Module java.base

Package java.nio.file.spi

Class FileSystemProvider

java.lang.Object

java.nio.file.spi.FileSystemProvider

public abstract class FileSystemProvider
extends Object

Service-provider class for file systems. The methods defined by the Files class will typically delegate to an instance of this class.

A file system provider is a concrete implementation of this class that implements the abstract methods defined by this class. A provider is identified by a URI scheme. The default provider is identified by the URI scheme "file". It creates the FileSystem that provides access to the file systems accessible to the Java virtual machine. The FileSystems class defines how file system providers are located and loaded. The default provider is typically a system-default provider but may be overridden if the system property java.nio.file.spi.DefaultFileSystemProvider is set. In that case, the provider has a one argument constructor whose formal parameter type is FileSystemProvider. All other providers have a zero argument constructor that initializes the provider.

A provider is a factory for one or more FileSystem instances. Each file system is identified by a URI where the URI's scheme matches the provider's scheme. The default file system, for example, is identified by the URI "file:///". A memory-based file system, for example, may be identified by a URI such as "memory:///?name=logfs". The newFileSystem method may be used to create a file system, and the getFileSystem method may be used to obtain a reference to an existing file system created by the provider. Where a provider is the factory for a single file system then it is provider dependent if the file system is created when the provider is initialized, or later when the newFileSystem method is invoked. In the case of the default provider, the FileSystem is created when the provider is initialized.

All of the methods in this class are safe for use by multiple concurrent threads.

Since:

1.7

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	FileSystemProvider()	Initializes a new instance of this class.

Method Summary

Modifier and Type	Method	Description
abstract void	checkAccess(Path path, AccessMode... modes)	Checks the existence, and optionally the accessibility, of a file.
abstract void	copy(Path source, Path target, CopyOption... options)	Copy a file to a target file.
abstract void	createDirectory(Path dir, FileAttribute<?>... attrs)	Creates a new directory.
void	createLink(Path link, Path existing)	Creates a new link (directory entry) for an existing file.
void	createSymbolicLink(Path link, Path target, FileAttribute<?>... attrs)	Creates a symbolic link to a target.
abstract void	delete(Path path)	Deletes a file.
boolean	deleteIfExists(Path path)	Deletes a file if it exists.
boolean	exists(Path path, LinkOption... options)	Tests whether a file exists.
abstract <V extends FileAttributeView> V	getFileAttributeView(Path path, Class<V> type, LinkOption... options)	Returns a file attribute view of a given type.
abstract FileStore	getFileStore(Path path)	Returns the FileStore representing the file store where a file is located.
abstract FileSystem	getFileSystem(URI uri)	Returns an existing FileSystem created by this provider.
abstract Path	getPath(URI uri)	Return a Path object by converting the given URI.
abstract String	getScheme()	Returns the URI scheme that identifies this provider.
static List<FileSystemProvider>	installedProviders()	Returns a list of the installed file system providers.
abstract boolean	isHidden(Path path)	Tells whether or not a file is considered hidden.
abstract boolean	isSameFile(Path path, Path path2)	Tests if two paths locate the same file.
abstract void	move(Path source, Path target, CopyOption... options)	Move or rename a file to a target file.
AsynchronousFileChannel	newAsynchronousFileChannel(Path path, Set<? extends OpenOption> options, ExecutorService executor, FileAttribute<?>... attrs)	Opens or creates a file for reading and/or writing, returning an asynchronous file channel to access the file.
abstract SeekableByteChannel	newByteChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs)	Opens or creates a file, returning a seekable byte channel to access the file.
abstract DirectoryStream<Path>	newDirectoryStream(Path dir, DirectoryStream.Filter<? super Path> filter)	Opens a directory, returning a DirectoryStream to iterate over the entries in the directory.
FileChannel	newFileChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs)	Opens or creates a file for reading and/or writing, returning a file channel to access the file.
abstract FileSystem	newFileSystem(URI uri, Map<String,?> env)	Constructs a new FileSystem object identified by a URI.
FileSystem	newFileSystem(Path path, Map<String,?> env)	Constructs a new FileSystem to access the contents of a file as a file system.
InputStream	newInputStream(Path path, OpenOption... options)	Opens a file, returning an input stream to read from the file.
OutputStream	newOutputStream(Path path, OpenOption... options)	Opens or creates a file, returning an output stream that may be used to write bytes to the file.
abstract <A extends BasicFileAttributes> A	readAttributes(Path path, Class<A> type, LinkOption... options)	Reads a file's attributes as a bulk operation.
abstract Map<String,Object>	readAttributes(Path path, String attributes, LinkOption... options)	Reads a set of file attributes as a bulk operation.
<A extends BasicFileAttributes> A	readAttributesIfExists(Path path, Class<A> type, LinkOption... options)	Reads a file's attributes as a bulk operation if it exists.
Path	readSymbolicLink(Path link)	Reads the target of a symbolic link.
abstract void	setAttribute(Path path, String attribute, Object value, LinkOption... options)	Sets the value of a file attribute.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

