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	/*
	* Copyright (c) 2007, 2018, 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.io.File;
	import java.io.IOException;
	import java.net.URI;
	import java.nio.file.spi.FileSystemProvider;
	import java.util.Iterator;
	import java.util.NoSuchElementException;

	/**
	* An object that may be used to locate a file in a file system. It will
	* typically represent a system dependent file path.
	*
	* <p> A {@code Path} represents a path that is hierarchical and composed of a
	* sequence of directory and file name elements separated by a special separator
	* or delimiter. A <em>root component</em>, that identifies a file system
	* hierarchy, may also be present. The name element that is <em>farthest</em>
	* from the root of the directory hierarchy is the name of a file or directory.
	* The other name elements are directory names. A {@code Path} can represent a
	* root, a root and a sequence of names, or simply one or more name elements.
	* A {@code Path} is considered to be an <i>empty path</i> if it consists
	* solely of one name element that is empty. Accessing a file using an
	* <i>empty path</i> is equivalent to accessing the default directory of the
	* file system. {@code Path} defines the {@link #getFileName() getFileName},
	* {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath
	* subpath} methods to access the path components or a subsequence of its name
	* elements.
	*
	* <p> In addition to accessing the components of a path, a {@code Path} also
	* defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
	* resolveSibling} methods to combine paths. The {@link #relativize relativize}
	* method that can be used to construct a relative path between two paths.
	* Paths can be {@link #compareTo compared}, and tested against each other using
	* the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods.
	*
	* <p> This interface extends {@link Watchable} interface so that a directory
	* located by a path can be {@link #register registered} with a {@link
	* WatchService} and entries in the directory watched. </p>
	*
	* <p> <b>WARNING:</b> This interface is only intended to be implemented by
	* those developing custom file system implementations. Methods may be added to
	* this interface in future releases. </p>
	*
	* <h2>Accessing Files</h2>
	* <p> Paths may be used with the {@link Files} class to operate on files,
	* directories, and other types of files. For example, suppose we want a {@link
	* java.io.BufferedReader} to read text from a file "{@code access.log}". The
	* file is located in a directory "{@code logs}" relative to the current working
	* directory and is UTF-8 encoded.
	* <pre>
	* Path path = FileSystems.getDefault().getPath("logs", "access.log");
	* BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
	* </pre>
	*
	* <a id="interop"></a><h2>Interoperability</h2>
	* <p> Paths associated with the default {@link
	* java.nio.file.spi.FileSystemProvider provider} are generally interoperable
	* with the {@link java.io.File java.io.File} class. Paths created by other
	* providers are unlikely to be interoperable with the abstract path names
	* represented by {@code java.io.File}. The {@link java.io.File#toPath toPath}
	* method may be used to obtain a {@code Path} from the abstract path name
	* represented by a {@code java.io.File} object. The resulting {@code Path} can
	* be used to operate on the same file as the {@code java.io.File} object. In
	* addition, the {@link #toFile toFile} method is useful to construct a {@code
	* File} from the {@code String} representation of a {@code Path}.
	*
	* <h2>Concurrency</h2>
	* <p> Implementations of this interface are immutable and safe for use by
	* multiple concurrent threads.
	*
	* @since 1.7
	*/

