在classpath中使用.jar中的类

Question

when I try to use some class, for example Layout, in swt.jar by cmd it complains me about not having it, this is the message error:

Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/swt/widgets/Layout

The weird thing is, swt.jar is in \\ext directory and my CLASSPATH is C:\\Program Files\\Java\\jdk1.6.0_26\\jre\\lib\\ext

When I create a new project in eclipse there's no problem, all imports from this jar works fine, but on cmd I'm getting this error.

Help me please!

Answer 1

You need to set the classpath till the Jar File , to use a class under that Jar File

C:\Program Files\Java\jdk1.6.0_26\jre\lib\ext\swt.jar

Just a suggestion: - Don't put your Jar files in the ext directory. Put it somewhere else.

As far as Eclipse is concerned, it does not uses the System Classpath set in the environment variable. You should put the Jar File in a lib directory under your project while using in Eclipse and add the Jar File to your BuildPath.

Answer 2

You're learning a hard lesson: IDEs, including Eclipse, and Java EE app servers, like Tomcat, pay no attention to any environment variables like CLASSPATH.

I don't think a JAR like swt.jar belongs in the jre/lib/ext directory. That should only be for JVM extensions from Oracle.

You should add that to your project /lib directory, along with all other 3rd party JARs, and set CLASSPATH in Eclipse and startup scripts properly.