FileSystemProvider

protected FileSystemProvider()

Initializes a new instance of this class.

During construction a provider may safely access files associated with the default provider but care needs to be taken to avoid circular loading of other installed providers. If circular loading of installed providers is detected then an unspecified error is thrown.

Throws:

SecurityException - If a security manager has been installed and it denies RuntimePermission("fileSystemProvider")

Method Details

installedProviders

public static List<FileSystemProvider> installedProviders()

Returns a list of the installed file system providers.

The first invocation of this method causes the default provider to be initialized (if not already initialized) and loads any other installed providers as described by the FileSystems class.

Returns:

An unmodifiable list of the installed file system providers. The list contains at least one element, that is the default file system provider

Throws:

ServiceConfigurationError - When an error occurs while loading a service provider

getScheme

public abstract String getScheme()

Returns the URI scheme that identifies this provider.

Returns:

The URI scheme

newFileSystem

public abstract FileSystem newFileSystem(URI uri,
 Map<String,?> env)
                                  throws IOException

Constructs a new FileSystem object identified by a URI. This method is invoked by the FileSystems.newFileSystem(URI,Map) method to open a new file system identified by a URI.

The uri parameter is an absolute, hierarchical URI, with a scheme equal (without regard to case) to the scheme supported by this provider. The exact form of the URI is highly provider dependent. The env parameter is a map of provider specific properties to configure the file system.

This method throws FileSystemAlreadyExistsException if the file system already exists because it was previously created by an invocation of this method. Once a file system is closed it is provider-dependent if the provider allows a new file system to be created with the same URI as a file system it previously created.

Parameters:

uri - URI reference

env - A map of provider specific properties to configure the file system; may be empty

Returns:

A new file system

Throws:

IllegalArgumentException - If the pre-conditions for the uri parameter aren't met, or the env parameter does not contain properties required by the provider, or a property value is invalid

IOException - An I/O error occurs creating the file system

SecurityException - If a security manager is installed and it denies an unspecified permission required by the file system provider implementation

FileSystemAlreadyExistsException - If the file system has already been created

getFileSystem

public abstract FileSystem getFileSystem(URI uri)

Returns an existing FileSystem created by this provider.

This method returns a reference to a FileSystem that was created by invoking the newFileSystem(URI,Map) method. File systems created the newFileSystem(Path,Map) method are not returned by this method. The file system is identified by its URI. Its exact form is highly provider dependent. In the case of the default provider the URI's path component is "/" and the authority, query and fragment components are undefined (Undefined components are represented by null).

Once a file system created by this provider is closed it is provider-dependent if this method returns a reference to the closed file system or throws FileSystemNotFoundException. If the provider allows a new file system to be created with the same URI as a file system it previously created then this method throws the exception if invoked after the file system is closed (and before a new instance is created by the newFileSystem method).

If a security manager is installed then a provider implementation may require to check a permission before returning a reference to an existing file system. In the case of the default file system, no permission check is required.

Parameters:

uri - URI reference

Returns:

The file system

Throws:

IllegalArgumentException - If the pre-conditions for the uri parameter aren't met

FileSystemNotFoundException - If the file system does not exist

SecurityException - If a security manager is installed and it denies an unspecified permission.

getPath

public abstract Path getPath(URI uri)

Return a Path object by converting the given URI. The resulting Path is associated with a FileSystem that already exists or is constructed automatically.

The exact form of the URI is file system provider dependent. In the case of the default provider, the URI scheme is "file" and the given URI has a non-empty path component, and undefined query, and fragment components. The resulting Path is associated with the default default FileSystem.

