Files (Guava: Google Core Libraries for Java 27.1-jre API)

java.lang.Object
- com.google.common.io.Files

```
@GwtIncompatible
public final class Files
extends Object
```
Provides utility methods for working with files.
Path users will find similar utilities in MoreFiles and the JDK's Files class.

Since:

1.0

Author:

Chris Nokleberg, Colin Decker

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static void`	`append(CharSequence from, File to, Charset charset)` Deprecated. Prefer `asCharSink(to, charset, FileWriteMode.APPEND).write(from)`. This method is scheduled to be removed in January 2019.
`static ByteSink`	`asByteSink(File file, FileWriteMode... modes)` Returns a new `ByteSink` for writing bytes to the given file.
`static ByteSource`	`asByteSource(File file)` Returns a new `ByteSource` for reading bytes from the given file.
`static CharSink`	`asCharSink(File file, Charset charset, FileWriteMode... modes)` Returns a new `CharSink` for writing character data to the given file using the given character set.
`static CharSource`	`asCharSource(File file, Charset charset)` Returns a new `CharSource` for reading character data from the given file using the given character set.
`static void`	`copy(File from, Charset charset, Appendable to)` Deprecated. Prefer `asCharSource(from, charset).copyTo(to)`. This method is scheduled to be removed in January 2019.
`static void`	`copy(File from, File to)` Copies all the bytes from one file to another.
`static void`	`copy(File from, OutputStream to)` Copies all bytes from a file to an output stream.
`static void`	`createParentDirs(File file)` Creates any necessary but nonexistent parent directories of the specified file.
`static File`	`createTempDir()` Atomically creates a new directory somewhere beneath the system's temporary directory (as defined by the `java.io.tmpdir` system property), and returns its name.
`static boolean`	`equal(File file1, File file2)` Returns true if the given files exist, are not directories, and contain the same bytes.
`static Traverser<File>`	`fileTraverser()` Returns a `Traverser` instance for the file and directory tree.
`static String`	`getFileExtension(String fullName)` Returns the file extension for the given file name, or the empty string if the file has no extension.
`static String`	`getNameWithoutExtension(String file)` Returns the file name without its file extension or path.
`static HashCode`	`hash(File file, HashFunction hashFunction)` Deprecated. Prefer `asByteSource(file).hash(hashFunction)`. This method is scheduled to be removed in January 2019.
`static Predicate<File>`	`isDirectory()` Returns a predicate that returns the result of `File.isDirectory()` on input files.
`static Predicate<File>`	`isFile()` Returns a predicate that returns the result of `File.isFile()` on input files.
`static MappedByteBuffer`	`map(File file)` Fully maps a file read-only in to memory as per `FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long)`.
`static MappedByteBuffer`	`map(File file, FileChannel.MapMode mode)` Fully maps a file in to memory as per `FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long)` using the requested `FileChannel.MapMode`.
`static MappedByteBuffer`	`map(File file, FileChannel.MapMode mode, long size)` Maps a file in to memory as per `FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long)` using the requested `FileChannel.MapMode`.
`static void`	`move(File from, File to)` Moves a file from one path to another.
`static BufferedReader`	`newReader(File file, Charset charset)` Returns a buffered reader that reads from a file using the given character set.
`static BufferedWriter`	`newWriter(File file, Charset charset)` Returns a buffered writer that writes to a file using the given character set.
`static <T> T`	`readBytes(File file, ByteProcessor<T> processor)` Deprecated. Prefer `asByteSource(file).read(processor)`. This method is scheduled to be removed in January 2019.
`static String`	`readFirstLine(File file, Charset charset)` Deprecated. Prefer `asCharSource(file, charset).readFirstLine()`. This method is scheduled to be removed in January 2019.
`static List<String>`	`readLines(File file, Charset charset)` Reads all of the lines from a file.
`static <T> T`	`readLines(File file, Charset charset, LineProcessor<T> callback)` Deprecated. Prefer `asCharSource(file, charset).readLines(callback)`. This method is scheduled to be removed in January 2019.
`static String`	`simplifyPath(String pathname)` Returns the lexically cleaned form of the path name, usually (but not always) equivalent to the original.
`static byte[]`	`toByteArray(File file)` Reads all bytes from a file into a byte array.
`static String`	`toString(File file, Charset charset)` Deprecated. Prefer `asCharSource(file, charset).read()`. This method is scheduled to be removed in January 2019.
`static void`	`touch(File file)` Creates an empty file or updates the last updated timestamp on the same as the unix command of the same name.
`static void`	`write(byte[] from, File to)` Overwrites a file with the contents of a byte array.
`static void`	`write(CharSequence from, File to, Charset charset)` Deprecated. Prefer `asCharSink(to, charset).write(from)`. This method is scheduled to be removed in January 2019.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - newReader
```
@Beta
public static BufferedReader newReader(File file,
                                             Charset charset)
                                      throws FileNotFoundException
```
    Returns a buffered reader that reads from a file using the given character set.
    Path equivalent: Files.newBufferedReader(java.nio.file.Path, Charset).
    
