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   /*
    * Copyright (c) 1994, 2013, 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.io;
  
  import java.net.URI;
  import java.net.URL;
  import java.util.List;
An abstract representation of file and directory pathnames.

User interfaces and operating systems use system-dependent pathname strings to name files and directories. This class presents an abstract, system-independent view of hierarchical pathnames. An abstract pathname has two components:

  1. An optional system-dependent prefix string, such as a disk-drive specifier, "/" for the UNIX root directory, or "\\\\" for a Microsoft Windows UNC pathname, and
  2. A sequence of zero or more string names.
The first name in an abstract pathname may be a directory name or, in the case of Microsoft Windows UNC pathnames, a hostname. Each subsequent name in an abstract pathname denotes a directory; the last name may denote either a directory or a file. The empty abstract pathname has no prefix and an empty name sequence.

The conversion of a pathname string to or from an abstract pathname is inherently system-dependent. When an abstract pathname is converted into a pathname string, each name is separated from the next by a single copy of the default separator character. The default name-separator character is defined by the system property file.separator, and is made available in the public static fields separator and separatorChar of this class. When a pathname string is converted into an abstract pathname, the names within it may be separated by the default name-separator character or by any other name-separator character that is supported by the underlying system.

A pathname, whether abstract or in string form, may be either absolute or relative. An absolute pathname is complete in that no other information is required in order to locate the file that it denotes. A relative pathname, in contrast, must be interpreted in terms of information taken from some other pathname. By default the classes in the java.io package always resolve relative pathnames against the current user directory. This directory is named by the system property user.dir, and is typically the directory in which the Java virtual machine was invoked.

The parent of an abstract pathname may be obtained by invoking the getParent() method of this class and consists of the pathname's prefix and each name in the pathname's name sequence except for the last. Each directory's absolute pathname is an ancestor of any File object with an absolute abstract pathname which begins with the directory's absolute pathname. For example, the directory denoted by the abstract pathname "/usr" is an ancestor of the directory denoted by the pathname "/usr/local/bin".

The prefix concept is used to handle root directories on UNIX platforms, and drive specifiers, root directories and UNC pathnames on Microsoft Windows platforms, as follows:

  • For UNIX platforms, the prefix of an absolute pathname is always "/". Relative pathnames have no prefix. The abstract pathname denoting the root directory has the prefix "/" and an empty name sequence.
  • For Microsoft Windows platforms, the prefix of a pathname that contains a drive specifier consists of the drive letter followed by ":" and possibly followed by "\\" if the pathname is absolute. The prefix of a UNC pathname is "\\\\"; the hostname and the share name are the first two names in the name sequence. A relative pathname that does not specify a drive has no prefix.

Instances of this class may or may not denote an actual file-system object such as a file or a directory. If it does denote such an object then that object resides in a partition. A partition is an operating system-specific portion of storage for a file system. A single storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may contain multiple partitions. The object, if any, will reside on the partition named by some ancestor of the absolute form of this pathname.

A file system may implement restrictions to certain operations on the actual file-system object, such as reading, writing, and executing. These restrictions are collectively known as access permissions. The file system may have multiple sets of access permissions on a single object. For example, one set may apply to the object's owner, and another may apply to all other users. The access permissions on an object may cause some methods in this class to fail.

Instances of the File class are immutable; that is, once created, the abstract pathname represented by a File object will never change.

Interoperability with java.nio.file package

The java.nio.file package defines interfaces and classes for the Java virtual machine to access files, file attributes, and file systems. This API may be used to overcome many of the limitations of the java.io.File class. The toPath method may be used to obtain a java.nio.file.Path that uses the abstract path represented by a File object to locate a file. The resulting Path may be used with the java.nio.file.Files class to provide more efficient and extensive access to additional file operations, file attributes, and I/O exceptions to help diagnose errors when an operation on a file fails.

Author(s):
unascribed
Since:
JDK1.0
 
 
 public class File
     implements SerializableComparable<File>
 {

    
The FileSystem object representing the platform's local file system.
 
     static private FileSystem fs = FileSystem.getFileSystem();

    
This abstract pathname's normalized pathname string. A normalized pathname string uses the default name-separator character and does not contain any duplicate or redundant separators.

Serial:
 
     private String path;

    
Enum type that indicates the status of a file path.
 
     private static enum PathStatus { INVALID, CHECKED };

    
The flag indicating whether the file path is invalid.
 
     private transient PathStatus status = null;

    
Check if the file has an invalid path. Currently, the inspection of a file path is very limited, and it only covers Nul character check. Returning true means the path is definitely invalid/garbage. But returning false does not guarantee that the path is valid.

Returns:
true if the file path is invalid.
 
     final boolean isInvalid() {
         if ( == null) {
              = (this..indexOf('\u0000') < 0) ? .
                                                        : .;
         }
         return  == .;
     }

    
The length of this abstract pathname's prefix, or zero if it has no prefix.
 
     private transient int prefixLength;

    
Returns the length of this abstract pathname's prefix. For use by FileSystem classes.
 
     int getPrefixLength() {
         return ;
     }

    
The system-dependent default name-separator character. This field is initialized to contain the first character of the value of the system property file.separator. On UNIX systems the value of this field is '/'; on Microsoft Windows systems it is '\\'.

 
     public static final char separatorChar = .getSeparator();

    
The system-dependent default name-separator character, represented as a string for convenience. This string contains a single character, namely separatorChar.
 
     public static final String separator = "" + ;

    
The system-dependent path-separator character. This field is initialized to contain the first character of the value of the system property path.separator. This character is used to separate filenames in a sequence of files given as a path list. On UNIX systems, this character is ':'; on Microsoft Windows systems it is ';'.

 
     public static final char pathSeparatorChar = .getPathSeparator();

    
The system-dependent path-separator character, represented as a string for convenience. This string contains a single character, namely pathSeparatorChar.
 
     public static final String pathSeparator = "" + ;
 
 
     /* -- Constructors -- */

    
Internal constructor for already-normalized pathname strings.
 
     private File(String pathnameint prefixLength) {
         this. = pathname;
         this. = prefixLength;
     }

    
Internal constructor for already-normalized pathname strings. The parameter order is used to disambiguate this method from the public(File, String) constructor.
 
     private File(String childFile parent) {
         assert parent.path != null;
         assert (!parent.path.equals(""));
         this. = .resolve(parent.pathchild);
         this. = parent.prefixLength;
     }

    
Creates a new File instance by converting the given pathname string into an abstract pathname. If the given string is the empty string, then the result is the empty abstract pathname.

