After a painful searching for code completion functionaly for vim, I finally
resorted to eclim.
And I added one more line in ~/.vim/plugin/eclim.vim:
source ~/.vim/ftplugin/java/my_config.vim
since it will be overrided by eclim.
Added doc generator vimdoclet.
Added .gitignore.
Added config for ant.
Committed config for java.
Added neocomplete plugin for vim.

It works like magic!!!