	public interface Path
	extends Comparable<Path>, Iterable<Path>, Watchable
	{
	/**
	* Returns a {@code Path} by converting a path string, or a sequence of
	* strings that when joined form a path string. If {@code more} does not
	* specify any elements then the value of the {@code first} parameter is
	* the path string to convert. If {@code more} specifies one or more
	* elements then each non-empty string, including {@code first}, is
	* considered to be a sequence of name elements and is joined to form a
	* path string. The details as to how the Strings are joined is provider
	* specific but typically they will be joined using the
	* {@link FileSystem#getSeparator name-separator} as the separator.
	* For example, if the name separator is "{@code /}" and
	* {@code getPath("/foo","bar","gus")} is invoked, then the path string
	* {@code "/foo/bar/gus"} is converted to a {@code Path}. A {@code Path}
	* representing an empty path is returned if {@code first} is the empty
	* string and {@code more} does not contain any non-empty strings.
	*
	* <p> The {@code Path} is obtained by invoking the {@link FileSystem#getPath
	* getPath} method of the {@link FileSystems#getDefault default} {@link
	* FileSystem}.
	*
	* <p> Note that while this method is very convenient, using it will imply
	* an assumed reference to the default {@code FileSystem} and limit the
	* utility of the calling code. Hence it should not be used in library code
	* intended for flexible reuse. A more flexible alternative is to use an
	* existing {@code Path} instance as an anchor, such as:
	* <pre>{@code
	* Path dir = ...
	* Path path = dir.resolve("file");
	* }</pre>
	*
	* @param first
	* the path string or initial part of the path string
	* @param more
	* additional strings to be joined to form the path string
	*
	* @return the resulting {@code Path}
	*
	* @throws InvalidPathException
	* if the path string cannot be converted to a {@code Path}
	*
	* @see FileSystem#getPath
	*
	* @since 11
	*/
	public static Path of(String first, String... more) {
	return FileSystems.getDefault().getPath(first, more);
	}

	/**
	* Returns a {@code Path} by converting a URI.
	*
	* <p> This method iterates over the {@link FileSystemProvider#installedProviders()
	* installed} providers to locate the provider that is identified by the
	* URI {@link URI#getScheme scheme} of the given URI. URI schemes are
	* compared without regard to case. If the provider is found then its {@link
	* FileSystemProvider#getPath getPath} method is invoked to convert the
	* URI.
	*
	* <p> In the case of the default provider, identified by the URI scheme
	* "file", the given URI has a non-empty path component, and undefined query
	* and fragment components. Whether the authority component may be present
	* is platform specific. The returned {@code Path} is associated with the
	* {@link FileSystems#getDefault default} file system.
	*
	* <p> The default provider provides a similar <em>round-trip</em> guarantee
	* to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
	* is guaranteed that
	* <blockquote>{@code
	* Path.of(}<i>p</i>{@code .}{@link Path#toUri() toUri}{@code ()).equals(}
	* <i>p</i>{@code .}{@link Path#toAbsolutePath() toAbsolutePath}{@code ())}
	* </blockquote>
	* so long as the original {@code Path}, the {@code URI}, and the new {@code
	* Path} are all created in (possibly different invocations of) the same
	* Java virtual machine. Whether other providers make any guarantees is
	* provider specific and therefore unspecified.
	*
	* @param uri
	* the URI to convert
	*
	* @return the resulting {@code Path}
	*
	* @throws IllegalArgumentException
	* if preconditions on the {@code uri} parameter do not hold. The
	* format of the URI is provider specific.
	* @throws FileSystemNotFoundException
	* The file system, identified by the URI, does not exist and
	* cannot be created automatically, or the provider identified by
	* the URI's scheme component is not installed
	* @throws SecurityException
	* if a security manager is installed and it denies an unspecified
	* permission to access the file system
	*
	* @since 11
	*/
	public static Path of(URI uri) {
	String scheme = uri.getScheme();
	if (scheme == null)
	throw new IllegalArgumentException("Missing scheme");

	// check for default provider to avoid loading of installed providers
	if (scheme.equalsIgnoreCase("file"))
	return FileSystems.getDefault().provider().getPath(uri);

	// try to find provider
	for (FileSystemProvider provider: FileSystemProvider.installedProviders()) {
	if (provider.getScheme().equalsIgnoreCase(scheme)) {
	return provider.getPath(uri);
	}
	}

	throw new FileSystemNotFoundException("Provider \"" + scheme + "\" not installed");
	}

	/**
	* Returns the file system that created this object.
	*
	* @return the file system that created this object
	*/
	FileSystem getFileSystem();

	/**
	* Tells whether or not this path is absolute.
	*
	* <p> An absolute path is complete in that it doesn't need to be combined
	* with other path information in order to locate a file.
	*
	* @return {@code true} if, and only if, this path is absolute
	*/
	boolean isAbsolute();

	/**
	* Returns the root component of this path as a {@code Path} object,
	* or {@code null} if this path does not have a root component.
	*
	* @return a path representing the root component of this path,
	* or {@code null}
	*/
	Path getRoot();