Parameters:
pathname A pathname string
Throws:
java.lang.NullPointerException If the pathname argument is null
 
     public File(String pathname) {
         if (pathname == null) {
             throw new NullPointerException();
         }
         this. = .normalize(pathname);
         this. = .prefixLength(this.);
     }
 
     /* Note: The two-argument File constructors do not interpret an empty
        parent abstract pathname as the current user directory.  An empty parent
        instead causes the child to be resolved against the system-dependent
        directory defined by the FileSystem.getDefaultParent method.  On Unix
        this default is "/", while on Microsoft Windows it is "\\".  This is required for
        compatibility with the original behavior of this class. */

    
Creates a new File instance from a parent pathname string and a child pathname string.

If parent is null then the new File instance is created as if by invoking the single-argument File constructor on the given child pathname string.

Otherwise the parent pathname string is taken to denote a directory, and the child pathname string is taken to denote either a directory or a file. If the child pathname string is absolute then it is converted into a relative pathname in a system-dependent way. If parent is the empty string then the new File instance is created by converting child into an abstract pathname and resolving the result against a system-dependent default directory. Otherwise each pathname string is converted into an abstract pathname and the child abstract pathname is resolved against the parent.

Parameters:
parent The parent pathname string
child The child pathname string
Throws:
java.lang.NullPointerException If child is null
 
     public File(String parentString child) {
         if (child == null) {
             throw new NullPointerException();
         }
         if (parent != null) {
             if (parent.equals("")) {
                 this. = .resolve(.getDefaultParent(),
                                        .normalize(child));
             } else {
                 this. = .resolve(.normalize(parent),
                                        .normalize(child));
             }
         } else {
             this. = .normalize(child);
         }
         this. = .prefixLength(this.);
     }

    
Creates a new File instance from a parent abstract pathname and a child pathname string.

If parent is null then the new File instance is created as if by invoking the single-argument File constructor on the given child pathname string.

Otherwise the parent abstract pathname is taken to denote a directory, and the child pathname string is taken to denote either a directory or a file. If the child pathname string is absolute then it is converted into a relative pathname in a system-dependent way. If parent is the empty abstract pathname then the new File instance is created by converting child into an abstract pathname and resolving the result against a system-dependent default directory. Otherwise each pathname string is converted into an abstract pathname and the child abstract pathname is resolved against the parent.

Parameters:
parent The parent abstract pathname
child The child pathname string
Throws:
java.lang.NullPointerException If child is null
 
     public File(File parentString child) {
         if (child == null) {
             throw new NullPointerException();
         }
         if (parent != null) {
             if (parent.path.equals("")) {
                 this. = .resolve(.getDefaultParent(),
                                        .normalize(child));
             } else {
                 this. = .resolve(parent.path,
                                        .normalize(child));
             }
         } else {
             this. = .normalize(child);
         }
         this. = .prefixLength(this.);
     }

    
Creates a new File instance by converting the given file: URI into an abstract pathname.

The exact form of a file: URI is system-dependent, hence the transformation performed by this constructor is also system-dependent.

For a given abstract pathname f it is guaranteed that

new File( f.toURI()).equals( f.getAbsoluteFile())
so long as the original abstract pathname, the URI, and the new abstract pathname are all created in (possibly different invocations of) the same Java virtual machine. This relationship typically does not hold, however, when a file: URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system.

Parameters:
uri An absolute, hierarchical URI with a scheme equal to "file", a non-empty path component, and undefined authority, query, and fragment components
Throws:
java.lang.NullPointerException If uri is null
java.lang.IllegalArgumentException If the preconditions on the parameter do not hold
Since:
1.4
See also:
toURI()
java.net.URI
 
     public File(URI uri) {
 
         // Check our many preconditions
         if (!uri.isAbsolute())
             throw new IllegalArgumentException("URI is not absolute");
         if (uri.isOpaque())
             throw new IllegalArgumentException("URI is not hierarchical");
         String scheme = uri.getScheme();
         if ((scheme == null) || !scheme.equalsIgnoreCase("file"))
             throw new IllegalArgumentException("URI scheme is not \"file\"");
         if (uri.getAuthority() != null)
             throw new IllegalArgumentException("URI has an authority component");
         if (uri.getFragment() != null)
             throw new IllegalArgumentException("URI has a fragment component");
         if (uri.getQuery() != null)
             throw new IllegalArgumentException("URI has a query component");
         String p = uri.getPath();
         if (p.equals(""))
             throw new IllegalArgumentException("URI path component is empty");
 
         // Okay, now initialize
         p = .fromURIPath(p);
         if (. != '/')
             p = p.replace('/'.);
         this. = .normalize(p);
         this. = .prefixLength(this.);
     }
 
 
     /* -- Path-component accessors -- */

    
Returns the name of the file or directory denoted by this abstract pathname. This is just the last name in the pathname's name sequence. If the pathname's name sequence is empty, then the empty string is returned.

Returns:
The name of the file or directory denoted by this abstract pathname, or the empty string if this pathname's name sequence is empty
 
     public String getName() {
         int index = .lastIndexOf();
         if (index < return .substring();
         return .substring(index + 1);
     }

    
Returns the pathname string of this abstract pathname's parent, or null if this pathname does not name a parent directory.

The parent of an abstract pathname consists of the pathname's prefix, if any, and each name in the pathname's name sequence except for the last. If the name sequence is empty then the pathname does not name a parent directory.

Returns:
The pathname string of the parent directory named by this abstract pathname, or null if this pathname does not name a parent
 
     public String getParent() {
         int index = .lastIndexOf();
         if (index < ) {
             if (( > 0) && (.length() > ))
                 return .substring(0, );
             return null;
         }
         return .substring(0, index);
     }

    
Returns the abstract pathname of this abstract pathname's parent, or null if this pathname does not name a parent directory.

The parent of an abstract pathname consists of the pathname's prefix, if any, and each name in the pathname's name sequence except for the last. If the name sequence is empty then the pathname does not name a parent directory.