If a security manager is installed then a provider implementation may require to check a permission. In the case of the default file system, no permission check is required.

Parameters:

uri - The URI to convert

Returns:

The resulting Path

Throws:

IllegalArgumentException - If the URI scheme does not identify this provider or other preconditions on the uri parameter do not hold

FileSystemNotFoundException - The file system, identified by the URI, does not exist and cannot be created automatically

SecurityException - If a security manager is installed and it denies an unspecified permission.

newFileSystem

public FileSystem newFileSystem(Path path,
 Map<String,?> env)
                         throws IOException

Constructs a new FileSystem to access the contents of a file as a file system.

This method is intended for specialized providers of pseudo file systems where the contents of one or more files is treated as a file system. The env parameter is a map of provider specific properties to configure the file system.

If this provider does not support the creation of such file systems or if the provider does not recognize the file type of the given file then it throws UnsupportedOperationException. The default implementation of this method throws UnsupportedOperationException.

Parameters:

path - The path to the file

env - A map of provider specific properties to configure the file system; may be empty

Returns:

A new file system

Throws:

UnsupportedOperationException - If this provider does not support access to the contents as a file system or it does not recognize the file type of the given file

IllegalArgumentException - If the env parameter does not contain properties required by the provider, or a property value is invalid

IOException - If an I/O error occurs

SecurityException - If a security manager is installed and it denies an unspecified permission.

newInputStream

public InputStream newInputStream(Path path,
 OpenOption... options)
                           throws IOException

Opens a file, returning an input stream to read from the file. This method works in exactly the manner specified by the Files.newInputStream(java.nio.file.Path, java.nio.file.OpenOption...) method.

The default implementation of this method opens a channel to the file as if by invoking the newByteChannel(java.nio.file.Path, java.util.Set<? extends java.nio.file.OpenOption>, java.nio.file.attribute.FileAttribute<?>...) method and constructs a stream that reads bytes from the channel. This method should be overridden where appropriate.

Parameters:

path - the path to the file to open

options - options specifying how the file is opened

Returns:

a new input stream

Throws:

IllegalArgumentException - if an invalid combination of options is specified

UnsupportedOperationException - if an unsupported option is specified

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file.

newOutputStream

public OutputStream newOutputStream(Path path,
 OpenOption... options)
                             throws IOException

Opens or creates a file, returning an output stream that may be used to write bytes to the file. This method works in exactly the manner specified by the Files.newOutputStream(java.nio.file.Path, java.nio.file.OpenOption...) method.

The default implementation of this method opens a channel to the file as if by invoking the newByteChannel(java.nio.file.Path, java.util.Set<? extends java.nio.file.OpenOption>, java.nio.file.attribute.FileAttribute<?>...) method and constructs a stream that writes bytes to the channel. This method should be overridden where appropriate.

Parameters:

path - the path to the file to open or create

options - options specifying how the file is opened

Returns:

a new output stream

Throws:

IllegalArgumentException - if options contains an invalid combination of options

UnsupportedOperationException - if an unsupported option is specified

IOException - if an I/O error occurs

FileAlreadyExistsException - If a file of that name already exists and the CREATE_NEW option is specified (optional specific exception)

SecurityException - In the case of the default provider, and a security manager is installed, the checkWrite method is invoked to check write access to the file. The checkDelete method is invoked to check delete access if the file is opened with the DELETE_ON_CLOSE option.

newFileChannel

public FileChannel newFileChannel(Path path,
 Set<? extends OpenOption> options,
 FileAttribute<?>... attrs)
                           throws IOException

Opens or creates a file for reading and/or writing, returning a file channel to access the file. This method works in exactly the manner specified by the FileChannel.open method. A provider that does not support all the features required to construct a file channel throws UnsupportedOperationException. The default provider is required to support the creation of file channels. When not overridden, the default implementation throws UnsupportedOperationException.