	/**
	* Returns the name of the file or directory denoted by this path as a
	* {@code Path} object. The file name is the <em>farthest</em> element from
	* the root in the directory hierarchy.
	*
	* @return a path representing the name of the file or directory, or
	* {@code null} if this path has zero elements
	*/
	Path getFileName();

	/**
	* Returns the <em>parent path</em>, or {@code null} if this path does not
	* have a parent.
	*
	* <p> The parent of this path object consists of this path's root
	* component, if any, and each element in the path except for the
	* <em>farthest</em> from the root in the directory hierarchy. This method
	* does not access the file system; the path or its parent may not exist.
	* Furthermore, this method does not eliminate special names such as "."
	* and ".." that may be used in some implementations. On UNIX for example,
	* the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of
	* {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link
	* #normalize normalize} method, to eliminate redundant names, for cases where
	* <em>shell-like</em> navigation is required.
	*
	* <p> If this path has more than one element, and no root component, then
	* this method is equivalent to evaluating the expression:
	* <blockquote><pre>
	* subpath(0, getNameCount()-1);
	* </pre></blockquote>
	*
	* @return a path representing the path's parent
	*/
	Path getParent();

	/**
	* Returns the number of name elements in the path.
	*
	* @return the number of elements in the path, or {@code 0} if this path
	* only represents a root component
	*/
	int getNameCount();

	/**
	* Returns a name element of this path as a {@code Path} object.
	*
	* <p> The {@code index} parameter is the index of the name element to return.
	* The element that is <em>closest</em> to the root in the directory hierarchy
	* has index {@code 0}. The element that is <em>farthest</em> from the root
	* has index {@link #getNameCount count}{@code -1}.
	*
	* @param index
	* the index of the element
	*
	* @return the name element
	*
	* @throws IllegalArgumentException
	* if {@code index} is negative, {@code index} is greater than or
	* equal to the number of elements, or this path has zero name
	* elements
	*/
	Path getName(int index);

	/**
	* Returns a relative {@code Path} that is a subsequence of the name
	* elements of this path.
	*
	* <p> The {@code beginIndex} and {@code endIndex} parameters specify the
	* subsequence of name elements. The name that is <em>closest</em> to the root
	* in the directory hierarchy has index {@code 0}. The name that is
	* <em>farthest</em> from the root has index {@link #getNameCount
	* count}{@code -1}. The returned {@code Path} object has the name elements
	* that begin at {@code beginIndex} and extend to the element at index {@code
	* endIndex-1}.
	*
	* @param beginIndex
	* the index of the first element, inclusive
	* @param endIndex
	* the index of the last element, exclusive
	*
	* @return a new {@code Path} object that is a subsequence of the name
	* elements in this {@code Path}
	*
	* @throws IllegalArgumentException
	* if {@code beginIndex} is negative, or greater than or equal to
	* the number of elements. If {@code endIndex} is less than or
	* equal to {@code beginIndex}, or larger than the number of elements.
	*/
	Path subpath(int beginIndex, int endIndex);

	/**
	* Tests if this path starts with the given path.
	*
	* <p> This path <em>starts</em> with the given path if this path's root
	* component <em>starts</em> with the root component of the given path,
	* and this path starts with the same name elements as the given path.
	* If the given path has more name elements than this path then {@code false}
	* is returned.
	*
	* <p> Whether or not the root component of this path starts with the root
	* component of the given path is file system specific. If this path does
	* not have a root component and the given path has a root component then
	* this path does not start with the given path.
	*
	* <p> If the given path is associated with a different {@code FileSystem}
	* to this path then {@code false} is returned.
	*
	* @param other
	* the given path
	*
	* @return {@code true} if this path starts with the given path; otherwise
	* {@code false}
	*/
	boolean startsWith(Path other);

	/**
	* Tests if this path starts with a {@code Path}, constructed by converting
	* the given path string, in exactly the manner specified by the {@link
	* #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path
	* "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It
	* does not start with "{@code f}" or "{@code fo}".
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* startsWith(getFileSystem().getPath(other));
	* }</pre>
	*
	* @param other
	* the given path string
	*
	* @return {@code true} if this path starts with the given path; otherwise
	* {@code false}
	*
	* @throws InvalidPathException
	* If the path string cannot be converted to a Path.
	*/
	default boolean startsWith(String other) {
	return startsWith(getFileSystem().getPath(other));
	}

