The jtreg test java/awt/font/DefaultFontTest/DefaultFontTest.java fails on one of our RedHat 7.1 machines with :

java.lang.NullPointerException: Cannot invoke "String.toLowerCase(java.util.Locale)" because "name" is null
at java.desktop/sun.font.SunFontManager.findFont2D(SunFontManager.java:1891)
at java.desktop/sun.font.SunFontManager.getDefaultPhysicalFont(SunFontManager.java:1036)
at DefaultFontTest.main(DefaultFontTest.java:57)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.base/java.lang.Thread.run(Thread.java:832)

Looks like name.toLowerCase(Locale.ENGLISH); is called on a name null, this should be checked.