The Java API offers possibility to submit multiple Hadoop job in one source file. A job can be submitted either using

• job.waitForCompletion – the job is submitted and the method waits for it to finish (successfully or not).
• job.submit – the job is submitted and the method immediately returns. In this case, the state of the submitted job can be accessed using job.isComplete and job.isSuccessful

Improve the sorting exercise to handle nonuniform keys distribution. As in the Perl solution, run two Hadoop jobs (using one Java source file) – first samples the input and creates separator, second does the real sorting.

Improve the inverted index creation exercise, such that

1. in the first job, create a list of unique document names. Number the documents using the order in this list.
2. in the second job, create for each word sorted list of DocWithOccurences<IntWritable>, where the document is identified by its number (contrary to the previous exercise, where Text was used to identify the document).

Implement the K-means clustering exercise in Java. Instead of an controlling script, use the Java class itself to execute the Hadoop job as many times as necessary.