Class FileSystem
- All Implemented Interfaces:
Closeable
,AutoCloseable
The default file system, obtained by invoking the FileSystems.getDefault
method, provides access to the file system that is
accessible to the Java virtual machine. The FileSystems
class defines
methods to create file systems that provide access to other types of (custom)
file systems.
A file system is the factory for several types of objects:
The
getPath
method converts a system dependent path string, returning aPath
object that may be used to locate and access a file.The
getPathMatcher
method is used to create aPathMatcher
that performs match operations on paths.The
getFileStores
method returns an iterator over the underlyingfile-stores
.The
getUserPrincipalLookupService
method returns theUserPrincipalLookupService
to lookup users or groups by name.The
newWatchService
method creates aWatchService
that may be used to watch objects for changes and events.
File systems vary greatly. In some cases the file system is a single
hierarchy of files with one top-level root directory. In other cases it may
have several distinct file hierarchies, each with its own top-level root
directory. The getRootDirectories
method may be
used to iterate over the root directories in the file system. A file system
is typically composed of one or more underlying file-stores
that provide the storage for the files. These file stores can also vary in
the features they support, and the file attributes or meta-data that
they associate with files.
A file system is open upon creation and can be closed by invoking its
close
method. Once closed, any further attempt to access
objects in the file system cause ClosedFileSystemException
to be
thrown. File systems created by the default provider
cannot be closed.
A FileSystem
can provide read-only or read-write access to the
file system. Whether or not a file system provides read-only access is
established when the FileSystem
is created and can be tested by invoking
its isReadOnly
method. Attempts to write to file stores
by means of an object associated with a read-only file system throws ReadOnlyFileSystemException
.
File systems are safe for use by multiple concurrent threads. The close
method may be invoked at any time to close a file system but
whether a file system is asynchronously closeable is provider specific
and therefore unspecified. In other words, if a thread is accessing an
object in a file system, and another thread invokes the close
method
then it may require to block until the first operation is complete. Closing
a file system causes all open channels, watch services, and other closeable
objects associated with the file system to be closed.
- Since:
- 1.7
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionabstract void
close()
Closes this file system.Returns an object to iterate over the underlying file stores.abstract Path
Converts a path string, or a sequence of strings that when joined form a path string, to aPath
.abstract PathMatcher
getPathMatcher
(String syntaxAndPattern) Returns aPathMatcher
that performs match operations on theString
representation ofPath
objects by interpreting a given pattern.Returns an object to iterate over the paths of the root directories.abstract String
Returns the name separator, represented as a string.abstract UserPrincipalLookupService
Returns theUserPrincipalLookupService
for this file system (optional operation).abstract boolean
isOpen()
Tells whether or not this file system is open.abstract boolean
Tells whether or not this file system allows only read-only access to its file stores.abstract WatchService
Constructs a newWatchService
(optional operation).abstract FileSystemProvider
provider()
Returns the provider that created this file system.Returns the set of thenames
of the file attribute views supported by thisFileSystem
.
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Constructor Details
-
FileSystem
protected FileSystem()Initializes a new instance of this class.
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-
Method Details
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provider
Returns the provider that created this file system.- Returns:
- The provider that created this file system.
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close
Closes this file system.After a file system is closed then all subsequent access to the file system, either by methods defined by this class or on objects associated with this file system, throw
ClosedFileSystemException
. If the file system is already closed then invoking this method has no effect.Closing a file system will close all open
channels
,directory-streams
,watch-service
, and other closeable objects associated with this file system. Thedefault
file system cannot be closed.- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Throws:
IOException
- If an I/O error occursUnsupportedOperationException
- Thrown in the case of the default file system
-
isOpen
public abstract boolean isOpen()Tells whether or not this file system is open.File systems created by the default provider are always open.
