Photos uploading stalls at 95%

10.10.4 has only added a brief glimpse of the "preparing" blue progress bar to Photos preference. iMac continues looping between "Uploading 1615 items" and "Preparing 1371 items" at the end of a library of 41,000 photos. I've signed off iCloud twice. First time it appeared that the remaining items list was shortened. The second time it appeared to go through all 41,000 photos but at a high rate. Just read a comment that Java 8 fixed a similar case but I really don't think I need Java. So, one question is do I need Java? Another question, should I rename the current Photos library to save it and let Photos create a new one from iPhotos?