soft reference memory cache

I am caching some huge objects in a JCS disc cache. The objects are 3-15MB in serialized size and there are a lot of them. The normal setup with a LRUMemoryCache and a IndexedDiskCache works fine, but I would like to store as many objects in ram as possible without risking going out of ram. To get to this goal I have created a SoftReferenceMemoryCache that is based on a ConcurrentHashMap<Serializable, SoftReference<ICacheElement>>

This task is to track the work and discuss this with others. Or perhaps get some feedback that this is not a good idea.