Parsing Files From Directories And Store Them In Hashmap

I have a query regarding parsing a directory, its subdirectories and files of directories. i am using File Object to load absolutepath of main directory and checking file is a directory or file but not geeting exact solution what i want. Suppose directory structure is D:TestPC

PC is a directory and have 2 files test.txt test1.txt and one directory
PC1 directory contains 2 directories PC2 ,PC3 and each PC2 and PC3 have some files.

Now my query is : i want to store each directory in HashMap and its files corresponding to its directory. E.g.:

D:TestPC ---> D:TestPC est1.txt , D:TestPC est2.txt
D:TestPCPC1---> Null
D:TestPCPC1PC2 --->D:TestPCPC1PC2 est1.txt, D:TestPCPC1PC2 est2.txt

like this, where first directory path as key and files are its values.