Parameters:

path - the path of the file to open or create

options - options specifying how the file is opened

attrs - an optional list of file attributes to set atomically when creating the file

Returns:

a new file channel

Throws:

IllegalArgumentException - If the set contains an invalid combination of options

UnsupportedOperationException - If this provider that does not support creating file channels, or an unsupported open option or file attribute is specified

FileAlreadyExistsException - If a file of that name already exists and the CREATE_NEW option is specified and the file is being opened for writing (optional specific exception)

IOException - If an I/O error occurs

SecurityException - In the case of the default file system, the SecurityManager.checkRead(String) method is invoked to check read access if the file is opened for reading. The SecurityManager.checkWrite(String) method is invoked to check write access if the file is opened for writing

newAsynchronousFileChannel

public AsynchronousFileChannel newAsynchronousFileChannel(Path path,
 Set<? extends OpenOption> options,
 ExecutorService executor,
 FileAttribute<?>... attrs)
                                                   throws IOException

Opens or creates a file for reading and/or writing, returning an asynchronous file channel to access the file. This method works in exactly the manner specified by the AsynchronousFileChannel.open method. A provider that does not support all the features required to construct an asynchronous file channel throws UnsupportedOperationException. The default provider is required to support the creation of asynchronous file channels. When not overridden, the default implementation of this method throws UnsupportedOperationException.

Parameters:

path - the path of the file to open or create

options - options specifying how the file is opened

executor - the thread pool or null to associate the channel with the default thread pool

attrs - an optional list of file attributes to set atomically when creating the file

Returns:

a new asynchronous file channel

Throws:

IllegalArgumentException - If the set contains an invalid combination of options

UnsupportedOperationException - If this provider that does not support creating asynchronous file channels, or an unsupported open option or file attribute is specified

FileAlreadyExistsException - If a file of that name already exists and the CREATE_NEW option is specified and the file is being opened for writing (optional specific exception)

IOException - If an I/O error occurs

SecurityException - In the case of the default file system, the SecurityManager.checkRead(String) method is invoked to check read access if the file is opened for reading. The SecurityManager.checkWrite(String) method is invoked to check write access if the file is opened for writing

newByteChannel

public abstract SeekableByteChannel newByteChannel(Path path,
 Set<? extends OpenOption> options,
 FileAttribute<?>... attrs)
                                            throws IOException

Opens or creates a file, returning a seekable byte channel to access the file. This method works in exactly the manner specified by the Files.newByteChannel(Path,Set,FileAttribute[]) method.

Parameters:

path - the path to the file to open or create

options - options specifying how the file is opened

attrs - an optional list of file attributes to set atomically when creating the file

Returns:

a new seekable byte channel

Throws:

IllegalArgumentException - if the set contains an invalid combination of options

UnsupportedOperationException - if an unsupported open option is specified or the array contains attributes that cannot be set atomically when creating the file

FileAlreadyExistsException - If a file of that name already exists and the CREATE_NEW option is specified and the file is being opened for writing (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the path if the file is opened for reading. The checkWrite method is invoked to check write access to the path if the file is opened for writing. The checkDelete method is invoked to check delete access if the file is opened with the DELETE_ON_CLOSE option.

newDirectoryStream

public abstract DirectoryStream<Path> newDirectoryStream(Path dir,
 DirectoryStream.Filter<? super Path> filter)
                                                  throws IOException

Opens a directory, returning a DirectoryStream to iterate over the entries in the directory. This method works in exactly the manner specified by the Files.newDirectoryStream(java.nio.file.Path, java.nio.file.DirectoryStream.Filter) method.

Parameters:

dir - the path to the directory

filter - the directory stream filter

Returns:

a new and open DirectoryStream object

Throws:

NotDirectoryException - if the file could not otherwise be opened because it is not a directory (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the directory.

createDirectory

public abstract void createDirectory(Path dir,
 FileAttribute<?>... attrs)
                              throws IOException

Creates a new directory. This method works in exactly the manner specified by the Files.createDirectory(java.nio.file.Path, java.nio.file.attribute.FileAttribute<?>...) method.

Parameters:

dir - the directory to create

attrs - an optional list of file attributes to set atomically when creating the directory

Throws:

UnsupportedOperationException - if the array contains an attribute that cannot be set atomically when creating the directory

FileAlreadyExistsException - if a directory could not otherwise be created because a file of that name already exists (optional specific exception)

IOException - if an I/O error occurs or the parent directory does not exist

SecurityException - In the case of the default provider, and a security manager is installed, the checkWrite method is invoked to check write access to the new directory.

createSymbolicLink

public void createSymbolicLink(Path link,
 Path target,
 FileAttribute<?>... attrs)
                        throws IOException

Creates a symbolic link to a target. This method works in exactly the manner specified by the Files.createSymbolicLink(java.nio.file.Path, java.nio.file.Path, java.nio.file.attribute.FileAttribute<?>...) method.