	/**
	* Tests if this path ends with the given path.
	*
	* <p> If the given path has <em>N</em> elements, and no root component,
	* and this path has <em>N</em> or more elements, then this path ends with
	* the given path if the last <em>N</em> elements of each path, starting at
	* the element farthest from the root, are equal.
	*
	* <p> If the given path has a root component then this path ends with the
	* given path if the root component of this path <em>ends with</em> the root
	* component of the given path, and the corresponding elements of both paths
	* are equal. Whether or not the root component of this path ends with the
	* root component of the given path is file system specific. If this path
	* does not have a root component and the given path has a root component
	* then this path does not end with the given path.
	*
	* <p> If the given path is associated with a different {@code FileSystem}
	* to this path then {@code false} is returned.
	*
	* @param other
	* the given path
	*
	* @return {@code true} if this path ends with the given path; otherwise
	* {@code false}
	*/
	boolean endsWith(Path other);

	/**
	* Tests if this path ends with a {@code Path}, constructed by converting
	* the given path string, in exactly the manner specified by the {@link
	* #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path
	* "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does
	* not end with "{@code r}" or "{@code /bar}". Note that trailing separators
	* are not taken into account, and so invoking this method on the {@code
	* Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns
	* {@code true}.
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* endsWith(getFileSystem().getPath(other));
	* }</pre>
	*
	* @param other
	* the given path string
	*
	* @return {@code true} if this path ends with the given path; otherwise
	* {@code false}
	*
	* @throws InvalidPathException
	* If the path string cannot be converted to a Path.
	*/
	default boolean endsWith(String other) {
	return endsWith(getFileSystem().getPath(other));
	}

	/**
	* Returns a path that is this path with redundant name elements eliminated.
	*
	* <p> The precise definition of this method is implementation dependent but
	* in general it derives from this path, a path that does not contain
	* <em>redundant</em> name elements. In many file systems, the "{@code .}"
	* and "{@code ..}" are special names used to indicate the current directory
	* and parent directory. In such file systems all occurrences of "{@code .}"
	* are considered redundant. If a "{@code ..}" is preceded by a
	* non-"{@code ..}" name then both names are considered redundant (the
	* process to identify such names is repeated until it is no longer
	* applicable).
	*
	* <p> This method does not access the file system; the path may not locate
	* a file that exists. Eliminating "{@code ..}" and a preceding name from a
	* path may result in the path that locates a different file than the original
	* path. This can arise when the preceding name is a symbolic link.
	*
	* @return the resulting path or this path if it does not contain
	* redundant name elements; an empty path is returned if this path
	* does not have a root component and all name elements are redundant
	*
	* @see #getParent
	* @see #toRealPath
	*/
	Path normalize();

	// -- resolution and relativization --

	/**
	* Resolve the given path against this path.
	*
	* <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
	* path then this method trivially returns {@code other}. If {@code other}
	* is an <i>empty path</i> then this method trivially returns this path.
	* Otherwise this method considers this path to be a directory and resolves
	* the given path against this path. In the simplest case, the given path
	* does not have a {@link #getRoot root} component, in which case this method
	* <em>joins</em> the given path to this path and returns a resulting path
	* that {@link #endsWith ends} with the given path. Where the given path has
	* a root component then resolution is highly implementation dependent and
	* therefore unspecified.
	*
	* @param other
	* the path to resolve against this path
	*
	* @return the resulting path
	*
	* @see #relativize
	*/
	Path resolve(Path other);

	/**
	* Converts a given path string to a {@code Path} and resolves it against
	* this {@code Path} in exactly the manner specified by the {@link
	* #resolve(Path) resolve} method. For example, suppose that the name
	* separator is "{@code /}" and a path represents "{@code foo/bar}", then
	* invoking this method with the path string "{@code gus}" will result in
	* the {@code Path} "{@code foo/bar/gus}".
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* resolve(getFileSystem().getPath(other));
	* }</pre>
	*
	* @param other
	* the path string to resolve against this path
	*
	* @return the resulting path
	*
	* @throws InvalidPathException
	* if the path string cannot be converted to a Path.
	*
	* @see FileSystem#getPath
	*/
	default Path resolve(String other) {
	return resolve(getFileSystem().getPath(other));
	}

