错误“找不到主类”

Question

All,

My classpath has been set to the following folder:

CLASSPATH = .;C:\Program Files\Java\jdk1.6.0_21\bin;C:\Program Files\Java\jdk1.6.0_21\bin\project

All my java files and class files are under project folder listed in CLASSPATH .

Yet I am getting the following error while running a DriverClass in project folder:

C:\Program Files\Java\jdk1.6.0_21\bin\project>java DriverClass
Exception in thread "main" java.lang.NoClassDefFoundError: DriverClass (wrong name: project/DriverClass)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(Unknown Source)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: DriverClass.  Program will exit.

Can anyone please help me understand the reason here?

Answer 1

You're inside the package. You should be sitting in the package root. Go one folder up.

cd ..

Then reexecute it using java project.DriverClass .

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That said, you should prefer not to use the CLASSPATH environment variable. Yours is currently also invalid. There are spaces in unquoted pathnames. Also, the JDK/bin folder isn't supposed to go in the classpath. Just use the -cp argument like java -cp . project.DriverClass java -cp . project.DriverClass (while sitting in the package root folder).

Answer 2

Try:

C:\Program Files\Java\jdk1.6.0_21\bin>java project.DriverClass

assuming your package is project

Answer 3

After compiling if we get a main class not found error, It is simple try this set classpath=%classpath%;.; type this in cmd and run it..problem will be resolved