The default implementation of this method throws UnsupportedOperationException.

Parameters:

link - the path of the symbolic link to create

target - the target of the symbolic link

attrs - the array of attributes to set atomically when creating the symbolic link

Throws:

UnsupportedOperationException - if the implementation does not support symbolic links or the array contains an attribute that cannot be set atomically when creating the symbolic link

FileAlreadyExistsException - if a file with the name already exists (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, it denies LinkPermission("symbolic") or its checkWrite method denies write access to the path of the symbolic link.

createLink

public void createLink(Path link,
 Path existing)
                throws IOException

Creates a new link (directory entry) for an existing file. This method works in exactly the manner specified by the Files.createLink(java.nio.file.Path, java.nio.file.Path) method.

The default implementation of this method throws UnsupportedOperationException.

Parameters:

link - the link (directory entry) to create

existing - a path to an existing file

Throws:

UnsupportedOperationException - if the implementation does not support adding an existing file to a directory

FileAlreadyExistsException - if the entry could not otherwise be created because a file of that name already exists (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, it denies LinkPermission("hard") or its checkWrite method denies write access to either the link or the existing file.

delete

public abstract void delete(Path path)
                     throws IOException

Deletes a file. This method works in exactly the manner specified by the Files.delete(java.nio.file.Path) method.

Parameters:

path - the path to the file to delete

Throws:

NoSuchFileException - if the file does not exist (optional specific exception)

DirectoryNotEmptyException - if the file is a directory and could not otherwise be deleted because the directory is not empty (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the SecurityManager.checkDelete(String) method is invoked to check delete access to the file

deleteIfExists

public boolean deleteIfExists(Path path)
                       throws IOException

Deletes a file if it exists. This method works in exactly the manner specified by the Files.deleteIfExists(java.nio.file.Path) method.

The default implementation of this method simply invokes delete(java.nio.file.Path) ignoring the NoSuchFileException when the file does not exist. It may be overridden where appropriate.

Parameters:

path - the path to the file to delete

Returns:

true if the file was deleted by this method; false if the file could not be deleted because it did not exist

Throws:

DirectoryNotEmptyException - if the file is a directory and could not otherwise be deleted because the directory is not empty (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the SecurityManager.checkDelete(String) method is invoked to check delete access to the file

readSymbolicLink

public Path readSymbolicLink(Path link)
                      throws IOException

Reads the target of a symbolic link. This method works in exactly the manner specified by the Files.readSymbolicLink(java.nio.file.Path) method.

The default implementation of this method throws UnsupportedOperationException.

Parameters:

link - the path to the symbolic link

Returns:

The target of the symbolic link

Throws:

UnsupportedOperationException - if the implementation does not support symbolic links

NotLinkException - if the target could otherwise not be read because the file is not a symbolic link (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, it checks that FilePermission has been granted with the "readlink" action to read the link.

copy

public abstract void copy(Path source,
 Path target,
 CopyOption... options)
                   throws IOException

Copy a file to a target file. This method works in exactly the manner specified by the Files.copy(Path,Path,CopyOption[]) method except that both the source and target paths must be associated with this provider.

Parameters:

source - the path to the file to copy

target - the path to the target file

options - options specifying how the copy should be done

Throws:

UnsupportedOperationException - if the array contains a copy option that is not supported

FileAlreadyExistsException - if the target file exists but cannot be replaced because the REPLACE_EXISTING option is not specified (optional specific exception)

DirectoryNotEmptyException - the REPLACE_EXISTING option is specified but the file cannot be replaced because it is a non-empty directory (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the source file, the checkWrite is invoked to check write access to the target file. If a symbolic link is copied the security manager is invoked to check LinkPermission("symbolic").

move

public abstract void move(Path source,
 Path target,
 CopyOption... options)
                   throws IOException

Move or rename a file to a target file. This method works in exactly the manner specified by the Files.move(java.nio.file.Path, java.nio.file.Path, java.nio.file.CopyOption...) method except that both the source and target paths must be associated with this provider.

