title: ClassNotFoundException with SIGAR API
body: <p>I'm trying to work with the SIGAR API, and I added the external jar "sigar.jar" to my Build Path eclipse project. 
  It compiles with no problem, but when I try to run the main class, that only does :</p>
  
  <p>Cpu cpu = new Cpu();</p>
  
  <p>it gives me this error:</p>
  
  <pre><code>    [java] Exception in thread "main" java.lang.NoClassDefFoundError: org/hyperic/sigar/Cpu
   [java]     at pt.client.User.main(User.java:90)
   [java] Caused by: java.lang.ClassNotFoundException: org.hyperic.sigar.Cpu
   [java]     at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
   [java]     at java.security.AccessController.doPrivileged(Native Method)
   [java]     at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
   [java]     at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
   [java]     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
   [java]     at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
   [java]     ... 1 more
   [java] Java Result: 1
  </code></pre>
  
  <p>What may be missing?</p>