	/**
	* Resolves the given path against this path's {@link #getParent parent}
	* path. This is useful where a file name needs to be <i>replaced</i> with
	* another file name. For example, suppose that the name separator is
	* "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking
	* this method with the {@code Path} "{@code bar}" will result in the {@code
	* Path} "{@code dir1/dir2/bar}". If this path does not have a parent path,
	* or {@code other} is {@link #isAbsolute() absolute}, then this method
	* returns {@code other}. If {@code other} is an empty path then this method
	* returns this path's parent, or where this path doesn't have a parent, the
	* empty path.
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* (getParent() == null) ? other : getParent().resolve(other);
	* }</pre>
	* unless {@code other == null}, in which case a
	* {@code NullPointerException} is thrown.
	*
	* @param other
	* the path to resolve against this path's parent
	*
	* @return the resulting path
	*
	* @see #resolve(Path)
	*/
	default Path resolveSibling(Path other) {
	if (other == null)
	throw new NullPointerException();
	Path parent = getParent();
	return (parent == null) ? other : parent.resolve(other);
	}

	/**
	* Converts a given path string to a {@code Path} and resolves it against
	* this path's {@link #getParent parent} path in exactly the manner
	* specified by the {@link #resolveSibling(Path) resolveSibling} method.
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* resolveSibling(getFileSystem().getPath(other));
	* }</pre>
	*
	* @param other
	* the path string to resolve against this path's parent
	*
	* @return the resulting path
	*
	* @throws InvalidPathException
	* if the path string cannot be converted to a Path.
	*
	* @see FileSystem#getPath
	*/
	default Path resolveSibling(String other) {
	return resolveSibling(getFileSystem().getPath(other));
	}

	/**
	* Constructs a relative path between this path and a given path.
	*
	* <p> Relativization is the inverse of {@link #resolve(Path) resolution}.
	* This method attempts to construct a {@link #isAbsolute relative} path
	* that when {@link #resolve(Path) resolved} against this path, yields a
	* path that locates the same file as the given path. For example, on UNIX,
	* if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"}
	* then the resulting relative path would be {@code "c/d"}. Where this
	* path and the given path do not have a {@link #getRoot root} component,
	* then a relative path can be constructed. A relative path cannot be
	* constructed if only one of the paths have a root component. Where both
	* paths have a root component then it is implementation dependent if a
	* relative path can be constructed. If this path and the given path are
	* {@link #equals equal} then an <i>empty path</i> is returned.
	*
	* <p> For any two {@link #normalize normalized} paths <i>p</i> and
	* <i>q</i>, where <i>q</i> does not have a root component,
	* <blockquote>
	* <i>p</i>{@code .relativize(}<i>p</i>
	* {@code .resolve(}<i>q</i>{@code )).equals(}<i>q</i>{@code )}
	* </blockquote>
	*
	* <p> When symbolic links are supported, then whether the resulting path,
	* when resolved against this path, yields a path that can be used to locate
	* the {@link Files#isSameFile same} file as {@code other} is implementation
	* dependent. For example, if this path is {@code "/a/b"} and the given
	* path is {@code "/a/x"} then the resulting relative path may be {@code
	* "../x"}. If {@code "b"} is a symbolic link then is implementation
	* dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}.
	*
	* @param other
	* the path to relativize against this path
	*
	* @return the resulting relative path, or an empty path if both paths are
	* equal
	*
	* @throws IllegalArgumentException
	* if {@code other} is not a {@code Path} that can be relativized
	* against this path
	*/
	Path relativize(Path other);

