Why is jar file required to execute a MR code instead of class file

Question

While executing MapReduce code I am wondering why we need a jar file and cannot use a class file to execute MR code in Hadoop? An also whywe donot use java keyword while executing a Java code in Hadoop?

Answer 1

We use hadoop keyword to invoke the hadoop script.

The benefits of using jar here are: The jar required to run the code which are present in Hadoop lib directory are bundled together in the jar file. The configuration files which are required for the MR code execution are also bundled here in the jar file.

So, while using jar all of this things are bundled together and are execution ready. But using class if you are executing the jar you have to add all the required jars & configuration files separately.