public abstract FileSystemProvider provider()

public abstract void close()
                    throws IOException

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. The default file system cannot be closed.

public abstract boolean isOpen()

Tells whether or not this file system is open.

File systems created by the default provider are always open.

public abstract boolean isReadOnly()

public abstract String 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.

public abstract Iterable<Path> 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.

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.

public abstract Iterable<FileStore> 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's SecurityManager.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);
     }

public abstract Set<String> supportedFileAttributeViews()

Returns the set of the names of the file attribute views supported by this FileSystem.

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 underlying FileStore supports the file attributes identified by a file attribute view.

public abstract Path getPath​(String first,
                             String... more)

Converts a path string, or a sequence of strings that when joined form a path string, to a Path. If more does not specify any elements then the value of the first parameter is the path string to convert. If more specifies one or more elements then each non-empty string, including first, is considered to be a sequence of name elements (see Path) 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 the name-separator as the separator. For example, if the name separator is "/" and getPath("/foo","bar","gus") is invoked, then the path string "/foo/bar/gus" is converted to a Path. A Path representing an empty path is returned if first is the empty string and more 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 an index value indicating the first position in the path parameter that caused the path string to be rejected.

public abstract PathMatcher getPathMatcher​(String syntaxAndPattern)

Returns a PathMatcher that performs match operations on the String representation of Path objects by interpreting a given pattern. The syntaxAndPattern parameter identifies the syntax and the pattern and takes the form:

syntax:pattern

where ':' 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 the String representation of the path is matched using a limited pattern language that resembles regular expressions but with a simpler syntax. For example:

Pattern Language

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 platforms
C:\\*	Matches C:\foo and C:\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 more characters of a name component without crossing directory boundaries.

• The ** characters matches zero or more characters 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". The Files.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 the Pattern 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.

public abstract UserPrincipalLookupService getUserPrincipalLookupService()

Returns the UserPrincipalLookupService 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"));

public abstract WatchService newWatchService()
                                      throws IOException

Constructs a new WatchService (optional operation).

This method constructs a new watch service that may be used to watch registered objects for changes and events.