    Parameters:
    
    file - the file to read from
    
    charset - the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
    
    Returns:
    
    the buffered reader
    
    Throws:
    
    FileNotFoundException
  - newWriter
```
@Beta
public static BufferedWriter newWriter(File file,
                                             Charset charset)
                                      throws FileNotFoundException
```
    Returns a buffered writer that writes to a file using the given character set.
    Path equivalent: Files.newBufferedWriter(java.nio.file.Path, Charset, java.nio.file.OpenOption...).
    
    Parameters:
    
    file - the file to write to
    
    charset - the charset used to encode the output stream; see StandardCharsets for helpful predefined constants
    
    Returns:
    
    the buffered writer
    
    Throws:
    
    FileNotFoundException
  - asByteSource
```
public static ByteSource asByteSource(File file)
```
    Returns a new ByteSource for reading bytes from the given file.
    
    Since:
    
    14.0
  - asByteSink
```
public static ByteSink asByteSink(File file,
                                  FileWriteMode... modes)
```
    Returns a new ByteSink for writing bytes to the given file. The given modes control how the file is opened for writing. When no mode is provided, the file will be truncated before writing. When the APPEND mode is provided, writes will append to the end of the file without truncating it.
    
    Since:
    
    14.0
  - asCharSource
```
public static CharSource asCharSource(File file,
                                      Charset charset)
```
    Returns a new CharSource for reading character data from the given file using the given character set.
    
    Since:
    
    14.0
  - asCharSink
```
public static CharSink asCharSink(File file,
                                  Charset charset,
                                  FileWriteMode... modes)
```
    Returns a new CharSink for writing character data to the given file using the given character set. The given modes control how the file is opened for writing. When no mode is provided, the file will be truncated before writing. When the APPEND mode is provided, writes will append to the end of the file without truncating it.
    
    Since:
    
    14.0
  - toByteArray
```
@Beta
public static byte[] toByteArray(File file)
                                throws IOException
```
    Reads all bytes from a file into a byte array.
    Path equivalent: Files.readAllBytes(java.nio.file.Path).
    
    Parameters:
    
    file - the file to read from
    
    Returns:
    
    a byte array containing all the bytes from file
    
    Throws:
    
    IllegalArgumentException - if the file is bigger than the largest possible byte array (2^31 - 1)
    
    IOException - if an I/O error occurs
  - toString
```
@Beta
 @Deprecated
public static String toString(File file,
                                                 Charset charset)
                                          throws IOException
```
    Deprecated. Prefer asCharSource(file, charset).read(). This method is scheduled to be removed in January 2019.
    
    Reads all characters from a file into a String, using the given character set.
    
    Parameters:
    
    file - the file to read from
    
    charset - the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
    
    Returns:
    
    a string containing all the characters from the file
    
    Throws:
    
    IOException - if an I/O error occurs
  - write
```
@Beta
public static void write(byte[] from,
                               File to)
                        throws IOException
```
    Overwrites a file with the contents of a byte array.
    Path equivalent: Files.write(java.nio.file.Path, byte[], java.nio.file.OpenOption...).
    