Returns:
The abstract pathname of the parent directory named by this abstract pathname, or null if this pathname does not name a parent
Since:
1.2
 
     public File getParentFile() {
         String p = this.getParent();
         if (p == nullreturn null;
         return new File(pthis.);
     }

    
Converts this abstract pathname into a pathname string. The resulting string uses the default name-separator character to separate the names in the name sequence.

Returns:
The string form of this abstract pathname
 
     public String getPath() {
         return ;
     }
 
 
     /* -- Path operations -- */

    
Tests whether this abstract pathname is absolute. The definition of absolute pathname is system dependent. On UNIX systems, a pathname is absolute if its prefix is "/". On Microsoft Windows systems, a pathname is absolute if its prefix is a drive specifier followed by "\\", or if its prefix is "\\\\".

Returns:
true if this abstract pathname is absolute, false otherwise
 
     public boolean isAbsolute() {
         return .isAbsolute(this);
     }

    
Returns the absolute pathname string of this abstract pathname.

If this abstract pathname is already absolute, then the pathname string is simply returned as if by the getPath() method. If this abstract pathname is the empty abstract pathname then the pathname string of the current user directory, which is named by the system property user.dir, is returned. Otherwise this pathname is resolved in a system-dependent way. On UNIX systems, a relative pathname is made absolute by resolving it against the current user directory. On Microsoft Windows systems, a relative pathname is made absolute by resolving it against the current directory of the drive named by the pathname, if any; if not, it is resolved against the current user directory.

Returns:
The absolute pathname string denoting the same file or directory as this abstract pathname
Throws:
java.lang.SecurityException If a required system property value cannot be accessed.
See also:
isAbsolute()
 
     public String getAbsolutePath() {
         return .resolve(this);
     }

    
Returns the absolute form of this abstract pathname. Equivalent to new File(this.getAbsolutePath()).

Returns:
The absolute abstract pathname denoting the same file or directory as this abstract pathname
Throws:
java.lang.SecurityException If a required system property value cannot be accessed.
Since:
1.2
 
     public File getAbsoluteFile() {
         String absPath = getAbsolutePath();
         return new File(absPath.prefixLength(absPath));
     }

    
Returns the canonical pathname string of this abstract pathname.

A canonical pathname is both absolute and unique. The precise definition of canonical form is system-dependent. This method first converts this pathname to absolute form if necessary, as if by invoking the getAbsolutePath() method, and then maps it to its unique form in a system-dependent way. This typically involves removing redundant names such as "." and ".." from the pathname, resolving symbolic links (on UNIX platforms), and converting drive letters to a standard case (on Microsoft Windows platforms).

Every pathname that denotes an existing file or directory has a unique canonical form. Every pathname that denotes a nonexistent file or directory also has a unique canonical form. The canonical form of the pathname of a nonexistent file or directory may be different from the canonical form of the same pathname after the file or directory is created. Similarly, the canonical form of the pathname of an existing file or directory may be different from the canonical form of the same pathname after the file or directory is deleted.

Returns:
The canonical pathname string denoting the same file or directory as this abstract pathname
Throws:
IOException If an I/O error occurs, which is possible because the construction of the canonical pathname may require filesystem queries
java.lang.SecurityException If a required system property value cannot be accessed, or if a security manager exists and its java.lang.SecurityManager.checkRead(java.io.FileDescriptor) method denies read access to the file
Since:
JDK1.1
See also:
java.nio.file.Path.toRealPath(java.nio.file.LinkOption[])
 
     public String getCanonicalPath() throws IOException {
         if (isInvalid()) {
             throw new IOException("Invalid file path");
         }
         return .canonicalize(.resolve(this));
     }

    
Returns the canonical form of this abstract pathname. Equivalent to new File(this.getCanonicalPath()).

Returns:
The canonical pathname string denoting the same file or directory as this abstract pathname
Throws:
IOException If an I/O error occurs, which is possible because the construction of the canonical pathname may require filesystem queries
java.lang.SecurityException If a required system property value cannot be accessed, or if a security manager exists and its java.lang.SecurityManager.checkRead(java.io.FileDescriptor) method denies read access to the file
Since:
1.2
See also:
java.nio.file.Path.toRealPath(java.nio.file.LinkOption[])
 
     public File getCanonicalFile() throws IOException {
         String canonPath = getCanonicalPath();
         return new File(canonPath.prefixLength(canonPath));
     }
 
     private static String slashify(String pathboolean isDirectory) {
         String p = path;
         if (. != '/')
             p = p.replace(.'/');
         if (!p.startsWith("/"))
             p = "/" + p;
         if (!p.endsWith("/") && isDirectory)
             p = p + "/";
         return p;
     }

    
Converts this abstract pathname into a file: URL. The exact form of the URL is system-dependent. If it can be determined that the file denoted by this abstract pathname is a directory, then the resulting URL will end with a slash.

Deprecated:
This method does not automatically escape characters that are illegal in URLs. It is recommended that new code convert an abstract pathname into a URL by first converting it into a URI, via the toURI method, and then converting the URI into a URL via the URI.toURL method.
Returns:
A URL object representing the equivalent file URL
Throws:
java.net.MalformedURLException If the path cannot be parsed as a URL
Since:
1.2
See also:
toURI()
java.net.URI
java.net.URI.toURL()
java.net.URL
 
     @Deprecated
     public URL toURL() throws MalformedURLException {
         if (isInvalid()) {
             throw new MalformedURLException("Invalid file path");
         }
         return new URL("file"""slashify(getAbsolutePath(), isDirectory()));
     }

    
Constructs a file: URI that represents this abstract pathname.

The exact form of the URI is system-dependent. If it can be determined that the file denoted by this abstract pathname is a directory, then the resulting URI will end with a slash.

For a given abstract pathname f, it is guaranteed that

new File( f.toURI()).equals( f.getAbsoluteFile())
so long as the original abstract pathname, the URI, and the new abstract pathname are all created in (possibly different invocations of) the same Java virtual machine. Due to the system-dependent nature of abstract pathnames, however, this relationship typically does not hold when a file: URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system.

