working on JDK-8158184, I noticed that "jdk.test.lib.FileInstaller A A" leads to NPE:

java.lang.NullPointerException
        at jdk.test.lib.FileInstaller.main(FileInstaller.java:55)
        at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(java.base@9-internal/Native Method)
        at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(java.base@9-internal/NativeMethodAccessorImpl.java:62)
        at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(java.base@9-internal/DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(java.base@9-internal/Method.java:531)
        at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:110)
        at java.lang.Thread.run(java.base@9-internal/Thread.java:843)


this happens because Path dstDir = dst.getParent() will be null, if dst is in the current directory.