Using java File doesn't look like an option, the path separator doesn't cause the unzip to extract the directories, but instead creates each file named with the directory name, ie; 
-rwxr-xr-x  1 doswell is-staff   3882 2013-10-27 07:54 share\doc\api\lib\trait_diagram.png
-rwxr-xr-x  1 doswell is-staff   3374 2013-10-27 07:54 share\doc\api\lib\trait.png
-rwxr-xr-x  1 doswell is-staff   8967 2013-10-27 07:54 share\doc\api\lib\trait_to_object_big.png
-rwxr-xr-x  1 doswell is-staff   1206 2013-10-27 07:54 share\doc\api\lib\typebg.gif

using the replace on the path string still looks to be necessary.