Note that when this abstract pathname represents a UNC pathname then all components of the UNC (including the server name component) are encoded in the URI path. The authority component is undefined, meaning that it is represented as null. The java.nio.file.Path class defines the toUri method to encode the server name in the authority component of the resulting URI. The toPath method may be used to obtain a Path representing this abstract pathname.

Returns:
An absolute, hierarchical URI with a scheme equal to "file", a path representing this abstract pathname, and undefined authority, query, and fragment components
Throws:
java.lang.SecurityException If a required system property value cannot be accessed.
Since:
1.4
See also:
File(java.net.URI)
java.net.URI
java.net.URI.toURL()
 
     public URI toURI() {
         try {
             File f = getAbsoluteFile();
             String sp = slashify(f.getPath(), f.isDirectory());
             if (sp.startsWith("//"))
                 sp = "//" + sp;
             return new URI("file"nullspnull);
         } catch (URISyntaxException x) {
             throw new Error(x);         // Can't happen
         }
     }
 
 
     /* -- Attribute accessors -- */

    
Tests whether the application can read the file denoted by this abstract pathname.

Returns:
true if and only if the file specified by this abstract pathname exists and can be read by the application; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file
 
     public boolean canRead() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return false;
         }
         return .checkAccess(this.);
     }

    
Tests whether the application can modify the file denoted by this abstract pathname.

Returns:
true if and only if the file system actually contains a file denoted by this abstract pathname and the application is allowed to write to the file; false otherwise.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
 
     public boolean canWrite() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkWrite();
         }
         if (isInvalid()) {
             return false;
         }
         return .checkAccess(this.);
     }

    
Tests whether the file or directory denoted by this abstract pathname exists.

Returns:
true if and only if the file or directory denoted by this abstract pathname exists; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file or directory
 
     public boolean exists() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return false;
         }
         return ((.getBooleanAttributes(this) & .) != 0);
     }

    
Tests whether the file denoted by this abstract pathname is a directory.

Where it is required to distinguish an I/O exception from the case that the file is not a directory, or where several attributes of the same file are required at the same time, then the java.nio.file.Files#readAttributes(Path , Class , LinkOption[] ) method may be used.

Returns:
true if and only if the file denoted by this abstract pathname exists and is a directory; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file
 
     public boolean isDirectory() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return false;
         }
         return ((.getBooleanAttributes(this) & .)
                 != 0);
     }

    
Tests whether the file denoted by this abstract pathname is a normal file. A file is normal if it is not a directory and, in addition, satisfies other system-dependent criteria. Any non-directory file created by a Java application is guaranteed to be a normal file.

Where it is required to distinguish an I/O exception from the case that the file is not a normal file, or where several attributes of the same file are required at the same time, then the java.nio.file.Files#readAttributes(Path , Class , LinkOption[] ) method may be used.

Returns:
true if and only if the file denoted by this abstract pathname exists and is a normal file; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file
 
     public boolean isFile() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return false;
         }
         return ((.getBooleanAttributes(this) & .) != 0);
     }

    
Tests whether the file named by this abstract pathname is a hidden file. The exact definition of hidden is system-dependent. On UNIX systems, a file is considered to be hidden if its name begins with a period character ('.'). On Microsoft Windows systems, a file is considered to be hidden if it has been marked as such in the filesystem.

Returns:
true if and only if the file denoted by this abstract pathname is hidden according to the conventions of the underlying platform
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file
Since:
1.2
 
     public boolean isHidden() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return false;
         }
         return ((.getBooleanAttributes(this) & .) != 0);
     }

    
Returns the time that the file denoted by this abstract pathname was last modified.

Where it is required to distinguish an I/O exception from the case where 0L is returned, or where several attributes of the same file are required at the same time, or where the time of last access or the creation time are required, then the java.nio.file.Files#readAttributes(Path , Class , LinkOption[] ) method may be used.

Returns:
A long value representing the time the file was last modified, measured in milliseconds since the epoch (00:00:00 GMT, January 1, 1970), or 0L if the file does not exist or if an I/O error occurs
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file
 
     public long lastModified() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return 0L;
         }
         return .getLastModifiedTime(this);
     }

    
Returns the length of the file denoted by this abstract pathname. The return value is unspecified if this pathname denotes a directory.

Where it is required to distinguish an I/O exception from the case that 0L is returned, or where several attributes of the same file are required at the same time, then the java.nio.file.Files#readAttributes(Path , Class , LinkOption[] ) method may be used.

Returns:
The length, in bytes, of the file denoted by this abstract pathname, or 0L if the file does not exist. Some operating systems may return 0L for pathnames denoting system-dependent entities such as devices or pipes.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file
 
     public long length() {
         SecurityManager security = System.getSecurityManager();
         if (security != null) {
             security.checkRead();
         }
         if (isInvalid()) {
             return 0L;
         }
         return .getLength(this);
     }
 
 
     /* -- File operations -- */

    
Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file.

Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead.

Returns:
true if the named file does not exist and was successfully created; false if the named file already exists
Throws:
IOException If an I/O error occurred
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
Since:
1.2
 
    public boolean createNewFile() throws IOException {
        SecurityManager security = System.getSecurityManager();
        if (security != nullsecurity.checkWrite();
        if (isInvalid()) {
            throw new IOException("Invalid file path");
        }
        return .createFileExclusively();
    }

    
Deletes the file or directory denoted by this abstract pathname. If this pathname denotes a directory, then the directory must be empty in order to be deleted.

Note that the java.nio.file.Files class defines the java.nio.file.Files.delete(java.nio.file.Path) method to throw an IOException when a file cannot be deleted. This is useful for error reporting and to diagnose why a file cannot be deleted.

Returns:
true if and only if the file or directory is successfully deleted; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkDelete(java.lang.String) method denies delete access to the file
    public boolean delete() {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkDelete();
        }
        if (isInvalid()) {
            return false;
        }
        return .delete(this);
    }

    
Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates. Files (or directories) are deleted in the reverse order that they are registered. Invoking this method to delete a file or directory that is already registered for deletion has no effect. Deletion will be attempted only for normal termination of the virtual machine, as defined by the Java Language Specification.

Once deletion has been requested, it is not possible to cancel the request. This method should therefore be used with care.

Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead.

Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkDelete(java.lang.String) method denies delete access to the file
Since:
1.2
See also:
delete()
    public void deleteOnExit() {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkDelete();
        }
        if (isInvalid()) {
            return;
        }
        DeleteOnExitHook.add();
    }

    
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.

If this abstract pathname does not denote a directory, then this method returns null. Otherwise an array of strings is returned, one for each file or directory in the directory. Names denoting the directory itself and the directory's parent directory are not included in the result. Each string is a file name rather than a complete path.

There is no guarantee that the name strings in the resulting array will appear in any specific order; they are not, in particular, guaranteed to appear in alphabetical order.

Note that the java.nio.file.Files class defines the java.nio.file.Files.newDirectoryStream(java.nio.file.Path) method to open a directory and iterate over the names of the files in the directory. This may use less resources when working with very large directories, and may be more responsive when working with remote directories.

Returns:
An array of strings naming the files and directories in the directory denoted by this abstract pathname. The array will be empty if the directory is empty. Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the directory
    public String[] list() {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkRead();
        }
        if (isInvalid()) {
            return null;
        }
        return .list(this);
    }

    
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. The behavior of this method is the same as that of the list() method, except that the strings in the returned array must satisfy the filter. If the given filter is null then all names are accepted. Otherwise, a name satisfies the filter if and only if the value true results when the FilenameFilter.accept(java.io.File,java.lang.String) method of the filter is invoked on this abstract pathname and the name of a file or directory in the directory that it denotes.

Parameters:
filter A filename filter
Returns:
An array of strings naming the files and directories in the directory denoted by this abstract pathname that were accepted by the given filter. The array will be empty if the directory is empty or if no names were accepted by the filter. Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the directory
See also:
java.nio.file.Files.newDirectoryStream(java.nio.file.Path,java.lang.String)
    public String[] list(FilenameFilter filter) {
        String names[] = list();
        if ((names == null) || (filter == null)) {
            return names;
        }
        List<Stringv = new ArrayList<>();
        for (int i = 0 ; i < names.length ; i++) {
            if (filter.accept(thisnames[i])) {
                v.add(names[i]);
            }
        }
        return v.toArray(new String[v.size()]);
    }

    
Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.

If this abstract pathname does not denote a directory, then this method returns null. Otherwise an array of File objects is returned, one for each file or directory in the directory. Pathnames denoting the directory itself and the directory's parent directory are not included in the result. Each resulting abstract pathname is constructed from this abstract pathname using the File(File, String) constructor. Therefore if this pathname is absolute then each resulting pathname is absolute; if this pathname is relative then each resulting pathname will be relative to the same directory.

There is no guarantee that the name strings in the resulting array will appear in any specific order; they are not, in particular, guaranteed to appear in alphabetical order.

Note that the java.nio.file.Files class defines the java.nio.file.Files.newDirectoryStream(java.nio.file.Path) method to open a directory and iterate over the names of the files in the directory. This may use less resources when working with very large directories.

Returns:
An array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname. The array will be empty if the directory is empty. Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the directory
Since:
1.2
    public File[] listFiles() {
        String[] ss = list();
        if (ss == nullreturn null;
        int n = ss.length;
        File[] fs = new File[n];
        for (int i = 0; i < ni++) {
            fs[i] = new File(ss[i], this);
        }
        return fs;
    }

    
Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. The behavior of this method is the same as that of the listFiles() method, except that the pathnames in the returned array must satisfy the filter. If the given filter is null then all pathnames are accepted. Otherwise, a pathname satisfies the filter if and only if the value true results when the FilenameFilter.accept(File, String) method of the filter is invoked on this abstract pathname and the name of a file or directory in the directory that it denotes.

Parameters:
filter A filename filter
Returns:
An array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname. The array will be empty if the directory is empty. Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the directory
Since:
1.2
See also:
java.nio.file.Files.newDirectoryStream(java.nio.file.Path,java.lang.String)
    public File[] listFiles(FilenameFilter filter) {
        String ss[] = list();
        if (ss == nullreturn null;
        ArrayList<Filefiles = new ArrayList<>();
        for (String s : ss)
            if ((filter == null) || filter.accept(thiss))
                files.add(new File(sthis));
        return files.toArray(new File[files.size()]);
    }

    
Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. The behavior of this method is the same as that of the listFiles() method, except that the pathnames in the returned array must satisfy the filter. If the given filter is null then all pathnames are accepted. Otherwise, a pathname satisfies the filter if and only if the value true results when the FileFilter.accept(File) method of the filter is invoked on the pathname.

Parameters:
filter A file filter
Returns:
An array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname. The array will be empty if the directory is empty. Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the directory
Since:
1.2
See also:
java.nio.file.Files.newDirectoryStream(java.nio.file.Path,java.nio.file.DirectoryStream.Filter)
    public File[] listFiles(FileFilter filter) {
        String ss[] = list();
        if (ss == nullreturn null;
        ArrayList<Filefiles = new ArrayList<>();
        for (String s : ss) {
            File f = new File(sthis);
            if ((filter == null) || filter.accept(f))
                files.add(f);
        }
        return files.toArray(new File[files.size()]);
    }

    
Creates the directory named by this abstract pathname.

Returns:
true if and only if the directory was created; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method does not permit the named directory to be created
    public boolean mkdir() {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
        }
        if (isInvalid()) {
            return false;
        }
        return .createDirectory(this);
    }

    
Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories. Note that if this operation fails it may have succeeded in creating some of the necessary parent directories.

Returns:
true if and only if the directory was created, along with all necessary parent directories; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method does not permit verification of the existence of the named directory and all necessary parent directories; or if the java.lang.SecurityManager.checkWrite(java.lang.String) method does not permit the named directory and all necessary parent directories to be created
    public boolean mkdirs() {
        if (exists()) {
            return false;
        }
        if (mkdir()) {
            return true;
        }
        File canonFile = null;
        try {
            canonFile = getCanonicalFile();
        } catch (IOException e) {
            return false;
        }
        File parent = canonFile.getParentFile();
        return (parent != null && (parent.mkdirs() || parent.exists()) &&
                canonFile.mkdir());
    }

    
Renames the file denoted by this abstract pathname.

Many aspects of the behavior of this method are inherently platform-dependent: The rename operation might not be able to move a file from one filesystem to another, it might not be atomic, and it might not succeed if a file with the destination abstract pathname already exists. The return value should always be checked to make sure that the rename operation was successful.

