For Instructors

Objectives

• to familiarize you with the Metrowerks Codewarrior Programming Environment.
• to provide practice editing, compiling, running and revising a Java application.

Before Lab

Editing, Compiling, and Running a Java Program

Metrowerks Codewarrior is an integrated development environment (IDE) for Java, C++, and other languages. It combines software resources for editing, compiling and running programs. In this IDE Java programs consist of two parts:

• the Java code itself, which contains the text of your source program and
• a project, which contains the Java bytecode that will be executed when you run your program.

The Codewarrior project combines precompiled code from the Java class libraries with the code compiled from your Java source program, thereby increasing the functionality of your code. This lab will take you through the steps required to edit, compile, and run Java programs.

Step 0. Close all applications on your computer.

Close all applications that may be running on your computer in order to make as much memory as possible available to Codewarrior.

Step 1. Run the Metrowerks Codewarrior IDE

 Codewarrior IDE 4.0 is located in the Lab Applications folder.

  NOTE: Remember how to find this program because you're going to need it every week.

Step 2. Create the Lab1 project.

Once you have Codewarrior running, create a new project and configure it according to the following directions:

Click on the FILE menu option, then select NEW. Make sure the PROJECT tab is selected and enter the name of your project, "Lab1". The "Location" text box should indicate that your project will be stored on the desktop. In the project text area, double click on "JAVA Stationery". During this step, you should see something like the following window:

In the New Project window, click the "+" sign which is to the left of Java2. Select "Java Application" as the project type. During this step, you should see the following window:

After you save your project, Metrowerks will open a project window that should look something like this:


If this is NOT how your project looks, ask for help.

Step 3. Run the TrivialApplication Program.

To compile and run TrivialApplication.java choose the Run option from the Project menu. Codewarrior will compile the application into Java bytecode and then interpret the bytecode all in one step. As a result, something like the following Java Output window should appear on your desktop.

Java programs are run by the Metrowerks Java program, which is an implementation of the Java Virtual Machine. It's a good idea to remove the Java Output window when the program is finished running. To do so, click on the "go-away box" (Upper left corner of the window's title bar).

Step 4. Edit and Re-Run TrivialApplication

• Open the source code TrivialApplication.java by double clicking on its name in the project window. The program contains the following code:

     public class TrivialApplication {
        public static void main(String args[]) {
            System.out.println( "Hello World!" );
        }
     }
  

  To Do: Change "Hello World!" to some other message by editing the System.out.println() statement on line 3. Then re-run the program. Codewarrior will automatically save your changes.

• Notice that the name of the class in TrivialApplication.java is TrivialApplication. The rule in Java is that the Java source file must have EXACTLY the same name as the public class it contains.

  To Do: Change the name of the class in TrivialApplication.java to HelloWorld and then save the file and try to re-run the program.

  System Error:A system error will occur when Codewarrior tries to load the TrivialApplication class into memory but can't find it. This time you should get an error message in the Java Output window which says:

  Can't find class TrivialApplication
  

  You can fix this error by changing the class' name back to TrivialApplication (spelled EXACTLY that way) and then saving and re-running the program.

  NOTE: If a Java program's file name does not match the name of the public class that is defined within the file, it won't run properly.

• When we write our own Java source code we will usually rename TrivialApplication and then edit the source code. Try this! Change the name of the public class in TrivialApplication.java to HelloWorld and then rename the file to HelloWorld.java (using the file Save As option in the File menu). Then click on the Targets option in the project window and change the name of the Java Target to HelloWorld. In all Java applications, the name of the target class, must match the name of the public class in your main Java program. Then run the program and make sure it works correctly. Ask for help if any kind of error occurs.

• A syntax error is an error generated by the compiler when it cannot correctly parse your source program. There are lots of ways to generate a syntax error: misspelling Java keywords, forgetting to declare a variable before using it, misspelling a previously declared identifier and forgetting a semincolon at the end of a statement.

  To do: Delete the semicolon after the System.out.println() statement and then re-run the program.

  Syntax Error:This time you should get an error message in the Errors and Warning window which says:

     Error: ';' expected
     TrivialApplication.java line 6 System.out.println("Hello World")
  

Lab Checkout