### Question:
S3FileSystem extends FileSystem implements Comparable<S3FileSystem> { @Override public UserPrincipalLookupService getUserPrincipalLookupService() { throw new UnsupportedOperationException(); } S3FileSystem(S3FileSystemProvider provider, String key, AmazonS3 client, String endpoint); @Override S3FileSystemProvider provider(); String getKey(); @Override void close(); @Override boolean isOpen(); @Override boolean isReadOnly(); @Override String getSeparator(); @Override Iterable<Path> getRootDirectories(); @Override Iterable<FileStore> getFileStores(); @Override Set<String> supportedFileAttributeViews(); @Override S3Path getPath(String first, String... more); @Override PathMatcher getPathMatcher(String syntaxAndPattern); @Override UserPrincipalLookupService getUserPrincipalLookupService(); @Override WatchService newWatchService(); AmazonS3 getClient(); String getEndpoint(); String[] key2Parts(String keyParts); @Override int hashCode(); @Override boolean equals(Object obj); @Override int compareTo(S3FileSystem o); int getCache();  }### Answer:
@Test(expected = UnsupportedOperationException.class) public void getUserPrincipalLookupServiceThrowException() { fs.getUserPrincipalLookupService(); }