Module java.base

Package java.nio.file

Class FileStore

java.lang.Object

java.nio.file.FileStore

public abstract class FileStore
extends Object

Storage for files. A FileStore represents a storage pool, device, partition, volume, concrete file system or other implementation specific means of file storage. The FileStore for where a file is stored is obtained by invoking the getFileStore method, or all file stores can be enumerated by invoking the getFileStores method.

In addition to the methods defined by this class, a file store may support one or more FileStoreAttributeView classes that provide a read-only or updatable view of a set of file store attributes.

Since:

1.7

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
abstract Object	getAttribute(String attribute)	Reads the value of a file store attribute.
long	getBlockSize()	Returns the number of bytes per block in this file store.
abstract <V extends FileStoreAttributeView> V	getFileStoreAttributeView(Class<V> type)	Returns a FileStoreAttributeView of the given type.
abstract long	getTotalSpace()	Returns the size, in bytes, of the file store.
abstract long	getUnallocatedSpace()	Returns the number of unallocated bytes in the file store.
abstract long	getUsableSpace()	Returns the number of bytes available to this Java virtual machine on the file store.
abstract boolean	isReadOnly()	Tells whether this file store is read-only.
abstract String	name()	Returns the name of this file store.
abstract boolean	supportsFileAttributeView(Class<? extends FileAttributeView> type)	Tells whether or not this file store supports the file attributes identified by the given file attribute view.
abstract boolean	supportsFileAttributeView(String name)	Tells whether or not this file store supports the file attributes identified by the given file attribute view.
abstract String	type()	Returns the type of this file store.

Methods declared in class java.lang.Object

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

Constructor Details

FileStore

protected FileStore()

Initializes a new instance of this class.

Method Details

name

public abstract String name()

Returns the name of this file store. The format of the name is highly implementation specific. It will typically be the name of the storage pool or volume.

The string returned by this method may differ from the string returned by the toString method.

Returns:

the name of this file store

type

public abstract String type()

Returns the type of this file store. The format of the string returned by this method is highly implementation specific. It may indicate, for example, the format used or if the file store is local or remote.

Returns:

a string representing the type of this file store

isReadOnly

public abstract boolean isReadOnly()

Tells whether this file store is read-only. A file store is read-only if it does not support write operations or other changes to files. Any attempt to create a file, open an existing file for writing etc. causes an IOException to be thrown.

Returns:

true if, and only if, this file store is read-only

getTotalSpace

public abstract long getTotalSpace()
                            throws IOException

Returns the size, in bytes, of the file store. If the total number of bytes in the file store is greater than Long.MAX_VALUE, then Long.MAX_VALUE will be returned.

Returns:

the size of the file store, in bytes

Throws:

IOException - if an I/O error occurs

getUsableSpace

public abstract long getUsableSpace()
                             throws IOException

Returns the number of bytes available to this Java virtual machine on the file store. If the number of bytes available is greater than Long.MAX_VALUE, then Long.MAX_VALUE will be returned.

The returned number of available bytes is a hint, but not a guarantee, that it is possible to use most or any of these bytes. The number of usable bytes is most likely to be accurate immediately after the space attributes are obtained. It is likely to be made inaccurate by any external I/O operations including those made on the system outside of this Java virtual machine.

Returns:

the number of bytes available

Throws:

IOException - if an I/O error occurs

getUnallocatedSpace

public abstract long getUnallocatedSpace()
                                  throws IOException

Returns the number of unallocated bytes in the file store. If the number of unallocated bytes is greater than Long.MAX_VALUE, then Long.MAX_VALUE will be returned.

The returned number of unallocated bytes is a hint, but not a guarantee, that it is possible to use most or any of these bytes. The number of unallocated bytes is most likely to be accurate immediately after the space attributes are obtained. It is likely to be made inaccurate by any external I/O operations including those made on the system outside of this virtual machine.

Returns:

the number of unallocated bytes

Throws:

IOException - if an I/O error occurs

getBlockSize

public long getBlockSize()
                  throws IOException

Returns the number of bytes per block in this file store.

File storage is typically organized into discrete sequences of bytes called blocks. A block is the smallest storage unit of a file store. Every read and write operation is performed on a multiple of blocks.

Implementation Requirements:

The implementation in this class throws UnsupportedOperationException.

Returns:

a positive value representing the block size of this file store, in bytes

Throws:

IOException - if an I/O error occurs

UnsupportedOperationException - if the operation is not supported

Since:

10

supportsFileAttributeView

public abstract boolean supportsFileAttributeView(Class<? extends FileAttributeView> type)

Tells whether or not this file store supports the file attributes identified by the given file attribute view.

Invoking this method to test if the file store supports BasicFileAttributeView will always return true. In the case of the default provider, this method cannot guarantee to give the correct result when the file store is not a local storage device. The reasons for this are implementation specific and therefore unspecified.

Parameters:

type - the file attribute view type

Returns:

true if, and only if, the file attribute view is supported

supportsFileAttributeView

public abstract boolean supportsFileAttributeView(String name)

Tells whether or not this file store supports the file attributes identified by the given file attribute view.

Invoking this method to test if the file store supports BasicFileAttributeView, identified by the name "basic" will always return true. In the case of the default provider, this method cannot guarantee to give the correct result when the file store is not a local storage device. The reasons for this are implementation specific and therefore unspecified.

Parameters:

name - the name of file attribute view

Returns:

true if, and only if, the file attribute view is supported

getFileStoreAttributeView

public abstract <V extends FileStoreAttributeView>
V getFileStoreAttributeView(Class<V> type)

Returns a FileStoreAttributeView of the given type.

This method is intended to be used where the file store attribute view defines type-safe methods to read or update the file store attributes. The type parameter is the type of the attribute view required and the method returns an instance of that type if supported.

Type Parameters:

V - The FileStoreAttributeView type

Parameters:

type - the Class object corresponding to the attribute view

Returns:

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

getAttribute

public abstract Object getAttribute(String attribute)
                             throws IOException

Reads the value of a file store attribute.

The attribute parameter identifies the attribute to be read and takes the form:

view-name:attribute-name

where the character ':' stands for itself.

view-name is the name of a AttributeView that identifies a set of file attributes. attribute-name is the name of the attribute.

Usage Example: Suppose we want to know if ZFS compression is enabled (assuming the "zfs" view is supported):

    boolean compression = (Boolean)fs.getAttribute("zfs:compression");

Parameters:

attribute - the attribute to read

Returns:

the attribute value; null may be valid for some attributes

Throws:

UnsupportedOperationException - if the attribute view is not available or it does not support reading the attribute

IOException - if an I/O error occurs