247 lines
9.5 KiB
Java
247 lines
9.5 KiB
Java
/*
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* Copyright (c) 2007, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.nio.file;
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import java.nio.file.attribute.*;
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import java.io.IOException;
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/**
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* Storage for files. A {@code FileStore} represents a storage pool, device,
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* partition, volume, concrete file system or other implementation specific means
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* of file storage. The {@code FileStore} for where a file is stored is obtained
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* by invoking the {@link Files#getFileStore getFileStore} method, or all file
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* stores can be enumerated by invoking the {@link FileSystem#getFileStores
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* getFileStores} method.
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*
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* <p> In addition to the methods defined by this class, a file store may support
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* one or more {@link FileStoreAttributeView FileStoreAttributeView} classes
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* that provide a read-only or updatable view of a set of file store attributes.
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*
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* @since 1.7
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*/
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public abstract class FileStore {
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/**
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* Initializes a new instance of this class.
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*/
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protected FileStore() {
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}
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/**
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* Returns the name of this file store. The format of the name is highly
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* implementation specific. It will typically be the name of the storage
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* pool or volume.
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*
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* <p> The string returned by this method may differ from the string
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* returned by the {@link Object#toString() toString} method.
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*
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* @return the name of this file store
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*/
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public abstract String name();
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/**
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* Returns the <em>type</em> of this file store. The format of the string
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* returned by this method is highly implementation specific. It may
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* indicate, for example, the format used or if the file store is local
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* or remote.
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*
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* @return a string representing the type of this file store
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*/
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public abstract String type();
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/**
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* Tells whether this file store is read-only. A file store is read-only if
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* it does not support write operations or other changes to files. Any
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* attempt to create a file, open an existing file for writing etc. causes
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* an {@code IOException} to be thrown.
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*
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* @return {@code true} if, and only if, this file store is read-only
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*/
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public abstract boolean isReadOnly();
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/**
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* Returns the size, in bytes, of the file store.
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*
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* @return the size of the file store, in bytes
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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public abstract long getTotalSpace() throws IOException;
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/**
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* Returns the number of bytes available to this Java virtual machine on the
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* file store.
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*
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* <p> The returned number of available bytes is a hint, but not a
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* guarantee, that it is possible to use most or any of these bytes. The
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* number of usable bytes is most likely to be accurate immediately
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* after the space attributes are obtained. It is likely to be made inaccurate
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* by any external I/O operations including those made on the system outside
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* of this Java virtual machine.
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*
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* @return the number of bytes available
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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public abstract long getUsableSpace() throws IOException;
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/**
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* Returns the number of bytes per block in this file store.
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*
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* <p> File storage is typically organized into discrete sequences of bytes
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* called <i>blocks</i>. A block is the smallest storage unit of a file store.
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* Every read and write operation is performed on a multiple of blocks.
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*
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* @implSpec The implementation in this class throws an
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* {@code UnsupportedOperationException}.
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*
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* @return a positive value representing the block size of this file store,
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* in bytes
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*
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* @throws IOException
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* if an I/O error occurs
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*
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* @throws UnsupportedOperationException
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* if the operation is not supported
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*
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* @since 10
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*/
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public long getBlockSize() throws IOException {
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throw new UnsupportedOperationException();
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}
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/**
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* Returns the number of unallocated bytes in the file store.
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*
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* <p> The returned number of unallocated bytes is a hint, but not a
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* guarantee, that it is possible to use most or any of these bytes. The
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* number of unallocated bytes is most likely to be accurate immediately
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* after the space attributes are obtained. It is likely to be
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* made inaccurate by any external I/O operations including those made on
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* the system outside of this virtual machine.
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*
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* @return the number of unallocated bytes
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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public abstract long getUnallocatedSpace() throws IOException;
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/**
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* Tells whether or not this file store supports the file attributes
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* identified by the given file attribute view.
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*
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* <p> Invoking this method to test if the file store supports {@link
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* BasicFileAttributeView} will always return {@code true}. In the case of
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* the default provider, this method cannot guarantee to give the correct
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* result when the file store is not a local storage device. The reasons for
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* this are implementation specific and therefore unspecified.
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*
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* @param type
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* the file attribute view type
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*
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* @return {@code true} if, and only if, the file attribute view is
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* supported
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*/
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public abstract boolean supportsFileAttributeView(Class<? extends FileAttributeView> type);
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/**
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* Tells whether or not this file store supports the file attributes
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* identified by the given file attribute view.
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*
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* <p> Invoking this method to test if the file store supports {@link
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* BasicFileAttributeView}, identified by the name "{@code basic}" will
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* always return {@code true}. In the case of the default provider, this
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* method cannot guarantee to give the correct result when the file store is
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* not a local storage device. The reasons for this are implementation
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* specific and therefore unspecified.
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*
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* @param name
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* the {@link FileAttributeView#name name} of file attribute view
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*
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* @return {@code true} if, and only if, the file attribute view is
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* supported
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*/
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public abstract boolean supportsFileAttributeView(String name);
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/**
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* Returns a {@code FileStoreAttributeView} of the given type.
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*
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* <p> This method is intended to be used where the file store attribute
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* view defines type-safe methods to read or update the file store attributes.
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* The {@code type} parameter is the type of the attribute view required and
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* the method returns an instance of that type if supported.
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*
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* @param <V>
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* The {@code FileStoreAttributeView} type
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* @param type
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* the {@code Class} object corresponding to the attribute view
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*
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* @return a file store attribute view of the specified type or
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* {@code null} if the attribute view is not available
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*/
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public abstract <V extends FileStoreAttributeView> V
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getFileStoreAttributeView(Class<V> type);
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/**
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* Reads the value of a file store attribute.
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*
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* <p> The {@code attribute} parameter identifies the attribute to be read
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* and takes the form:
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* <blockquote>
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* <i>view-name</i><b>:</b><i>attribute-name</i>
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* </blockquote>
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* where the character {@code ':'} stands for itself.
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*
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* <p> <i>view-name</i> is the {@link FileStoreAttributeView#name name} of
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* a {@link FileStore AttributeView} that identifies a set of file attributes.
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* <i>attribute-name</i> is the name of the attribute.
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*
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* <p> <b>Usage Example:</b>
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* Suppose we want to know if ZFS compression is enabled (assuming the "zfs"
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* view is supported):
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* <pre>
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* boolean compression = (Boolean)fs.getAttribute("zfs:compression");
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* </pre>
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*
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* @param attribute
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* the attribute to read
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* @return the attribute value; {@code null} may be valid for some
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* attributes
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*
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* @throws UnsupportedOperationException
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* if the attribute view is not available or it does not support
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* reading the attribute
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* @throws IOException
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* if an I/O error occurs
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*/
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public abstract Object getAttribute(String attribute) throws IOException;
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}
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