public abstract class FileStore extends Object
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
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionabstract Object
getAttribute(String attribute)
Reads the value of a file store attribute.long
Returns the number of bytes per block in this file store.abstract <V extends FileStoreAttributeView>
VgetFileStoreAttributeView(Class<V> type)
Returns aFileStoreAttributeView
of the given type.abstract long
Returns the size, in bytes, of the file store.abstract long
Returns the number of unallocated bytes in the file store.abstract long
Returns the number of bytes available to this Java virtual machine on the file store.abstract boolean
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.
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Constructor Details
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FileStore
protected FileStore()Initializes a new instance of this class.
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Method Details
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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
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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
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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 anIOException
to be thrown.- Returns:
true
if, and only if, this file store is read-only
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getTotalSpace
Returns the size, in bytes, of the file store. If the total number of bytes in the file store is greater thanLong.MAX_VALUE
, thenLong.MAX_VALUE
will be returned.- Returns:
- the size of the file store, in bytes
- Throws:
IOException
- if an I/O error occurs
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getUsableSpace
Returns the number of bytes available to this Java virtual machine on the file store. If the number of bytes available is greater thanLong.MAX_VALUE
, thenLong.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
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getUnallocatedSpace
Returns the number of unallocated bytes in the file store. If the number of unallocated bytes is greater thanLong.MAX_VALUE
, thenLong.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
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getBlockSize
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 occursUnsupportedOperationException
- if the operation is not supported- Since:
- 10
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supportsFileAttributeView
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 returntrue
. 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
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supportsFileAttributeView
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 returntrue
. 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
- thename
of file attribute view- Returns:
true
if, and only if, the file attribute view is supported
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getFileStoreAttributeView
Returns aFileStoreAttributeView
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
- TheFileStoreAttributeView
type- Parameters:
type
- theClass
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
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getAttribute
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 aAttributeView
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 attributeIOException
- if an I/O error occurs
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