	/**
	* Returns a URI to represent this path.
	*
	* <p> This method constructs an absolute {@link URI} with a {@link
	* URI#getScheme() scheme} equal to the URI scheme that identifies the
	* provider. The exact form of the scheme specific part is highly provider
	* dependent.
	*
	* <p> In the case of the default provider, the URI is hierarchical with
	* a {@link URI#getPath() path} component that is absolute. The query and
	* fragment components are undefined. Whether the authority component is
	* defined or not is implementation dependent. There is no guarantee that
	* the {@code URI} may be used to construct a {@link java.io.File java.io.File}.
	* In particular, if this path represents a Universal Naming Convention (UNC)
	* path, then the UNC server name may be encoded in the authority component
	* of the resulting URI. In the case of the default provider, and the file
	* exists, and it can be determined that the file is a directory, then the
	* resulting {@code URI} will end with a slash.
	*
	* <p> The default provider provides a similar <em>round-trip</em> guarantee
	* to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
	* is guaranteed that
	* <blockquote>
	* {@link Path#of(URI) Path.of}{@code (}<i>p</i>{@code .toUri()).equals(}<i>p</i>
	* {@code .}{@link #toAbsolutePath() toAbsolutePath}{@code ())}
	* </blockquote>
	* so long as the original {@code Path}, the {@code URI}, and the new {@code
	* Path} are all created in (possibly different invocations of) the same
	* Java virtual machine. Whether other providers make any guarantees is
	* provider specific and therefore unspecified.
	*
	* <p> When a file system is constructed to access the contents of a file
	* as a file system then it is highly implementation specific if the returned
	* URI represents the given path in the file system or it represents a
	* <em>compound</em> URI that encodes the URI of the enclosing file system.
	* A format for compound URIs is not defined in this release; such a scheme
	* may be added in a future release.
	*
	* @return the URI representing this path
	*
	* @throws java.io.IOError
	* if an I/O error occurs obtaining the absolute path, or where a
	* file system is constructed to access the contents of a file as
	* a file system, and the URI of the enclosing file system cannot be
	* obtained
	*
	* @throws SecurityException
	* In the case of the default provider, and a security manager
	* is installed, the {@link #toAbsolutePath toAbsolutePath} method
	* throws a security exception.
	*/
	URI toUri();

	/**
	* Returns a {@code Path} object representing the absolute path of this
	* path.
	*
	* <p> If this path is already {@link Path#isAbsolute absolute} then this
	* method simply returns this path. Otherwise, this method resolves the path
	* in an implementation dependent manner, typically by resolving the path
	* against a file system default directory. Depending on the implementation,
	* this method may throw an I/O error if the file system is not accessible.
	*
	* @return a {@code Path} object representing the absolute path
	*
	* @throws java.io.IOError
	* if an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, a security manager
	* is installed, and this path is not absolute, then the security
	* manager's {@link SecurityManager#checkPropertyAccess(String)
	* checkPropertyAccess} method is invoked to check access to the
	* system property {@code user.dir}
	*/
	Path toAbsolutePath();

	/**
	* Returns the <em>real</em> path of an existing file.
	*
	* <p> The precise definition of this method is implementation dependent but
	* in general it derives from this path, an {@link #isAbsolute absolute}
	* path that locates the {@link Files#isSameFile same} file as this path, but
	* with name elements that represent the actual name of the directories
	* and the file. For example, where filename comparisons on a file system
	* are case insensitive then the name elements represent the names in their
	* actual case. Additionally, the resulting path has redundant name
	* elements removed.
	*
	* <p> If this path is relative then its absolute path is first obtained,
	* as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
	*
	* <p> The {@code options} array may be used to indicate how symbolic links
	* are handled. By default, symbolic links are resolved to their final
	* target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is
	* present then this method does not resolve symbolic links.
	*
	* Some implementations allow special names such as "{@code ..}" to refer to
	* the parent directory. When deriving the <em>real path</em>, and a
	* "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then
	* an implementation will typically cause both names to be removed. When
	* not resolving symbolic links and the preceding name is a symbolic link
	* then the names are only removed if it guaranteed that the resulting path
	* will locate the same file as this path.
	*
	* @param options
	* options indicating how symbolic links are handled
	*
	* @return an absolute path represent the <em>real</em> path of the file
	* located by this object
	*
	* @throws IOException
	* if the file does not exist or an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, and a security manager
	* is installed, its {@link SecurityManager#checkRead(String) checkRead}
	* method is invoked to check read access to the file, and where
	* this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String)
	* checkPropertyAccess} method is invoked to check access to the
	* system property {@code user.dir}
	*/
	Path toRealPath(LinkOption... options) throws IOException;

