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	/*
	* Copyright (c) 2007, 2020, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.nio.file;

	import java.nio.file.attribute.*;
	import java.io.IOException;

	/**
	* Storage for files. A {@code FileStore} represents a storage pool, device,
	* partition, volume, concrete file system or other implementation specific means
	* of file storage. The {@code FileStore} for where a file is stored is obtained
	* by invoking the {@link Files#getFileStore getFileStore} method, or all file
	* stores can be enumerated by invoking the {@link FileSystem#getFileStores
	* getFileStores} method.
	*
	* <p> In addition to the methods defined by this class, a file store may support
	* one or more {@link FileStoreAttributeView FileStoreAttributeView} classes
	* that provide a read-only or updatable view of a set of file store attributes.
	*
	* @since 1.7
	*/

	public abstract class FileStore {

	/**
	* Initializes a new instance of this class.
	*/
	protected FileStore() {
	}

	/**
	* 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.
	*
	* <p> The string returned by this method may differ from the string
	* returned by the {@link Object#toString() toString} method.
	*
	* @return the name of this file store
	*/
	public abstract String name();

	/**
	* Returns the <em>type</em> 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.
	*
	* @return a string representing the type of this file store
	*/
	public abstract String type();

	/**
	* 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 {@code IOException} to be thrown.
	*
	* @return {@code true} if, and only if, this file store is read-only
	*/
	public abstract boolean isReadOnly();

	/**
	* Returns the size, in bytes, of the file store. If the total number of
	* bytes in the file store is greater than {@link Long#MAX_VALUE}, then
	* {@code Long.MAX_VALUE} will be returned.
	*
	* @return the size of the file store, in bytes
	*
	* @throws IOException
	* if an I/O error occurs
	*/
	public abstract long getTotalSpace() 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
	* {@link Long#MAX_VALUE}, then {@code Long.MAX_VALUE} will be returned.
	*
	* <p> 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.
	*
	* @return the number of bytes available
	*
	* @throws IOException
	* if an I/O error occurs
	*/
	public abstract long getUsableSpace() throws IOException;

	/**
	* Returns the number of unallocated bytes in the file store.
	* If the number of unallocated bytes is greater than
	* {@link Long#MAX_VALUE}, then {@code Long.MAX_VALUE} will be returned.
	*
	* <p> 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.
	*
	* @return the number of unallocated bytes
	*
	* @throws IOException
	* if an I/O error occurs
	*/
	public abstract long getUnallocatedSpace() throws IOException;

	/**
	* Returns the number of bytes per block in this file store.
	*
	* <p> File storage is typically organized into discrete sequences of bytes
	* called <i>blocks</i>. A block is the smallest storage unit of a file store.
	* Every read and write operation is performed on a multiple of blocks.
	*
	* @implSpec The implementation in this class throws
	* {@code UnsupportedOperationException}.
	*
	* @return a positive value representing the block size of this file store,
	* in bytes
	*
	* @throws IOException
	* if an I/O error occurs
	*
	* @throws UnsupportedOperationException
	* if the operation is not supported
	*
	* @since 10
	*/
	public long getBlockSize() throws IOException {
	throw new UnsupportedOperationException();
	}

	/**
	* Tells whether or not this file store supports the file attributes
	* identified by the given file attribute view.
	*
	* <p> Invoking this method to test if the file store supports {@link
	* BasicFileAttributeView} will always return {@code 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.
	*
	* @param type
	* the file attribute view type
	*
	* @return {@code true} if, and only if, the file attribute view is
	* supported
	*/
	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.
	*
	* <p> Invoking this method to test if the file store supports {@link
	* BasicFileAttributeView}, identified by the name "{@code basic}" will
	* always return {@code 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.
	*
	* @param name
	* the {@link FileAttributeView#name name} of file attribute view
	*
	* @return {@code true} if, and only if, the file attribute view is
	* supported
	*/
	public abstract boolean supportsFileAttributeView(String name);

	/**
	* Returns a {@code FileStoreAttributeView} of the given type.
	*
	* <p> 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 {@code type} parameter is the type of the attribute view required and
	* the method returns an instance of that type if supported.
	*
	* @param <V>
	* The {@code FileStoreAttributeView} type
	* @param type
	* the {@code Class} object corresponding to the attribute view
	*
	* @return a file store attribute view of the specified type or
	* {@code null} if the attribute view is not available
	*/
	public abstract <V extends FileStoreAttributeView> V
	getFileStoreAttributeView(Class<V> type);

	/**
	* Reads the value of a file store attribute.
	*
	* <p> The {@code attribute} parameter identifies the attribute to be read
	* and takes the form:
	* <blockquote>
	* <i>view-name</i><b>:</b><i>attribute-name</i>
	* </blockquote>
	* where the character {@code ':'} stands for itself.
	*
	* <p> <i>view-name</i> is the {@link FileStoreAttributeView#name name} of
	* a {@link FileStore AttributeView} that identifies a set of file attributes.
	* <i>attribute-name</i> is the name of the attribute.
	*
	* <p> <b>Usage Example:</b>
	* Suppose we want to know if ZFS compression is enabled (assuming the "zfs"
	* view is supported):
	* <pre>
	* boolean compression = (Boolean)fs.getAttribute("zfs:compression");
	* </pre>
	*
	* @param attribute
	* the attribute to read
	*
	* @return the attribute value; {@code null} may be valid for some
	* attributes
	*
	* @throws UnsupportedOperationException
	* if the attribute view is not available or it does not support
	* reading the attribute
	* @throws IOException
	* if an I/O error occurs
	*/
	public abstract Object getAttribute(String attribute) throws IOException;
	}

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