- Returns:
true
if, and only if, this file system is open
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isReadOnly
public abstract boolean isReadOnly()Tells whether or not this file system allows only read-only access to its file stores.- Returns:
true
if, and only if, this file system provides read-only access
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getSeparator
Returns the name separator, represented as a string.The name separator is used to separate names in a path string. An implementation may support multiple name separators in which case this method returns an implementation specific default name separator. This separator is used when creating path strings by invoking the
toString()
method.In the case of the default provider, this method returns the same separator as
File.separator
.- Returns:
- The name separator
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getRootDirectories
Returns an object to iterate over the paths of the root directories.A file system provides access to a file store that may be composed of a number of distinct file hierarchies, each with its own top-level root directory. Unless denied by the security manager, each element in the returned iterator corresponds to the root directory of a distinct file hierarchy. The order of the elements is not defined. The file hierarchies may change during the lifetime of the Java virtual machine. For example, in some implementations, the insertion of removable media may result in the creation of a new file hierarchy with its own top-level directory. There is no guarantee that a root directory can be accessed.
When a security manager is installed, it is invoked to check access to the each root directory. If denied, the root directory is not returned by the iterator. In the case of the default provider, the
SecurityManager.checkRead(String)
method is invoked to check read access to each root directory. It is system dependent if the permission checks are done when the iterator is obtained or during iteration.- Returns:
- An object to iterate over the root directories
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getFileStores
Returns an object to iterate over the underlying file stores.The elements of the returned iterator are the
FileStores
for this file system. The order of the elements is not defined and the file stores may change during the lifetime of the Java virtual machine. When an I/O error occurs, perhaps because a file store is not accessible, then it is not returned by the iterator.In the case of the default provider, and a security manager is installed, the security manager is invoked to check
RuntimePermission
("getFileStoreAttributes")
. If denied, then no file stores are returned by the iterator. In addition, the security manager'sSecurityManager.checkRead(String)
method is invoked to check read access to the file store's top-most directory. If denied, the file store is not returned by the iterator. It is system dependent if the permission checks are done when the iterator is obtained or during iteration.Usage Example: Suppose we want to print the space usage for all file stores:
for (FileStore store: FileSystems.getDefault().getFileStores()) { long total = store.getTotalSpace() / 1024; long used = (store.getTotalSpace() - store.getUnallocatedSpace()) / 1024; long avail = store.getUsableSpace() / 1024; System.out.format("%-20s %12d %12d %12d%n", store, total, used, avail); }
- Returns:
- An object to iterate over the backing file stores
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supportedFileAttributeViews
Returns the set of thenames
of the file attribute views supported by thisFileSystem
.The
BasicFileAttributeView
is required to be supported and therefore the set contains at least one element, "basic".The
supportsFileAttributeView(String)
method may be used to test if an underlyingFileStore
supports the file attributes identified by a file attribute view.- Returns:
- An unmodifiable set of the names of the supported file attribute views
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getPath
Converts a path string, or a sequence of strings that when joined form a path string, to aPath
. Ifmore
does not specify any elements then the value of thefirst
parameter is the path string to convert. Ifmore
specifies one or more elements then each non-empty string, includingfirst
, is considered to be a sequence of name elements (seePath
) and is joined to form a path string. The details as to how the Strings are joined is provider specific but typically they will be joined using thename-separator
as the separator. For example, if the name separator is "/
" andgetPath("/foo","bar","gus")
is invoked, then the path string"/foo/bar/gus"
is converted to aPath
. APath
representing an empty path is returned iffirst
is the empty string andmore
does not contain any non-empty strings.The parsing and conversion to a path object is inherently implementation dependent. In the simplest case, the path string is rejected, and
InvalidPathException
thrown, if the path string contains characters that cannot be converted to characters that are legal to the file store. For example, on UNIX systems, the NUL (\u0000) character is not allowed to be present in a path. An implementation may choose to reject path strings that contain names that are longer than those allowed by any file store, and where an implementation supports a complex path syntax, it may choose to reject path strings that are badly formed.In the case of the default provider, path strings are parsed based on the definition of paths at the platform or virtual file system level. For example, an operating system may not allow specific characters to be present in a file name, but a specific underlying file store may impose different or additional restrictions on the set of legal characters.
