How do I run Java .class files?

java compilation
Skizz picture Skizz · Apr 22, 2011 · Viewed 203.4k times · Source

I've compiled a HelloWorld program, and I'm using the command prompt to run it. The .class file is named HelloWorld2.class

The file is located in C:\Users\Matt\workspace\HelloWorld2\bin Here's what I'm getting when I go to command prompt, and type "Java HelloWorld2" :

C:\Users\Matt>Java HelloWorld2
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld2
Caused by: java.lang.ClassNotFoundException: HelloWorld2
        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: HelloWorld2.  Program will exit.

I was expecting to see a HelloWorld printed out. What am I doing wrong? I have the JDK installed.

Answer

Isaac Truett picture Isaac Truett · Apr 22, 2011

You need to set the classpath to find your compiled class:

java -cp C:\Users\Matt\workspace\HelloWorld2\bin HelloWorld2

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