title: Eclipse MapReduce Error: UnModifiableMap
body: <p>so I'm new to Hadoop and MapReduce and am attempting to create a simple WordCount program. When running it however, I run into an error:</p>
  
  <pre><code>Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/collections/map/UnmodifiableMap
  at org.apache.hadoop.conf.Configuration$DeprecationContext.&lt;init&gt;(Configuration.java:409)
  at org.apache.hadoop.conf.Configuration.&lt;clinit&gt;(Configuration.java:448)
  at com.Cameron.WordCount.main(WordCount.java:51)
  Caused by: java.lang.ClassNotFoundException: org.apache.commons.collections.map.UnmodifiableMap
  at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
  at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
  ... 3 more
  </code></pre>
  
  <p>I've had a look around online and the cause seems to be the fact that the Commons Collection JAR isn't included in the build path, although with mine it is and I'm still getting the error. I've tried cleaning the project and restarting Eclipse to no avail, so any help would be greatly appreciated. My build path configuration is as follows:</p>
  
  <pre><code>commons-collections4-4.1.jar
  commons-lang-2.6.jar
  commons-logging-1.2.jar
  guava-11.0.2.jar
  hadoop-common-2.7.2.jar
  hadoop-mapreduce-client-core-2.7.2.jar
  JRE System Library [JavaSE-1.7]
  </code></pre>