Just enough Java for Hadoop [closed]

Answer 1

Learning "just enough" Java is learning Java. Either you learn all the core principles and language design decisions, or you suffer along making easily avoidable mistakes. Considering that you already know how to program, a lot of the information can be skimmed (with an eye for where it differs from other languages you are intimately familiar).

so you need to learn:

1. How to get started
2. The language itself
3. The core, essential classes
4. The major Collections

And if you don't have a build framework in place, how to package your compiled code.

Beyond that, nearly every other item you might need to learn depends heavily on what you intend to do. Don't discount the on-line tutorials from Oracle/Sun, they are quite good (compared to other online tutorials).

Answer 2

Most of the stuff should be pretty familiar to you. I'd just download eclipse and google a tutorial site. Familiarize yourself with classloading, keywords. One tricky thing a lot of C++ guys run into is how to run a java app so that it finds its library classes(sort of analogous to dynamic linking). Learn the difference between the JRE and JDK. If you can get a few hello world type apps working you ought to be able to get a start on hadoop if you follow the tutorials.

Answer 3

Here is the quickstart for all you will need I suggest Eclipse (java) to start working, see this for that

Answer 4

You dont need to learn java to use hadoop.

You need to know linux to installand configure hadoop

then you can write your map reduce jobs using the stream line api on any language which understand standard input/output

further you can do more complex map reduce using other libraries like hive etc

even other components of hadoop like hbase/ cassandra also has clients on most of the languages

Answer 5

• Take it easy, learning Java could be pleasant and fast if you already know C++

  Buy these two books:

  1. The JavaTM Programming Language, (4th Edition) Ken Arnold, James Gosling, Davis Holmes
  2. Effective Java (2nd Edition), Joshua Bosh

You will soon be mastering Java, You will not regret. Good Luck.

Answer 6

I don't know how familiar are you with other higher level programming languages. Garbage collection is an important function in Java. It would be important to read a bit about the GC in your VM of choice.

Besides the obvious packages, check out the java.util packages for the collection framework. You might want to check out the source of some classes. I suggest HashMap to get the idea of the computing/memory cost of these operations.

Java likes to use streams instead of buffers when processing large amounts of data. That may take some time getting used to.

Java has no unsigned types. Depending on the packets of data you need to process at once you can either use larger variables and streight arythetics (if we're talking about relatively small packets), or you have to (b[i] & 0xff) every time you read for example unsigned bytes. Also note that Java uses network byte order (msbf) when serializing multibyte numbers.

The most beloved design patterns by the API are Singleton, Decorator and Factory. Check the source of JFC itself for best practices, how these patterns are achieved in the language.

... and you can still post more concrete questions on SO :)