After JDK-8218265 the test java/util/Base64/TestEncodingDecodingLength.java fails on machines with 8GB of memory. The test checks that the machine has at least 8GB of memory but then starts a VM with -Xmx8GB heap setting. This will need more than 8GB of memory in total and will fail on machines with only 8GB and no swap configured.
I suggest to increase the check to 10 GB memory to be on the safe side.