You can compile and run a MapReduce program written in Java on our Hadoop cluster. Below is an example of how to do so. You can get the WordCount.java file from HDFS:
hdfs dfs -get /var/examples/WordCount.java
Then run the following:
javac -cp `hadoop classpath` WordCount.java jar cf wc.jar WordCount*.class hadoop jar wc.jar WordCount \ /var/examples/romeojuliet.txt /user/<your_uniqname>/wc-output
To view the output:
hdfs dfs -cat /user/<your_uniqname>/wc-output/part-r-00000