Parameters:

source - the path to the file to move

target - the path to the target file

options - options specifying how the move should be done

Throws:

UnsupportedOperationException - if the array contains a copy option that is not supported

FileAlreadyExistsException - if the target file exists but cannot be replaced because the REPLACE_EXISTING option is not specified (optional specific exception)

DirectoryNotEmptyException - the REPLACE_EXISTING option is specified but the file cannot be replaced because it is a non-empty directory (optional specific exception)

AtomicMoveNotSupportedException - if the options array contains the ATOMIC_MOVE option but the file cannot be moved as an atomic file system operation.

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkWrite method is invoked to check write access to both the source and target file.

isSameFile

public abstract boolean isSameFile(Path path,
 Path path2)
                            throws IOException

Tests if two paths locate the same file. This method works in exactly the manner specified by the Files.isSameFile(java.nio.file.Path, java.nio.file.Path) method.

Parameters:

path - one path to the file

path2 - the other path

Returns:

true if, and only if, the two paths locate the same file

Throws:

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to both files.

isHidden

public abstract boolean isHidden(Path path)
                          throws IOException

Tells whether or not a file is considered hidden. This method works in exactly the manner specified by the Files.isHidden(java.nio.file.Path) method.

This method is invoked by the isHidden method.

Parameters:

path - the path to the file to test

Returns:

true if the file is considered hidden

Throws:

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file.

getFileStore

public abstract FileStore getFileStore(Path path)
                                throws IOException

Returns the FileStore representing the file store where a file is located. This method works in exactly the manner specified by the Files.getFileStore(java.nio.file.Path) method.

Parameters:

path - the path to the file

Returns:

the file store where the file is stored

Throws:

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file, and in addition it checks RuntimePermission("getFileStoreAttributes")

checkAccess

public abstract void checkAccess(Path path,
 AccessMode... modes)
                          throws IOException

Checks the existence, and optionally the accessibility, of a file.

This method may be used by the isReadable, isWritable and isExecutable methods to check the accessibility of a file.

This method checks the existence of a file and that this Java virtual machine has appropriate privileges that would allow it access the file according to all of access modes specified in the modes parameter as follows:

Access Modes

Value	Description
READ	Checks that the file exists and that the Java virtual machine has permission to read the file.
WRITE	Checks that the file exists and that the Java virtual machine has permission to write to the file,
EXECUTE	Checks that the file exists and that the Java virtual machine has permission to execute the file. The semantics may differ when checking access to a directory. For example, on UNIX systems, checking for EXECUTE access checks that the Java virtual machine has permission to search the directory in order to access file or subdirectories.

If the modes parameter is of length zero, then the existence of the file is checked.

This method follows symbolic links if the file referenced by this object is a symbolic link. Depending on the implementation, this method may require to read file permissions, access control lists, or other file attributes in order to check the effective access to the file. To determine the effective access to a file may require access to several attributes and so in some implementations this method may not be atomic with respect to other file system operations.

Parameters:

path - the path to the file to check

modes - The access modes to check; may have zero elements

Throws:

UnsupportedOperationException - an implementation is required to support checking for READ, WRITE, and EXECUTE access. This exception is specified to allow for the Access enum to be extended in future releases.

NoSuchFileException - if a file does not exist (optional specific exception)

AccessDeniedException - the requested access would be denied or the access cannot be determined because the Java virtual machine has insufficient privileges or other reasons. (optional specific exception)

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, the checkRead is invoked when checking read access to the file or only the existence of the file, the checkWrite is invoked when checking write access to the file, and checkExec is invoked when checking execute access.

getFileAttributeView

public abstract <V extends FileAttributeView> V getFileAttributeView(Path path,
 Class<V> type,
 LinkOption... options)

Returns a file attribute view of a given type. This method works in exactly the manner specified by the Files.getFileAttributeView(java.nio.file.Path, java.lang.Class<V>, java.nio.file.LinkOption...) method.

Type Parameters:

V - The FileAttributeView type

Parameters:

path - the path to the file

type - the Class object corresponding to the file attribute view

options - options indicating how symbolic links are handled

Returns:

a file attribute view of the specified type, or null if the attribute view type is not available

readAttributes

public abstract <A extends BasicFileAttributes> A readAttributes(Path path,
 Class<A> type,
 LinkOption... options)
                                                          throws IOException

Reads a file's attributes as a bulk operation. This method works in exactly the manner specified by the Files.readAttributes(Path,Class,LinkOption[]) method.

