202 lines
8.6 KiB
Java
202 lines
8.6 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.attribute;
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import java.nio.file.*;
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import java.util.Set;
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import java.io.IOException;
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/**
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* A file attribute view that provides a view of the file attributes commonly
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* associated with files on file systems used by operating systems that implement
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* the Portable Operating System Interface (POSIX) family of standards.
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*
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* <p> Operating systems that implement the <a href="http://www.opengroup.org">
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* POSIX</a> family of standards commonly use file systems that have a
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* file <em>owner</em>, <em>group-owner</em>, and related <em>access
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* permissions</em>. This file attribute view provides read and write access
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* to these attributes.
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*
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* <p> The {@link #readAttributes() readAttributes} method is used to read the
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* file's attributes. The file {@link PosixFileAttributes#owner() owner} is
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* represented by a {@link UserPrincipal} that is the identity of the file owner
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* for the purposes of access control. The {@link PosixFileAttributes#group()
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* group-owner}, represented by a {@link GroupPrincipal}, is the identity of the
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* group owner, where a group is an identity created for administrative purposes
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* so as to determine the access rights for the members of the group.
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*
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* <p> The {@link PosixFileAttributes#permissions() permissions} attribute is a
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* set of access permissions. This file attribute view provides access to the nine
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* permission defined by the {@link PosixFilePermission} class.
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* These nine permission bits determine the <em>read</em>, <em>write</em>, and
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* <em>execute</em> access for the file owner, group, and others (others
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* meaning identities other than the owner and members of the group). Some
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* operating systems and file systems may provide additional permission bits
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* but access to these other bits is not defined by this class in this release.
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*
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* <p> <b>Usage Example:</b>
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* Suppose we need to print out the owner and access permissions of a file:
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* <pre>
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* Path file = ...
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* PosixFileAttributes attrs = Files.getFileAttributeView(file, PosixFileAttributeView.class)
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* .readAttributes();
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* System.out.format("%s %s%n",
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* attrs.owner().getName(),
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* PosixFilePermissions.toString(attrs.permissions()));
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* </pre>
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*
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* <h2> Dynamic Access </h2>
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* <p> Where dynamic access to file attributes is required, the attributes
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* supported by this attribute view are as defined by {@link
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* BasicFileAttributeView} and {@link FileOwnerAttributeView}, and in addition,
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* the following attributes are supported:
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* <blockquote>
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* <table class="striped">
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* <caption style="display:none">Supported attributes</caption>
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* <thead>
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* <tr>
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* <th scope="col"> Name </th>
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* <th scope="col"> Type </th>
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* </tr>
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* </thead>
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* <tbody>
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* <tr>
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* <th scope="row"> "permissions" </th>
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* <td> {@link Set}<{@link PosixFilePermission}> </td>
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* </tr>
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* <tr>
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* <th scope="row"> "group" </th>
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* <td> {@link GroupPrincipal} </td>
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* </tr>
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* </tbody>
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* </table>
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* </blockquote>
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*
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* <p> The {@link Files#getAttribute getAttribute} method may be used to read
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* any of these attributes, or any of the attributes defined by {@link
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* BasicFileAttributeView} as if by invoking the {@link #readAttributes
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* readAttributes()} method.
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*
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* <p> The {@link Files#setAttribute setAttribute} method may be used to update
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* the file's last modified time, last access time or create time attributes as
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* defined by {@link BasicFileAttributeView}. It may also be used to update
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* the permissions, owner, or group-owner as if by invoking the {@link
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* #setPermissions setPermissions}, {@link #setOwner setOwner}, and {@link
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* #setGroup setGroup} methods respectively.
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*
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* <h2> Setting Initial Permissions </h2>
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* <p> Implementations supporting this attribute view may also support setting
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* the initial permissions when creating a file or directory. The
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* initial permissions are provided to the {@link Files#createFile createFile}
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* or {@link Files#createDirectory createDirectory} methods as a {@link
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* FileAttribute} with {@link FileAttribute#name name} {@code "posix:permissions"}
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* and a {@link FileAttribute#value value} that is the set of permissions. The
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* following example uses the {@link PosixFilePermissions#asFileAttribute
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* asFileAttribute} method to construct a {@code FileAttribute} when creating a
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* file:
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*
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* <pre>
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* Path path = ...
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* Set<PosixFilePermission> perms =
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* EnumSet.of(OWNER_READ, OWNER_WRITE, OWNER_EXECUTE, GROUP_READ);
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* Files.createFile(path, PosixFilePermissions.asFileAttribute(perms));
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* </pre>
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*
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* <p> When the access permissions are set at file creation time then the actual
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* value of the permissions may differ that the value of the attribute object.
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* The reasons for this are implementation specific. On UNIX systems, for
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* example, a process has a <em>umask</em> that impacts the permission bits
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* of newly created files. Where an implementation supports the setting of
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* the access permissions, and the underlying file system supports access
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* permissions, then it is required that the value of the actual access
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* permissions will be equal or less than the value of the attribute
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* provided to the {@link Files#createFile createFile} or {@link
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* Files#createDirectory createDirectory} methods. In other words, the file may
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* be more secure than requested.
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*
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* @since 1.7
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*/
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public interface PosixFileAttributeView
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extends BasicFileAttributeView, FileOwnerAttributeView
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{
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/**
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* Returns the name of the attribute view. Attribute views of this type
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* have the name {@code "posix"}.
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*/
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@Override
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String name();
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/**
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* @throws IOException {@inheritDoc}
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* @throws SecurityException
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* In the case of the default provider, a security manager is
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* installed, and it denies
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* {@link RuntimePermission}{@code ("accessUserInformation")}
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* or its {@link SecurityManager#checkRead(String) checkRead} method
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* denies read access to the file.
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*/
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@Override
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PosixFileAttributes readAttributes() throws IOException;
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/**
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* Updates the file permissions.
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*
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* @param perms
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* the new set of permissions
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*
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* @throws ClassCastException
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* if the sets contains elements that are not of type {@code
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* PosixFilePermission}
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* @throws IOException
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* if an I/O error occurs
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* @throws SecurityException
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* In the case of the default provider, a security manager is
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* installed, and it denies
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* {@link RuntimePermission}{@code ("accessUserInformation")}
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* or its {@link SecurityManager#checkWrite(String) checkWrite}
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* method denies write access to the file.
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*/
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void setPermissions(Set<PosixFilePermission> perms) throws IOException;
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/**
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* Updates the file group-owner.
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*
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* @param group
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* the new file group-owner
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*
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* @throws IOException
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* if an I/O error occurs
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* @throws SecurityException
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* In the case of the default provider, and a security manager is
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* installed, it denies
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* {@link RuntimePermission}{@code ("accessUserInformation")}
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* or its {@link SecurityManager#checkWrite(String) checkWrite}
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* method denies write access to the file.
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*/
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void setGroup(GroupPrincipal group) throws IOException;
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}
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