This method throws
InvalidPathException
when the path string cannot be converted to a path. Where possible, and where applicable, the exception is created with anindex
value indicating the first position in thepath
parameter that caused the path string to be rejected.- Parameters:
first
- the path string or initial part of the path stringmore
- additional strings to be joined to form the path string- Returns:
- the resulting
Path
- Throws:
InvalidPathException
- If the path string cannot be converted
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getPathMatcher
Returns aPathMatcher
that performs match operations on theString
representation ofPath
objects by interpreting a given pattern. ThesyntaxAndPattern
parameter identifies the syntax and the pattern and takes the form:
where syntax is the non-empty name of the syntax, pattern is a possibly-empty pattern string, andsyntax:pattern
':'
stands for itself.A
FileSystem
implementation supports the "glob
" and "regex
" syntaxes, and may support others. The value of the syntax component is compared without regard to case.When the syntax is "
glob
" then theString
representation of the path is matched using a limited pattern language that resembles regular expressions but with a simpler syntax. For example:Example Description *.java
Matches a path that represents a file name ending in .java
*.*
Matches file names containing a dot *.{java,class}
Matches file names ending with .java
or.class
foo.?
Matches file names starting with foo.
and a single character extension/home/*/*
Matches /home/gus/data
on UNIX platforms/home/**
Matches /home/gus
and/home/gus/data
on UNIX platformsC:\\*
Matches C:\foo
andC:\bar
on the Windows platform (note that the backslash is escaped; as a string literal in the Java Language the pattern would be"C:\\\\*"
)The following rules are used to interpret glob patterns:
The
*
character matches zero or morecharacters
of aname
component without crossing directory boundaries.The
**
characters matches zero or morecharacters
crossing directory boundaries.The
?
character matches exactly one character of a name component.The backslash character (
\
) is used to escape characters that would otherwise be interpreted as special characters. The expression\\
matches a single backslash and "\{" matches a left brace for example.The
[ ]
characters are a bracket expression that match a single character of a name component out of a set of characters. For example,[abc]
matches"a"
,"b"
, or"c"
. The hyphen (-
) may be used to specify a range so[a-z]
specifies a range that matches from"a"
to"z"
(inclusive). These forms can be mixed so [abce-g] matches"a"
,"b"
,"c"
,"e"
,"f"
or"g"
. If the character after the[
is a!
then it is used for negation so[!a-c]
matches any character except"a"
,"b"
, or"c"
.Within a bracket expression the
*
,?
and\
characters match themselves. The (-
) character matches itself if it is the first character within the brackets, or the first character after the!
if negating.The
{ }
characters are a group of subpatterns, where the group matches if any subpattern in the group matches. The","
character is used to separate the subpatterns. Groups cannot be nested.Leading period
/
dot characters in file name are treated as regular characters in match operations. For example, the"*"
glob pattern matches file name".login"
. TheFiles.isHidden(java.nio.file.Path)
method may be used to test whether a file is considered hidden.All other characters match themselves in an implementation dependent manner. This includes characters representing any
name-separators
.The matching of
root
components is highly implementation-dependent and is not specified.
When the syntax is "
regex
" then the pattern component is a regular expression as defined by thePattern
class.For both the glob and regex syntaxes, the matching details, such as whether the matching is case sensitive, are implementation-dependent and therefore not specified.
- Parameters:
syntaxAndPattern
- The syntax and pattern- Returns:
- A path matcher that may be used to match paths against the pattern
- Throws:
IllegalArgumentException
- If the parameter does not take the form:syntax:pattern
PatternSyntaxException
- If the pattern is invalidUnsupportedOperationException
- If the pattern syntax is not known to the implementation- See Also:
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getUserPrincipalLookupService
Returns theUserPrincipalLookupService
for this file system (optional operation). The resulting lookup service may be used to lookup user or group names.Usage Example: Suppose we want to make "joe" the owner of a file:
UserPrincipalLookupService lookupService = FileSystems.getDefault().getUserPrincipalLookupService(); Files.setOwner(path, lookupService.lookupPrincipalByName("joe"));
- Returns:
- The
UserPrincipalLookupService
for this file system - Throws:
UnsupportedOperationException
- If thisFileSystem
does not does have a lookup service
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newWatchService
Constructs a newWatchService
(optional operation).This method constructs a new watch service that may be used to watch registered objects for changes and events.
- Returns:
- a new watch service
- Throws:
UnsupportedOperationException
- If thisFileSystem
does not support watching file system objects for changes and events. This exception is not thrown byFileSystems
created by the default provider.IOException
- If an I/O error occurs
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