Note that the java.nio.file.Files class defines the java.nio.file.Files.move(java.nio.file.Path,java.nio.file.Path,java.nio.file.CopyOption[]) method to move or rename a file in a platform independent manner.

Parameters:
dest The new abstract pathname for the named file
Returns:
true if and only if the renaming succeeded; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to either the old or new pathnames
java.lang.NullPointerException If parameter dest is null
    public boolean renameTo(File dest) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
            security.checkWrite(dest.path);
        }
        if (dest == null) {
            throw new NullPointerException();
        }
        if (this.isInvalid() || dest.isInvalid()) {
            return false;
        }
        return .rename(thisdest);
    }

    
Sets the last-modified time of the file or directory named by this abstract pathname.

All platforms support file-modification times to the nearest second, but some provide more precision. The argument will be truncated to fit the supported precision. If the operation succeeds and no intervening operations on the file take place, then the next invocation of the lastModified() method will return the (possibly truncated) time argument that was passed to this method.

Parameters:
time The new last-modified time, measured in milliseconds since the epoch (00:00:00 GMT, January 1, 1970)
Returns:
true if and only if the operation succeeded; false otherwise
Throws:
java.lang.IllegalArgumentException If the argument is negative
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the named file
Since:
1.2
    public boolean setLastModified(long time) {
        if (time < 0) throw new IllegalArgumentException("Negative time");
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
        }
        if (isInvalid()) {
            return false;
        }
        return .setLastModifiedTime(thistime);
    }

    
Marks the file or directory named by this abstract pathname so that only read operations are allowed. After invoking this method the file or directory is guaranteed not to change until it is either deleted or marked to allow write access. Whether or not a read-only file or directory may be deleted depends upon the underlying system.

Returns:
true if and only if the operation succeeded; false otherwise
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the named file
Since:
1.2
    public boolean setReadOnly() {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
        }
        if (isInvalid()) {
            return false;
        }
        return .setReadOnly(this);
    }

    
Sets the owner's or everybody's write permission for this abstract pathname.

The java.nio.file.Files class defines methods that operate on file attributes including file permissions. This may be used when finer manipulation of file permissions is required.

Parameters:
writable If true, sets the access permission to allow write operations; if false to disallow write operations
ownerOnly If true, the write permission applies only to the owner's write permission; otherwise, it applies to everybody. If the underlying file system can not distinguish the owner's write permission from that of others, then the permission will apply to everybody, regardless of this value.
Returns:
true if and only if the operation succeeded. The operation will fail if the user does not have permission to change the access permissions of this abstract pathname.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the named file
Since:
1.6
    public boolean setWritable(boolean writableboolean ownerOnly) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
        }
        if (isInvalid()) {
            return false;
        }
        return .setPermission(this.writableownerOnly);
    }

    
A convenience method to set the owner's write permission for this abstract pathname.

An invocation of this method of the form file.setWritable(arg) behaves in exactly the same way as the invocation

     file.setWritable(arg, true) 

Parameters:
writable If true, sets the access permission to allow write operations; if false to disallow write operations
Returns:
true if and only if the operation succeeded. The operation will fail if the user does not have permission to change the access permissions of this abstract pathname.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
Since:
1.6
    public boolean setWritable(boolean writable) {
        return setWritable(writabletrue);
    }

    
Sets the owner's or everybody's read permission for this abstract pathname.

The java.nio.file.Files class defines methods that operate on file attributes including file permissions. This may be used when finer manipulation of file permissions is required.

Parameters:
readable If true, sets the access permission to allow read operations; if false to disallow read operations
ownerOnly If true, the read permission applies only to the owner's read permission; otherwise, it applies to everybody. If the underlying file system can not distinguish the owner's read permission from that of others, then the permission will apply to everybody, regardless of this value.
Returns:
true if and only if the operation succeeded. The operation will fail if the user does not have permission to change the access permissions of this abstract pathname. If readable is false and the underlying file system does not implement a read permission, then the operation will fail.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
Since:
1.6
    public boolean setReadable(boolean readableboolean ownerOnly) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
        }
        if (isInvalid()) {
            return false;
        }
        return .setPermission(this.readableownerOnly);
    }

    
A convenience method to set the owner's read permission for this abstract pathname.

An invocation of this method of the form file.setReadable(arg) behaves in exactly the same way as the invocation

     file.setReadable(arg, true) 

Parameters:
readable If true, sets the access permission to allow read operations; if false to disallow read operations
Returns:
true if and only if the operation succeeded. The operation will fail if the user does not have permission to change the access permissions of this abstract pathname. If readable is false and the underlying file system does not implement a read permission, then the operation will fail.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
Since:
1.6
    public boolean setReadable(boolean readable) {
        return setReadable(readabletrue);
    }

    
Sets the owner's or everybody's execute permission for this abstract pathname.

The java.nio.file.Files class defines methods that operate on file attributes including file permissions. This may be used when finer manipulation of file permissions is required.

Parameters:
executable If true, sets the access permission to allow execute operations; if false to disallow execute operations
ownerOnly If true, the execute permission applies only to the owner's execute permission; otherwise, it applies to everybody. If the underlying file system can not distinguish the owner's execute permission from that of others, then the permission will apply to everybody, regardless of this value.
Returns:
true if and only if the operation succeeded. The operation will fail if the user does not have permission to change the access permissions of this abstract pathname. If executable is false and the underlying file system does not implement an execute permission, then the operation will fail.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
Since:
1.6
    public boolean setExecutable(boolean executableboolean ownerOnly) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkWrite();
        }
        if (isInvalid()) {
            return false;
        }
        return .setPermission(this.executableownerOnly);
    }

    
A convenience method to set the owner's execute permission for this abstract pathname.

An invocation of this method of the form file.setExcutable(arg) behaves in exactly the same way as the invocation

     file.setExecutable(arg, true) 

Parameters:
executable If true, sets the access permission to allow execute operations; if false to disallow execute operations
Returns:
true if and only if the operation succeeded. The operation will fail if the user does not have permission to change the access permissions of this abstract pathname. If executable is false and the underlying file system does not implement an excute permission, then the operation will fail.
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method denies write access to the file
Since:
1.6
    public boolean setExecutable(boolean executable) {
        return setExecutable(executabletrue);
    }

    
Tests whether the application can execute the file denoted by this abstract pathname.

