According to java.com they offer now version 8.
I've tested SH3D v4.6 & v5.0beta with java 6,7 and 8.
Empty or new plan are open correctly with jre1.8u45, but the previously created especially large one (>5M or >6M) don't show the menu, plan window, furniture window etc.
The 3D window are showed instantly and correct.
I think You can consider to switch to java v8 wile they don't offer support for older versions.
For me (under debian) is not necessarily a problem but for others.