What are the prerequisite to learn Hadoop?
There is no strict prerequisite to start learning Hadoop.
However, if you want to become an expert in Hadoop and make an excellent career, you should have at least basic knowledge of Java and Linux.
Don't have any idea on Java and Linux? - No worries, you still can start learning Hadoop. The best way would be parallelly spend few hours on learning java and Linux too.
We will explain the Java/Linux aspect in more details in next paragraphs.
Is Java required to learn Hadoop?
Knowing Java is an added advantage, but Java is not strictly a prerequisite for working with Hadoop.
Let us deep dive on these 2 scenarios.
Why Java is not strictly a prerequisite:
Tools like Hive and Pig that are built on top of Hadoop offer their own high-level languages for working with data on your cluster. If you want to write your own MapReduce code, you can do so in any language (e.g. Perl, Python, Ruby, C, etc.) that supports reading from standard input and writing to standard output with Hadoop Streaming.
Also, there are high level abstractions provided by Apache frameworks like Pig and Hive for which familiarity of Java is not required. Pig can be programmed in Pig Latin and Hive can be programmed using HiveQL. Both of these programs will be automatically converted to MapReduce programs in Java.