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If You Got NoClassDefFoundError Error

Error: Could not find or load main class xxxxx.helloworld.HelloWorld
Caused by: java.lang.NoClassDefFoundError: com/godtsoft/diyjava/DIYWindow

This message happens if the DIYWindow was added to the Modulepath instead of the Classpath. Eclipse then cannot find DIYWindow. To fix this:

Right click on the Hello World Project in the Package Explorer of Eclipse and choose Build Path / Configure Build Path...

If DIYJava.jar is in the Modulepath, select it and click Remove.

Now, click Classpath and click Add External JARs...

Browse to where you saved the DIYJava.jar file and select DIYJava.jar. DIYJava.jar should now be in your classpath.

Click Apply and Close.

Now when you run your HelloWorld program it should be able to find the HelloWorld class and you should no longer get that error.

You Don't Need to Create for Your Project...

Modules are a new packaging option introduced after these books were written. None of the projects in these books use modules. If you see a window to create a file, click Don't create.

  1. Click Don't Create.
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    If You Were Unable to Add DIYJava.jar as the External JAR File...

    There is a problem with some versions of Eclipse. After completing Lesson 1.1, if you do not see the DIYJava.jar file in the Package Explorer window as shown here, follow the steps below to add DIYJava.jar to the project.

    Add DIYJava.jar as an External JAR file to an existing project:

    1. Right click on the existing project in Package Explorer.
    2. Select Build Path.
    3. Select Add External Archives...
    4. Browse to and select DIYJava.jar, which you installed in your Java work folder, and click Open.
    5. Click Finish.

    The Package Explorer pane should now show the added JAR file (DIYJava.jar).

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    If Eclipse Can't Find the Latest Installed JDK.

    This error occurs if the JAVA_HOME System Environment Variable is not set up correctly. To set the JAVA_HOME and PATH System Environment Variables, do the following:

    • Go to Start / Windows System / Control Panel, click View by:, and select Large icons.
    • Click System / About.
    • Scroll down and click the Advanced system settings link.
    • Click Advanced / Environment Variables....
    • Under System variables, if JAVA_HOME exists, select it and click Edit. If JAVA_HOME does not exist, click New.
    • Set JAVA_HOME to the directory of the newly installed JDK and click OK. For example, C:\Program Files\Java\jdk-
    • Under System variables, select PATH and click Edit / New. Add %JAVA_HOME%\bin to the beginning of the list and click OK.
    • Under User variables, if Path exists, select Path and click Edit. Add %JAVA_HOME%\bin to the beginning of the list and click OK. If Path doesn't exist, don't add it. It should automatically default for your user to use the system variable PATH.
    • Click OK to close the System Properties window.
    • Close the Control Panel window.

    Next, make sure Eclipse uses the latest JDK.

    • Restart Eclipse so it uses the latest JAVA_HOME System Environment Variable.
    • Click Window / Preferences /Java / Installed JREs.
    • Select the newest JDK in the list.
    • Click Apply and Close.

    If the newest JDK is not in the list of Installed JREs, add the new JDK to the list.

    • In Eclipse, click Window / Preferences / Java / Installed JREs.
    • Click Add to get to the Add JRE window.
    • Choose to add a Standard VM and click Next.
    • Click Directory... to get to the JDK folder that contains the bin folder. It may be something like C:\Program Files\Java\jdk- Click Select Folder after you select the folder.
    • Click Finish.
    • Select the JDK you just added as the new default JRE.
    • Click Apply and Close.

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    The Do-It-Yourself Java Games Series of Books

    Learn more about the Do-It-Yourself Java Games series of books. Learn why these books were written, why learn computer programming, and why Java. Learn how these books are organized, why they were written as electronic books, and what's next.

    The books currently available in the series:

    1. Do-It-Yourself Java Games: An Introduction to Java Computer Programming - Learn More.
    2. More Do-It-Yourself Java Games: An Introduction to Java Graphics and Event-Driven Programming - Learn More.
    3. Advanced Do-It-Yourself Java Games: An Introduction to Java Threads and Animated Video Games - Learn More.
    4. Do-It-Yourself Multiplayer Java Games: An Introduction to Java Sockets and Internet-Based Games - Learn More.