.getDefaultToolkit().getImage("imgFile.jpg"); Notice also that the location of the imgfile.jpg will have to be placed outside the bin folder and not inside otherwise the image will not be found 4. Handling Sounds in Applications: Later in the course you will also learn to add sound to your programs using the s = getaudioclip(getcodebase(),"soundfile.wav"); Applet command. Again for the case of Application programs this will have to be changed to a more obscure code as follows: try{ File myfile = new File("soundFile.wav"); s = JApplet.newAudioClip(myFile.toURI().toURL()); //Or s = JApplet.newAudioClip(myFile.toURL()); } catch (Exception e) {} Again note also that the location of the soundfile.wav will have to be placed outside the bin folder and not inside otherwise the image will not be found. BUT for the time being do not worry about this last piece of code yet. However, it is important to note that you may be required to turn both the jar file and the source java later in the course using Turnin. This is done by compressing both file in a single.zip file. 31

32 VII. Working remotely on your own computers Get and install java from the site Then install Eclipse version OXYGEN. Eclipse provides the development environment for writing and testing Java code. For Windows users Eclipse use the new installer guide For Mac user you can install directly fro the eclipse site 2. Get and install TURNIN (also see the Course Policies document). If you are connected to the Internet (and have Java installed on your machine) you should be able to run the TURNIN program and submit.java files from remote locations. 3. You should be able to access your W:\wwwpub remotely (to place applets on the web for viewing) in one of two ways. a. From a browser access your W: drive by going to and login with your TCU username and password. You should get a screen similar to the left window shown below. Double-click on a directory to navigate though the directory structure (eg., into WWWPUB\LABx). Use the Browse button to find the files (probably on your local C: drive) that you wish to upload (classes directory and LABx.html file). b. Or by using an FTP client that supports SSH, such as Core FTP Lite for Windows machines or FETCH for Macs. (Go to for a free download of CoreFTP Lite.). Run CoreFTP. From the Sites menu select Site Manager and setup as shown in the window below. Provide your TCU username and password.

33 33 When you press Connect and a connection is established you should see a screen similar to the window below. Navigate to find the files or directories you want to move (Source) in the left pane and the location where you want to place them (Destination) in the right pane (shown below). Then simply press the appropriate blue arrow to start the transfer. 4. ******* ALWAYS verify the transfer. ********** From Internet Explorer access (provide your username) and click on the lab you just transferred. You should see your applet run.

34 VIII. Using Eclipse 34 So far we have only used a small portion of the facilities of the Eclipse IDE. Gain more familiarity with the IDE by using the various facilities available. Here we explore some of them. Remember always to BACK UP YOUR SOURCE FILES outside of Eclipse to make sure you always have a way to get back if for some unexpected reason your lose some files while testing the IDE. 1. Refreshing and cleaning a project. Although most of the time you will be working within the IDE it may be possible that you modify a file of your workspace using a different editor. If this is the case when you go back to Eclipse be sure to select the project folder and using the right mouse button select the option Refresh, in this way the IDE will read the latest version in the workspace. See the following example: By using the Right Mouse Button you have access to various functions Among them the Refresh updates the selected folder for any external modifications Using the Right Mouse Button you have access to various functions You can run your program, selecting the Run option When a project has been modify externally in its source or object code it is a good practice to clean the object code and rebuild it. This is done by selecting the option Project Clean of the menu bar as shown below

35 35 From the Main Menu select The Clean option of Project Note that the Build Automatically Is checked so that the program is recompiled after the clean or any later modification is performed 2. Exporting a project using a Jar. In Java it is customary to wrap all the object class into one single compressed file, similar to a zip file. In Java these files are called JAR files (Java Archived Resources). Any project can be turned into a Jar using the export facilities available in Eclipse. Use the Right Mouse Button to select the option Export and follow the sequence of windows, as presented below:

36 Select the export Java folder And then the Jar file 36 Name the jar file, in this case as an example Lab0Project.jar Continue selecting Next until you get to the Finish and Eclipse will generate a JAR file that will be located in the project s workspace. The JAR file contains all the necessary file to run your program, for the case of Applets, you will change the html call to specify the location on the desired applet, For example in this case the new html code will have the following applet clause: <applet archive='lab0project.jar' code="lab0.class" width=200 height=200></applet> Note that in this case the file is located in the archive named Lab0Project.jar

37 3. Documenting your code using JavaDoc 37 In any programming language it is important to document your work. For the case of Java we use the double slash ( e.g. // ) for inline comments and the /** */ for paragraph documentation. Assume we have a program that determines the Julian Number for a given date, the method to compute the number requires as parameters the day, the month and the year and returns a unique sequential number that identifies that date. A possible documentation for the method would look as follows: /** * This method computes the Julian Number day (e.g. 1 to 31 ) month ( e.g. 1 to 12 ) year ( e.g. an positive integer ) Julian Number */ public int calcjdn( int day, int month, int year) { // here the code for the Julian Number method // to do instructions. } But Java goes further in the documentation because it allows us to generate an standardized webpage documentation named the (Application User Interface) that we can use to learn how to use the specific Java class. For the sake of practice using Eclipse using the Right Button select the export option of a given project as we did before; however this time select the option export as Javadoc in the corresponding window: Exporting using the Javadoc option of the Java folder Follow the wizard windows by selecting Next, you will need to provide a name for the folder where you want the documentation to be placed or simple accept the default doc folder. Continue until you get to the Finish option.

38 38 Once you have finished you will find that you have a new folder with the documentation of the program. This folder contains the API documentation of your class and you can select the index.html file to start the navigation using any browser as follows: Select the index.html file of the doc folder to review the documentation of the Lab0 class In order to get meaningful and useful information in the API it is your responsibility to document your source code using the /** */ standards described before. As your get a better understanding of the Java language you will notice that only the public methods are documented in the API. Look for the Fahrenheit Applet in the webpage of the course for a complete example of proper documentation of Java Programs.