	/**
	* Returns a {@link File} object representing this path. Where this {@code
	* Path} is associated with the default provider, then this method is
	* equivalent to returning a {@code File} object constructed with the
	* {@code String} representation of this path.
	*
	* <p> If this path was created by invoking the {@code File} {@link
	* File#toPath toPath} method then there is no guarantee that the {@code
	* File} object returned by this method is {@link #equals equal} to the
	* original {@code File}.
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* new File(toString());
	* }</pre>
	* if the {@code FileSystem} which created this {@code Path} is the default
	* file system; otherwise an {@code UnsupportedOperationException} is
	* thrown.
	*
	* @return a {@code File} object representing this path
	*
	* @throws UnsupportedOperationException
	* if this {@code Path} is not associated with the default provider
	*/
	default File toFile() {
	if (getFileSystem() == FileSystems.getDefault()) {
	return new File(toString());
	} else {
	throw new UnsupportedOperationException("Path not associated with "
	+ "default file system.");
	}
	}

	// -- watchable --

	/**
	* Registers the file located by this path with a watch service.
	*
	* <p> In this release, this path locates a directory that exists. The
	* directory is registered with the watch service so that entries in the
	* directory can be watched. The {@code events} parameter is the events to
	* register and may contain the following events:
	* <ul>
	* <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
	* entry created or moved into the directory</li>
	* <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
	* entry deleted or moved out of the directory</li>
	* <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
	* entry in directory was modified</li>
	* </ul>
	*
	* <p> The {@link WatchEvent#context context} for these events is the
	* relative path between the directory located by this path, and the path
	* that locates the directory entry that is created, deleted, or modified.
	*
	* <p> The set of events may include additional implementation specific
	* event that are not defined by the enum {@link StandardWatchEventKinds}
	*
	* <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
	* qualify how the directory is registered. This release does not define any
	* <em>standard</em> modifiers. It may contain implementation specific
	* modifiers.
	*
	* <p> Where a file is registered with a watch service by means of a symbolic
	* link then it is implementation specific if the watch continues to depend
	* on the existence of the symbolic link after it is registered.
	*
	* @param watcher
	* the watch service to which this object is to be registered
	* @param events
	* the events for which this object should be registered
	* @param modifiers
	* the modifiers, if any, that modify how the object is registered
	*
	* @return a key representing the registration of this object with the
	* given watch service
	*
	* @throws UnsupportedOperationException
	* if unsupported events or modifiers are specified
	* @throws IllegalArgumentException
	* if an invalid combination of events or modifiers is specified
	* @throws ClosedWatchServiceException
	* if the watch service is closed
	* @throws NotDirectoryException
	* if the file is registered to watch the entries in a directory
	* and the file is not a directory <i>(optional specific exception)</i>
	* @throws IOException
	* if an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, and a security manager is
	* installed, the {@link SecurityManager#checkRead(String) checkRead}
	* method is invoked to check read access to the file.
	*/
	@Override
	WatchKey register(WatchService watcher,
	WatchEvent.Kind<?>[] events,
	WatchEvent.Modifier... modifiers)
	throws IOException;

	/**
	* Registers the file located by this path with a watch service.
	*
	* <p> An invocation of this method behaves in exactly the same way as the
	* invocation
	* <pre>
	* watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
	* </pre>
	*
	* <p> <b>Usage Example:</b>
	* Suppose we wish to register a directory for entry create, delete, and modify
	* events:
	* <pre>
	* Path dir = ...
	* WatchService watcher = ...
	*
	* WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
	* </pre>
	*
	* @implSpec
	* The default implementation is equivalent for this path to:
	* <pre>{@code
	* register(watcher, events, new WatchEvent.Modifier[0]);
	* }</pre>
	*
	* @param watcher
	* The watch service to which this object is to be registered
	* @param events
	* The events for which this object should be registered
	*
	* @return A key representing the registration of this object with the
	* given watch service
	*
	* @throws UnsupportedOperationException
	* If unsupported events are specified
	* @throws IllegalArgumentException
	* If an invalid combination of events is specified
	* @throws ClosedWatchServiceException
	* If the watch service is closed
	* @throws NotDirectoryException
	* If the file is registered to watch the entries in a directory
	* and the file is not a directory <i>(optional specific exception)</i>
	* @throws IOException
	* If an I/O error occurs
	* @throws SecurityException
	* In the case of the default provider, and a security manager is
	* installed, the {@link SecurityManager#checkRead(String) checkRead}
	* method is invoked to check read access to the file.
	*/
	@Override
	default WatchKey register(WatchService watcher,
	WatchEvent.Kind<?>... events) throws IOException {
	return register(watcher, events, new WatchEvent.Modifier[0]);
	}

	// -- Iterable --

	/**
	* Returns an iterator over the name elements of this path.
	*
	* <p> The first element returned by the iterator represents the name
	* element that is closest to the root in the directory hierarchy, the
	* second element is the next closest, and so on. The last element returned
	* is the name of the file or directory denoted by this path. The {@link
	* #getRoot root} component, if present, is not returned by the iterator.
	*
	* @implSpec
	* The default implementation returns an {@code Iterator<Path>} which, for
	* this path, traverses the {@code Path}s returned by
	* {@code getName(index)}, where {@code index} ranges from zero to
	* {@code getNameCount() - 1}, inclusive.
	*
	* @return an iterator over the name elements of this path.
	*/
	@Override
	default Iterator<Path> iterator() {
	return new Iterator<>() {
	private int i = 0;

	@Override
	public boolean hasNext() {
	return (i < getNameCount());
	}

	@Override
	public Path next() {
	if (i < getNameCount()) {
	Path result = getName(i);
	i++;
	return result;
	} else {
	throw new NoSuchElementException();
	}
	}
	};
	}

	// -- compareTo/equals/hashCode --

	/**
	* Compares two abstract paths lexicographically. The ordering defined by
	* this method is provider specific, and in the case of the default
	* provider, platform specific. This method does not access the file system
	* and neither file is required to exist.
	*
	* <p> This method may not be used to compare paths that are associated
	* with different file system providers.
	*
	* @param other the path compared to this path.
	*
	* @return zero if the argument is {@link #equals equal} to this path, a
	* value less than zero if this path is lexicographically less than
	* the argument, or a value greater than zero if this path is
	* lexicographically greater than the argument
	*
	* @throws ClassCastException
	* if the paths are associated with different providers
	*/
	@Override
	int compareTo(Path other);

	/**
	* Tests this path for equality with the given object.
	*
	* <p> If the given object is not a Path, or is a Path associated with a
	* different {@code FileSystem}, then this method returns {@code false}.
	*
	* <p> Whether or not two path are equal depends on the file system
	* implementation. In some cases the paths are compared without regard
	* to case, and others are case sensitive. This method does not access the
	* file system and the file is not required to exist. Where required, the
	* {@link Files#isSameFile isSameFile} method may be used to check if two
	* paths locate the same file.
	*
	* <p> This method satisfies the general contract of the {@link
	* java.lang.Object#equals(Object) Object.equals} method. </p>
	*
	* @param other
	* the object to which this object is to be compared
	*
	* @return {@code true} if, and only if, the given object is a {@code Path}
	* that is identical to this {@code Path}
	*/
	boolean equals(Object other);

	/**
	* Computes a hash code for this path.
	*
	* <p> The hash code is based upon the components of the path, and
	* satisfies the general contract of the {@link Object#hashCode
	* Object.hashCode} method.
	*
	* @return the hash-code value for this path
	*/
	int hashCode();

	/**
	* Returns the string representation of this path.
	*
	* <p> If this path was created by converting a path string using the
	* {@link FileSystem#getPath getPath} method then the path string returned
	* by this method may differ from the original String used to create the path.
	*
	* <p> The returned path string uses the default name {@link
	* FileSystem#getSeparator separator} to separate names in the path.
	*
	* @return the string representation of this path
	*/
	String toString();
	}

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