Let's begin the lab by collecting a little information from you. (If you missed your lab session, please take a few minutes to fill out the survey on your own. Your answers will help us tune the course so that it works better for you!)

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Overview

Is Eclipse Required for this Course?

How to Set Up Eclipse

• In the Unix Labs, eclipse 3.0 is with Java 1.5 is already installed.
• For your home computers you can download Eclipse from http://www.eclipse.org/downloads/index.php. You will need to download the version for Java Developers, not the one for Java EE Developers.

A First Taste

1. Start Eclipse
2. Since this is the first time you're running Eclipse, you'll be asked where you want your "workspace" to live. Accepting the default is fine.
3. Since this is a new workspace, Eclipse will begin by displaying a "Welcome" screen.
• To get a first impression of how Eclipse works, click on the "Tutorials" button on the welcome screen, choose the first tutorial (Hello World), and follow the instructionsto create a complete (though tiny) Java program and run it.
4. Now let's do the same thing again with a more interesting program.
• Close the Welcome screen if you have it open.
• Choose File -> New -> Java Project from the menu, to create a new project in your workspace. (A project is a collection of source files, documentation, and other related files. You should create a separate project for each homework and lab.)
  • Call the new project HW2.
  • Instead of "Create new project in workspace," select "Create project from existing source."
  • Click the Browse button and navigate to the directory where your solution to Homework 2 is stored.
    • If your completed HW2 assignment is not on the machine you're working on right now, you can just re-download the files hw2.jar and Tester.java from the course homework page.
  • Click Finish to create and populate the project.
• In the "Package Explorer" (the pane on the left of the screen) you'll see your new project displayed with a small red X. This means that there is an error somewhere. To see where the error is, open the project (by double-clicking on it, or by clicking the small triangle symbol to its left). Keep opening things until you can see the individual classes in the project. If you look at one of these (by double-clicking it), you'll see that the errors are coming from places where the code is referring to resources that we provided for you in the hw2.jar file. We haven't told Eclipse to look in this file yet.
  • Go to the Project Properties screen (menu Project -> Properties). Choose Java Build Path; then click the "Add external Jars" button. Navigate to the hw2.jar file on your disk and click OK (twice).
  • Look back at the classes in your HW2 project and observe that the small Xs are gone. If your HW2 code was in a working state when we started, there should be no Xs left.
• To run your program, do this:
  • From the menu, choose Run -> Run.
  • Click Java Application.
  • A "Console" window should now open and show you the results of running the Tester—just the same as what you would have seen if you had run it from a command line.
5. Try adding a couple of new classes, by doing File -> New -> Class. (For example, try adding a Merchant class that extends the class Character and overrides one of its methods in some simple way.)
   • In the dialog that opens, you must provide the name of the new class, but that's the only bit that's required.

Learning More

1. The "Welcome Screen" that we skipped at the beginning is an excellent starting point for exploring further. You can get it back by choosing "Welcome" from the Help menu. Spend a few minutes now skimming the Overview section.

More Information

Perspectives

• The first time you run it, you will be asked several questions about setting up your workspace. We suggest keeping the default settings. Once you complete the initial setup, you will be introduced with a Welcome screen, which you can skip.
• Eclipse is designed around views called perspectives. The first time you start Eclipse, you will be in "Resource perspective". We will also be seeing Java and Debug perspectives in this tutorial.

Browsing a Project

• If you expand a project in the Package Explorer (the pane on the left of the screen), you will see the packages included in the project and the libraries it uses. The "default" package contains every class that is not included in any other package.
• To add libraries to your project that you will use such as provided jar files, go to Project Properties by doing a right click on project name. From properties screen, go to Java Build Path. Here you can add all required libraries.
• As you expand a source file, you will see a list of its classes, and a list of methods in each class and so on. This can help you lookup a method quickly if needed. You can also use the outline pane as you are writing code to have a quick list of accessible methods.
• To create a class or interface in a project, you can choose File -> New -> Class or File -> New ->Interface. If your class is extending another class or implementing an interface, Eclipse will automatically place method declarations for you.

Helpful Features While Coding in the Code Pane:

• Auto complete in methods: As you write your code, you will be presented with a list of possible choices.
• Error checking as you type: Errors will be underlined red in your code. One thing to note here, eclipse will mark your code incorrect as you are typing it. Once you complete the line, it should go away unless your code is really incorrect.
• Easy commenting: If you're on a method signature, you can press Alt+Shift+J to insert javadoc comments.
• Auto indent any piece of code by selecting it and pressing Ctrl+I.
• Auto-compile: your files will be compiled automatically each time you save them. If an error exists in your files, you will see a red mark by the file name in Package Explorer. Also, the Error Pane located at the bottom will give you a list of errors occurred during last compilation. You can double click an error to go to its location.

Running your code

• Unlike DrJava, eclipse is only able to execute classes with main methods. To do so, open the Context Menu on the file name and choose Run As -> Java Application. You will see the output in Console pane. Alternatively, you can press Alt+Shift+X, J to run the file that is currently being edited.
• If you want to have more options such as sending arguments, you can choose Run... instead of Java Application.

Debugging

1. Create a new project and create a new class called Driver in the project.
2. Copy the contents of the Driver.java file to that class (or alternatively copy Driver.java to the directory of the project and refresh the project). Do the same for Ticket and MovieTicket.
3. You will set breakpoints to suspend the execution of your program. To add a breakpoint to any line in the code, press Ctrl+Shift+B while you are on that line. (Alternatively, choose Run -> Toggle Breakpoint from the menu.) For our purposes, add a breakpoint to the first line of the main method in Driver.
4. For debugging to work, you have to run your program in Debug mode. To do that you can press Alt+Shift+D, J or choose Debug As -> Java Application from the context menu. Once you run your program, it will execute up to first breakpoint it encounters and stop at that point, Eclipse will ask you to switch to Debug perspective automatically as it happens.
5. Debug perspective contains a call stack at the top left corner, a summary of variables in top right corner. You can also get a list of breakpoints at the same place. At the bottom, you can see the console which will show any output.
6. Our aim will be to analyze the values of various objects to see what is happening to them as the program executes. There are several ways to do this:
• You can highlight the name of an object in the code panel and choose Inspect from the context menu. This will open a small window listing all its instance variables.
• From the variables panel at the top, you can expand the name of an object to get a list of its instance variables.
• As the last option, you can add an expression to be watched. In order to do that, you have to open Expressions window by choosing Window -> Show View -> Expressions. This will open a new tab on top right corner. You can right click anywhere on that tab and choose Add Watch Expression, any expression you type here will be watched throughout the debugging process. For example you can type audience[3] to watch the fourth element of the audience array. Note that this only works as long as the object being watched is in scope.
7. You also have different options to continue running your code. You can access the buttons explained below on the Debug pane.
• Resume (F8): Resumes your program until the next breakpoint or until the end of execution.
• Step Into (F5): Only executes one line in the program. If the current line is a method call, it will enter that method.
• Step Over (F6): Only executes one line in the program. If the current line is a method call, it completes the execution of that method and goes to the next line. It doesn't go into the called method like Step Into.
• At any time, you can terminate the execution of the program by pressing Terminate button.