NullPointerException while using put method of HashMap

Where is datamap initialised ? It's always null.

To clarify, you declare the variable and set it to null. But you need to instantiate a new Map, whether it's a HashMap or similar.

e.g.

datamap = new HashMap();

(leaving aside generics etc.)

Well, there are three objects accessed on that line. If nextLine[0] and nextLine[6] aren't null, because the println call above worked, then that leaves dataMap. Did you do dataMap = new HashMap(); somwehere?

HashMap<String, String> dataMap = new HashMap<String,String>();

Your dataMap variable isn't initialized at this point. You should be getting a compiler warning about that.

dataMap is declared but not initialized. It can be initialized with

datamap = new HashMap();