Type Parameters:

A - The BasicFileAttributes type

Parameters:

path - the path to the file

type - the Class of the file attributes required to read

options - options indicating how symbolic links are handled

Returns:

the file attributes

Throws:

UnsupportedOperationException - if an attributes of the given type are not supported

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, a security manager is installed, its checkRead method is invoked to check read access to the file

readAttributes

public abstract Map<String,Object> readAttributes(Path path,
 String attributes,
 LinkOption... options)
                                           throws IOException

Reads a set of file attributes as a bulk operation. This method works in exactly the manner specified by the Files.readAttributes(Path,String,LinkOption[]) method.

Parameters:

path - the path to the file

attributes - the attributes to read

options - options indicating how symbolic links are handled

Returns:

a map of the attributes returned; may be empty. The map's keys are the attribute names, its values are the attribute values

Throws:

UnsupportedOperationException - if the attribute view is not available

IllegalArgumentException - if no attributes are specified or an unrecognized attributes is specified

IOException - If an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, its checkRead method denies read access to the file. If this method is invoked to read security sensitive attributes then the security manager may be invoked to check for additional permissions.

setAttribute

public abstract void setAttribute(Path path,
 String attribute,
 Object value,
 LinkOption... options)
                           throws IOException

Sets the value of a file attribute. This method works in exactly the manner specified by the Files.setAttribute(java.nio.file.Path, java.lang.String, java.lang.Object, java.nio.file.LinkOption...) method.

Parameters:

path - the path to the file

attribute - the attribute to set

value - the attribute value

options - options indicating how symbolic links are handled

Throws:

UnsupportedOperationException - if the attribute view is not available

IllegalArgumentException - if the attribute name is not specified, or is not recognized, or the attribute value is of the correct type but has an inappropriate value

ClassCastException - If the attribute value is not of the expected type or is a collection containing elements that are not of the expected type

IOException - If an I/O error occurs

SecurityException - In the case of the default provider, and a security manager is installed, its checkWrite method denies write access to the file. If this method is invoked to set security sensitive attributes then the security manager may be invoked to check for additional permissions.

exists

public boolean exists(Path path,
 LinkOption... options)

Tests whether a file exists. This method works in exactly the manner specified by the Files.exists(Path, LinkOption...) method.

Implementation Requirements:

The default implementation of this method invokes the checkAccess(Path, AccessMode...) method when symbolic links are followed. If the option NOFOLLOW_LINKS is present then symbolic links are not followed and the method readAttributes(Path, Class, LinkOption...) is called to determine whether a file exists.

Parameters:

path - the path to the file to test

options - options indicating how symbolic links are handled

Returns:

true if the file exists; false if the file does not exist or its existence cannot be determined.

Throws:

SecurityException - In the case of the default provider, the SecurityManager.checkRead(String) is invoked to check read access to the file.

Since:

20

readAttributesIfExists

public <A extends BasicFileAttributes> A readAttributesIfExists(Path path,
 Class<A> type,
 LinkOption... options)
                                                         throws IOException

Reads a file's attributes as a bulk operation if it exists.

The type parameter is the type of the attributes required and this method returns an instance of that type if supported. All implementations support a basic set of file attributes and so invoking this method with a type parameter of BasicFileAttributes.class will not throw UnsupportedOperationException.

The options array may be used to indicate how symbolic links are handled for the case that the file is a symbolic link. By default, symbolic links are followed and the file attribute of the final target of the link is read. If the option NOFOLLOW_LINKS is present then symbolic links are not followed.

It is implementation specific if all file attributes are read as an atomic operation with respect to other file system operations.

Implementation Requirements:

The default implementation of this method invokes the readAttributes(Path, Class, LinkOption...) method to read the file's attributes.

Type Parameters:

A - The BasicFileAttributes type

Parameters:

path - the path to the file

type - the Class of the file attributes required to read

options - options indicating how symbolic links are handled

Returns:

the file attributes or null if the file does not exist

Throws:

UnsupportedOperationException - if an attributes of the given type are not supported

IOException - if an I/O error occurs

SecurityException - In the case of the default provider, a security manager is installed, its checkRead method is invoked to check read access to the file. If this method is invoked to read security sensitive attributes then the security manager may be invoked to check for additional permissions.

Since:

20