[HADOOP-13320] Fix arguments check in documentation for WordCount v2.0

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.8.0, 3.0.0-alpha1
• Component/s: documentation
• Hadoop Flags: Reviewed
• Assignee: niccolo becchi
• Reporter: niccolo becchi
• Created: 24/Jun/16 13:40
• Updated: 30/Aug/16 01:13
• Resolved: 07/Jul/16 22:55

Description

This issue is affecting the documentation page, so the code is not covered by any tests. It's actually visible on the page:
https://hadoop.apache.org/docs/current/hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduceTutorial.html#Example:_WordCount_v2.0
On the Example: WordCount v2.0

The actual arguments check is wrong, as it's never printing the message of the correct usage. So, running the code with no parameters, as in the following example:

yarn jar /var/tmp/WordCount.jar task0.WordCount2

I have got the following exception message in output:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at java.util.ArrayList.rangeCheck(ArrayList.java:635)
    at java.util.ArrayList.get(ArrayList.java:411)
    at task0.WordCount2.main(WordCount2.java:131)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:136)

Intead than the expected friendly message:

 Usage: wordcount <in> <out> [-skip skipPatternFile]

Issue Links

• links to: GitHub Pull Request #108