### Question:
DefaultFileSystemManager implements FileSystemManager { @Override public FileObject resolveFile(final String uri) throws FileSystemException { return resolveFile(getBaseFile(), uri); }  void addProvider(final String urlScheme, final FileProvider provider); void addProvider(final String[] urlSchemes, final FileProvider provider); @Override boolean hasProvider(final String scheme); void addExtensionMap(final String extension, final String scheme); void addMimeTypeMap(final String mimeType, final String scheme); void setDefaultProvider(final FileProvider provider); @Override FilesCache getFilesCache(); void setFilesCache(final FilesCache filesCache); void setCacheStrategy(final CacheStrategy fileCacheStrategy); @Override CacheStrategy getCacheStrategy(); @Override Class<?> getFileObjectDecorator(); @Override Constructor<?> getFileObjectDecoratorConst(); void setFileObjectDecorator(final Class<?> fileObjectDecorator); @Override FileContentInfoFactory getFileContentInfoFactory(); void setFileContentInfoFactory(final FileContentInfoFactory fileContentInfoFactory); void setReplicator(final FileReplicator replicator); void setTemporaryFileStore(final TemporaryFileStore tempFileStore); @Override void setLogger(final Log log); FileReplicator getReplicator(); TemporaryFileStore getTemporaryFileStore(); void init(); @Override void close(); void freeUnusedResources(); void setBaseFile(final FileObject baseFile); void setBaseFile(final File baseFile); @Override FileObject getBaseFile(); @Override FileObject resolveFile(final String uri); @Override FileObject resolveFile(final String uri, final FileSystemOptions fileSystemOptions); @Override FileObject resolveFile(final File baseFile, final String uri); @Override FileObject resolveFile(final FileObject baseFile, final String uri); FileObject resolveFile(final FileObject baseFile, final String uri,
            final FileSystemOptions fileSystemOptions); @Override FileName resolveName(final FileName root, final String path); @Override FileName resolveName(final FileName base, final String name, final NameScope scope); @Override FileName resolveURI(final String uri); @Override FileObject toFileObject(final File file); @Override FileObject createFileSystem(final String scheme, final FileObject file); @Override FileObject createFileSystem(final FileObject file); @Override boolean canCreateFileSystem(final FileObject file); @Override FileObject createVirtualFileSystem(final FileObject rootFile); @Override FileObject createVirtualFileSystem(final String rootUri); @Override URLStreamHandlerFactory getURLStreamHandlerFactory(); @Override void closeFileSystem(final FileSystem fileSystem); void _closeFileSystem(final FileSystem fileSystem); @Override String[] getSchemes(); @Override Collection<Capability> getProviderCapabilities(final String scheme); @Override FileSystemConfigBuilder getFileSystemConfigBuilder(final String scheme); @Override void addOperationProvider(final String scheme, final FileOperationProvider operationProvider); @Override void addOperationProvider(final String[] schemes, final FileOperationProvider operationProvider); @Override FileOperationProvider[] getOperationProviders(final String scheme); @Override FileObject resolveFile(final URI uri); @Override FileObject resolveFile(final URL url);  }### Answer:
@Test public void test_close() throws FileSystemException { try (FileSystemManager fileSystemManager = new DefaultFileSystemManager()) { VFS.setManager(fileSystemManager); VFS.setManager(null); } Assert.assertNotNull(VFS.getManager()); Assert.assertFalse(VFS.getManager().resolveFile(Paths.get("DoesNotExist.not").toUri()).exists()); }