glusterfs-java-filesystem-example exception throws

[lixp]

while run Example.java,exception message is:
Exception in thread "main" java.io.IOException: Unable to close filesystem: dr
at com.peircean.glusterfs.GlusterFileSystem.close(GlusterFileSystem.java:44)
at com.peircean.glusterfs.example.Example.main(Example.java:167)
dr is the gluster server's volume name.the close method is necessary？thx