Regarding JCS

i write code like this:

JCS cache.......
in putObject() method:
cache.put(cacheKey,cacheObject)
cache.get(cacheKey) this is returning cache object.

but in getObject() method:
cache.get(cacheKey) this is returning null

can anyone please tell me the reason.

and please send eg. cache.ccf file i'm using disk cache.

Thank You.
CTS.