kantri yama

Hi,

I need to implement a storage structure(inverted index) for information retrieval project. For each keyword, I need to store the document ID in which it is present and position of occurrences. For ex

inverted index :
a->[doc 1, (1,2,4)], [doc2, (2)]
b->[doc 1, (3)], [doc2, (3)]
c->[doc 2, (1)]

i.e 'a' is present in doc 1 at 1,2,and 4 positions and in doc 2 at 2nd position. I am puzzled about how to implement hashmap for this index. I couldn't get an idea about how to implement [doc 1, (1,2,4)] as one part, and [doc2, (2)] as another part using multiple values for each key. Please help me.