39 4. Converting an Applet into a stand alone Application. 39 Another way to run an JApplet is to fully convert it into an Application, this is similar to what we did in section VI, but a bit more complete since the JApplet is transformed into an application So far we have been working with applets that run using a web browser to start the application. Here we provide a short introduction to this process. Java also allows to generate stand alone programs that run as an application triggered from a local machine. Furthermore using the concept of a Jar we can create clickable applications that run by a simple click. This might not sound of little relevance, however bear in mind that we can generate the program in any machine (e.g. a Mac) and run the program flawlessly in a different machine (e.g. a WinXP) with no reprogramming or recompilation. This is an important benefit of Java. 4.1 To show how we do this in Eclipse let us convert the Lab1Project by select New Project from the File menu. Select General/Java Application and press Next. Let us call the project Lab1App. 4.2 Create a new Class for this project and named it Lab1main. The Eclipse IDE will show you a set of windows to do so.

40 40 a. Let us now edit this class with the following code that resembles the code we used for the Lab1Applet, with some important changes we discuss below. import java.awt.*; public class Lab1main extends Frame { public Button btnstop = new Button("STOP"); public Lab1main() { add(btnstop); this.pack(); this.setvisible(true); } public static void main(string[ ] args) { new Lab1main(); } // trigger class }

41 41 This code changes the Applet into a Java Application. And so rather than using an Applet we will use a Frame to pop up a window. Also rather than the method init() we have a new method named as the class itself, Lab1main. Note that we have added two lines of code: this.pack(); this.setvisible(true); they are needed in order make a visible pop up window in the case of Java Applications, Applets are displayed directly by the web browser and that is why we did not added these lines in the previous case. Finally we need to create a method that will trigger the Application, this is the second method in the code and must be named main(). We will discuss in class all the details of it when we discuss applications. In any case, provided that you have copied verbatim the code the IDE should look as follows: Extra lines of code needed Main method required to trigger the applicatio Run the program as a Java Application and you will be able to run this method, by selecting the option as shown above. The outcome of this is shown below:

42 42 Pop up frame displaying the Button Note that the performance of this applet is similar to the performance when we run the Lab1Applet. However we did not require the web browser to trigger the program. We can now convert this program into a Jar file in order to run it outside the IDE. For this you should follow the steps presented in section VII.2 of this guide. As we gain more familiarity with Java we will introduce other important features required in a Frame to be fully compatible with an Applet. Such as adding more classes and controlling the event of the window using a WindowListener, adding extra imports and many more. 5. Running the Debugger using JApplets By now you have realized that tracing the execution of a program is a rather important part of your work as a programmer. This task is generally known as debugging a program, i.e. getting rid of the logical bugs you might have made. A simple solution to it is the use of messages sent to the console by means of the System.out.println() method. However a more complete help is to use the tools provided by the Eclipse Debugger. In this section we provide a brief introduction to let you get acquainted with the tool available so that you might learn to use it when you have a more complex programming task. In this guide we will use the following code, but we invite you to use any code of your previous labs to one feel more familiar with.

43 43 To start the debugging we must select the instructions we want to trace, this is done by adding breakpoints in the blue left side of source window where we want the program to pause. A breakpoint is a location in your source code that will halt execution so that you can view the information about a program's state. To do this right-click along the left side of the Java editor on the line of code you wish to break on, (Also, double-clicking on the left side of the editor will create a breakpoint.). See in the following figure how to toggle a breakpoint. After you do it you will see the breakpoint (a blue dot) and if you pass the mouse over it you

44 get the following message. To turn it off double click it again. 44 We are now ready to run the debugger. So far you have use the command Run As.. Java Applet; but now we will use the command below in the options Debug As.. Java Applet, as shown in the figure When you run the debugger your window perspective will change from that of java running to debugging, this in order to provide you with other useful windows in the process. You may get a message from Eclipse telling you about it, as shown below In any case the new look of the perspective is similar to the one shown here:

45 45 Let us pay attention to the debugging buttons located at the right side of the menu of the debug window: This window shows the live stack trace of methods. When working with JApplet we are at the highest stack level object so in order to get down to a breakpoint select couple times the Resume button until the code of your program is displayed in the source window showing the temporary halt at the selected breakpoint. Looking at the Variables Window you will see the values currently assigned to them. In our example we see that num1 = 9 and mys = Hello as shown below:

46 If you keep selecting the resume icon you will move to the next breakpoint. Note that if the breakpoint is located in another class i.e. another program, the debugger will jump into it and deliver the values of the objects associated. In the case of the example we present here a for loop and the values associated with it as it the debugger program runs through it 46 The debugger also has two stepping buttons: Step Over and Step Into. Step over takes you to the next instruction within the code and Step Into jumps into the code when a method is called. Again you can see assigned value for the variables changing accordingly. As you can imagine, knowing the values of your variables eliminates the need for using System.out.println() statements throughout your code. Finally the Stop button stops the execution of the debugging. You can debug again or go back to the regular java execution by using the Run As command. Note that you can always go back to the Java perspective by selecting from the Window Menu in eclipse the desired perspective.

47 47 A useful aspect during debugging is the fact that you can change the internal assigned values of your program, for example assume we change the value of variable num2 in the variables window. Initially assigned to 4.0 and we change it to 6.0 if we step over the code using we will get to the line if (num2>5) System.out.println( " Value changed for num2 " + num2 ); this line should not have not been executed, but since we have changed its value we will get in the console the message: value changed for num There are many other features available for debugging such as establishing watchpoints. We have provided only an introduction. We recommend you look at the following informative links: