Hadoop Combat---Problems and workarounds for Hadoop development

First on the correct run display:

Error 1: The variable is intwritable and is receiving longwritable, such as:

Reason, write more parameters reporter, such as:

Error 2: The array is out of bounds, such as:

Cause: The Combine class is set up, such as:

Error 3:nullpointerexception exception, such as:

Cause: The static variable is null and can be assigned, such as:

Error 4: Entering map, but unable to enter reduce, and direct map data output, and no error prompt
Cause: The new and older version of Hadoop is actually an instantiation exception, such as:

Error 5: Enter the main function, unable to enter the map, and will not enter reduce, and no error prompts
Cause: The new and old version of the problem, the specific will cause this problem, more to summarize:
Old version:

New version:

In a word, the Hadoop version is a problem!

Hadoop Combat---Problems and workarounds for Hadoop development