Returns:
true if and only if the abstract pathname exists and the application is allowed to execute the file
Throws:
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkExec(java.lang.String) method denies execute access to the file
Since:
1.6
    public boolean canExecute() {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkExec();
        }
        if (isInvalid()) {
            return false;
        }
        return .checkAccess(this.);
    }
    /* -- Filesystem interface -- */

    
List the available filesystem roots.

A particular Java platform may support zero or more hierarchically-organized file systems. Each file system has a root directory from which all other files in that file system can be reached. Windows platforms, for example, have a root directory for each active drive; UNIX platforms have a single root directory, namely "/". The set of available filesystem roots is affected by various system-level operations such as the insertion or ejection of removable media and the disconnecting or unmounting of physical or virtual disk drives.

This method returns an array of File objects that denote the root directories of the available filesystem roots. It is guaranteed that the canonical pathname of any file physically present on the local machine will begin with one of the roots returned by this method.

The canonical pathname of a file that resides on some other machine and is accessed via a remote-filesystem protocol such as SMB or NFS may or may not begin with one of the roots returned by this method. If the pathname of a remote file is syntactically indistinguishable from the pathname of a local file then it will begin with one of the roots returned by this method. Thus, for example, File objects denoting the root directories of the mapped network drives of a Windows platform will be returned by this method, while File objects containing UNC pathnames will not be returned by this method.

Unlike most methods in this class, this method does not throw security exceptions. If a security manager exists and its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to a particular root directory, then that directory will not appear in the result.

Returns:
An array of File objects denoting the available filesystem roots, or null if the set of roots could not be determined. The array will be empty if there are no filesystem roots.
Since:
1.2
See also:
java.nio.file.FileStore
    public static File[] listRoots() {
        return .listRoots();
    }
    /* -- Disk usage -- */

    
Returns the size of the partition named by this abstract pathname.

Returns:
The size, in bytes, of the partition or 0L if this abstract pathname does not name a partition
Throws:
java.lang.SecurityException If a security manager has been installed and it denies java.lang.RuntimePermission("getFileSystemAttributes") or its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file named by this abstract pathname
Since:
1.6
    public long getTotalSpace() {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
            sm.checkRead();
        }
        if (isInvalid()) {
            return 0L;
        }
        return .getSpace(this.);
    }

    
Returns the number of unallocated bytes in the partition named by this abstract path name.

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 this call. It is likely to be made inaccurate by any external I/O operations including those made on the system outside of this virtual machine. This method makes no guarantee that write operations to this file system will succeed.

Returns:
The number of unallocated bytes on the partition or 0L if the abstract pathname does not name a partition. This value will be less than or equal to the total file system size returned by getTotalSpace().
Throws:
java.lang.SecurityException If a security manager has been installed and it denies java.lang.RuntimePermission("getFileSystemAttributes") or its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file named by this abstract pathname
Since:
1.6
    public long getFreeSpace() {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
            sm.checkRead();
        }
        if (isInvalid()) {
            return 0L;
        }
        return .getSpace(this.);
    }

    
Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname. When possible, this method checks for write permissions and other operating system restrictions and will therefore usually provide a more accurate estimate of how much new data can actually be written than getFreeSpace().

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 unallocated bytes is most likely to be accurate immediately after this call. It is likely to be made inaccurate by any external I/O operations including those made on the system outside of this virtual machine. This method makes no guarantee that write operations to this file system will succeed.

Returns:
The number of available bytes on the partition or 0L if the abstract pathname does not name a partition. On systems where this information is not available, this method will be equivalent to a call to getFreeSpace().
Throws:
java.lang.SecurityException If a security manager has been installed and it denies java.lang.RuntimePermission("getFileSystemAttributes") or its java.lang.SecurityManager.checkRead(java.lang.String) method denies read access to the file named by this abstract pathname
Since:
1.6
    public long getUsableSpace() {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
            sm.checkRead();
        }
        if (isInvalid()) {
            return 0L;
        }
        return .getSpace(this.);
    }
    /* -- Temporary files -- */
    private static class TempDirectory {
        private TempDirectory() { }
        // temporary directory location
        private static final File tmpdir = new File(AccessController
            .doPrivileged(new GetPropertyAction("java.io.tmpdir")));
        static File location() {
            return ;
        }
        // file name generation
        private static final SecureRandom random = new SecureRandom();
        static File generateFile(String prefixString suffixFile dir)
            throws IOException
        {
            long n = .nextLong();
            if (n == .) {
                n = 0;      // corner case
            } else {
                n = Math.abs(n);
            }
            String name = prefix + Long.toString(n) + suffix;
            File f = new File(dirname);
            if (!name.equals(f.getName()))
                throw new IOException("Unable to create temporary file");
            return f;
        }
    }

    

Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name. If this method returns successfully then it is guaranteed that:

  1. The file denoted by the returned abstract pathname did not exist before this method was invoked, and
  2. Neither this method nor any of its variants will return the same abstract pathname again in the current invocation of the virtual machine.
This method provides only part of a temporary-file facility. To arrange for a file created by this method to be deleted automatically, use the deleteOnExit() method.

The prefix argument must be at least three characters long. It is recommended that the prefix be a short, meaningful string such as "hjb" or "mail". The suffix argument may be null, in which case the suffix ".tmp" will be used.

To create the new file, the prefix and the suffix may first be adjusted to fit the limitations of the underlying platform. If the prefix is too long then it will be truncated, but its first three characters will always be preserved. If the suffix is too long then it too will be truncated, but if it begins with a period character ('.') then the period and the first three characters following it will always be preserved. Once these adjustments have been made the name of the new file will be generated by concatenating the prefix, five or more internally-generated characters, and the suffix.

If the directory argument is null then the system-dependent default temporary-file directory will be used. The default temporary-file directory is specified by the system property java.io.tmpdir. On UNIX systems the default value of this property is typically "/tmp" or "/var/tmp"; on Microsoft Windows systems it is typically "C:\\WINNT\\TEMP". A different value may be given to this system property when the Java virtual machine is invoked, but programmatic changes to this property are not guaranteed to have any effect upon the temporary directory used by this method.

