noobie question on hadoop's NoClassDefFoundError

[felix gao]

I wrote a simple code in my eclipse as

Text t = new Text("hadoop");
System.out.println((char)t.charAt(2));

when I try to run this I got

Exception in thread "main" java.lang.NoClassDefFoundError:
org/apache/commons/logging/LogFactory
    at org.apache.hadoop.io.Text.<clinit>(Text.java:49)
    at com.example.io.WritableIOExample.main(WritableIOExample.java:44)
Caused by: java.lang.ClassNotFoundException:
org.apache.commons.logging.LogFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
    ... 2 more

The library used are Haddop 0.20.1 and log4j-1.2.15

Thanks for helping