Parameters:
prefix The prefix string to be used in generating the file's name; must be at least three characters long
suffix The suffix string to be used in generating the file's name; may be null, in which case the suffix ".tmp" will be used
directory The directory in which the file is to be created, or null if the default temporary-file directory is to be used
Returns:
An abstract pathname denoting a newly-created empty file
Throws:
java.lang.IllegalArgumentException If the prefix argument contains fewer than three characters
IOException If a file could not be created
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method does not allow a file to be created
Since:
1.2
    public static File createTempFile(String prefixString suffix,
                                      File directory)
        throws IOException
    {
        if (prefix.length() < 3)
            throw new IllegalArgumentException("Prefix string too short");
        if (suffix == null)
            suffix = ".tmp";
        File tmpdir = (directory != null) ? directory
                                          : TempDirectory.location();
        File f;
        try {
            do {
                f = TempDirectory.generateFile(prefixsuffixtmpdir);
            } while (f.exists());
            if (!f.createNewFile())
                throw new IOException("Unable to create temporary file");
        } catch (SecurityException se) {
            // don't reveal temporary directory location
            if (directory == null)
                throw new SecurityException("Unable to create temporary file");
            throw se;
        }
        return f;
    }

    
Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name. Invoking this method is equivalent to invoking createTempFile(prefix, suffix, null).

The java.nio.file.Files.createTempFile(java.lang.String,java.lang.String,java.nio.file.attribute.FileAttribute[]) method provides an alternative method to create an empty file in the temporary-file directory. Files created by that method may have more restrictive access permissions to files created by this method and so may be more suited to security-sensitive applications.

Parameters:
prefix The prefix string to be used in generating the file's name; must be at least three characters long
suffix The suffix string to be used in generating the file's name; may be null, in which case the suffix ".tmp" will be used
Returns:
An abstract pathname denoting a newly-created empty file
Throws:
java.lang.IllegalArgumentException If the prefix argument contains fewer than three characters
IOException If a file could not be created
java.lang.SecurityException If a security manager exists and its java.lang.SecurityManager.checkWrite(java.lang.String) method does not allow a file to be created
Since:
1.2
See also:
java.nio.file.Files#createTempDirectory(String , FileAttribute[] )
    public static File createTempFile(String prefixString suffix)
        throws IOException
    {
        return createTempFile(prefixsuffixnull);
    }
    /* -- Basic infrastructure -- */

    
Compares two abstract pathnames lexicographically. The ordering defined by this method depends upon the underlying system. On UNIX systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows systems it is not.

Parameters:
pathname The abstract pathname to be compared to this abstract pathname
Returns:
Zero if the argument is equal to this abstract pathname, a value less than zero if this abstract pathname is lexicographically less than the argument, or a value greater than zero if this abstract pathname is lexicographically greater than the argument
Since:
1.2
    public int compareTo(File pathname) {
        return .compare(thispathname);
    }

    
Tests this abstract pathname for equality with the given object. Returns true if and only if the argument is not null and is an abstract pathname that denotes the same file or directory as this abstract pathname. Whether or not two abstract pathnames are equal depends upon the underlying system. On UNIX systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows systems it is not.

Parameters:
obj The object to be compared with this abstract pathname
Returns:
true if and only if the objects are the same; false otherwise
    public boolean equals(Object obj) {
        if ((obj != null) && (obj instanceof File)) {
            return compareTo((File)obj) == 0;
        }
        return false;
    }

    
Computes a hash code for this abstract pathname. Because equality of abstract pathnames is inherently system-dependent, so is the computation of their hash codes. On UNIX systems, the hash code of an abstract pathname is equal to the exclusive or of the hash code of its pathname string and the decimal value 1234321. On Microsoft Windows systems, the hash code is equal to the exclusive or of the hash code of its pathname string converted to lower case and the decimal value 1234321. Locale is not taken into account on lowercasing the pathname string.

Returns:
A hash code for this abstract pathname
    public int hashCode() {
        return .hashCode(this);
    }

    
Returns the pathname string of this abstract pathname. This is just the string returned by the getPath() method.

Returns:
The string form of this abstract pathname
    public String toString() {
        return getPath();
    }

    
WriteObject is called to save this filename. The separator character is saved also so it can be replaced in case the path is reconstituted on a different host type.

SerialData:
Default fields followed by separator character.
    private synchronized void writeObject(java.io.ObjectOutputStream s)
        throws IOException
    {
        s.defaultWriteObject();
        s.writeChar(this.); // Add the separator character
    }

    
readObject is called to restore this filename. The original separator character is read. If it is different than the separator character on this system, then the old separator is replaced by the local separator.
    private synchronized void readObject(java.io.ObjectInputStream s)
         throws IOExceptionClassNotFoundException
    {
        ObjectInputStream.GetField fields = s.readFields();
        String pathField = (String)fields.get("path"null);
        char sep = s.readChar(); // read the previous separator char
        if (sep != )
            pathField = pathField.replace(sep);
        this. = .normalize(pathField);
        this. = .prefixLength(this.);
    }

    
use serialVersionUID from JDK 1.0.2 for interoperability
    private static final long serialVersionUID = 301077366599181567L;
    // -- Integration with java.nio.file --
    private volatile transient Path filePath;

    
Returns a java.nio.file.Path object constructed from the this abstract path. The resulting Path is associated with the default-filesystem.

The first invocation of this method works as if invoking it were equivalent to evaluating the expression:

 FileSystems.getDefault().java.nio.file.FileSystem.getPath(java.lang.String,java.lang.String[])(this.getPath());
 
Subsequent invocations of this method return the same Path.

If this abstract pathname is the empty abstract pathname then this method returns a Path that may be used to access the current user directory.

Returns:
a Path constructed from this abstract path
Throws:
java.nio.file.InvalidPathException if a Path object cannot be constructed from the abstract path (see FileSystem.getPath)
Since:
1.7
See also:
java.nio.file.Path.toFile()
    public Path toPath() {
        Path result = ;
        if (result == null) {
            synchronized (this) {
                result = ;
                if (result == null) {
                    result = FileSystems.getDefault().getPath();
                     = result;
                }
            }
        }
        return result;
    }
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