    Parameters:
    
    from - the bytes to write
    
    to - the destination file
    
    Throws:
    
    IOException - if an I/O error occurs
  - write
```
@Beta
 @Deprecated
public static void write(CharSequence from,
                                            File to,
                                            Charset charset)
                                     throws IOException
```
    Deprecated. Prefer asCharSink(to, charset).write(from). This method is scheduled to be removed in January 2019.
    
    Writes a character sequence (such as a string) to a file using the given character set.
    
    Parameters:
    
    from - the character sequence to write
    
    to - the destination file
    
    charset - the charset used to encode the output stream; see StandardCharsets for helpful predefined constants
    
    Throws:
    
    IOException - if an I/O error occurs
  - copy
```
@Beta
public static void copy(File from,
                              OutputStream to)
                       throws IOException
```
    Copies all bytes from a file to an output stream.
    Path equivalent: Files.copy(java.nio.file.Path, OutputStream).
    
    Parameters:
    
    from - the source file
    
    to - the output stream
    
    Throws:
    
    IOException - if an I/O error occurs
  - copy
```
@Beta
public static void copy(File from,
                              File to)
                       throws IOException
```
    Copies all the bytes from one file to another.
    Copying is not an atomic operation - in the case of an I/O error, power loss, process termination, or other problems, to may not be a complete copy of from. If you need to guard against those conditions, you should employ other file-level synchronization.
    Warning: If to represents an existing file, that file will be overwritten with the contents of from. If to and from refer to the same file, the contents of that file will be deleted.
    Path equivalent: Files.copy(java.nio.file.Path, java.nio.file.Path, java.nio.file.CopyOption...).
    
    Parameters:
    
    from - the source file
    
    to - the destination file
    
    Throws:
    
    IOException - if an I/O error occurs
    
    IllegalArgumentException - if from.equals(to)
  - copy
```
@Beta
 @Deprecated
public static void copy(File from,
                                           Charset charset,
                                           Appendable to)
                                    throws IOException
```
    Deprecated. Prefer asCharSource(from, charset).copyTo(to). This method is scheduled to be removed in January 2019.
    
    Copies all characters from a file to an appendable object, using the given character set.
    
    Parameters:
    
    from - the source file
    
    charset - the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
    
    to - the appendable object
    
    Throws:
    
    IOException - if an I/O error occurs
  - append
```
@Beta
 @Deprecated
public static void append(CharSequence from,
                                             File to,
                                             Charset charset)
                                      throws IOException
```
    Deprecated. Prefer asCharSink(to, charset, FileWriteMode.APPEND).write(from). This method is scheduled to be removed in January 2019.
    
    Appends a character sequence (such as a string) to a file using the given character set.
    
    Parameters:
    
    from - the character sequence to append
    
    to - the destination file
    
    charset - the charset used to encode the output stream; see StandardCharsets for helpful predefined constants
    
    Throws:
    
    IOException - if an I/O error occurs
  - equal
```
@Beta
public static boolean equal(File file1,
                                  File file2)
                           throws IOException
```
    Returns true if the given files exist, are not directories, and contain the same bytes.
    
    Throws:
    
    IOException - if an I/O error occurs
  - createTempDir
```
@Beta
public static File createTempDir()
```
    Atomically creates a new directory somewhere beneath the system's temporary directory (as defined by the java.io.tmpdir system property), and returns its name.
    Use this method instead of File.createTempFile(String, String) when you wish to create a directory, not a regular file. A common pitfall is to call createTempFile, delete the file and create a directory in its place, but this leads a race condition which can be exploited to create security vulnerabilities, especially when executable files are to be written into the directory.
    This method assumes that the temporary volume is writable, has free inodes and free blocks, and that it will not be called thousands of times per second.
    Path equivalent: Files.createTempDirectory(java.nio.file.Path, java.lang.String, java.nio.file.attribute.FileAttribute<?>...).
    
    Returns:
    
    the newly-created directory
    
    Throws:
    
    IllegalStateException - if the directory could not be created
  - touch
```
@Beta
public static void touch(File file)
                        throws IOException
```
    Creates an empty file or updates the last updated timestamp on the same as the unix command of the same name.
    
    Parameters:
    
    file - the file to create or update
    
    Throws:
    
    IOException - if an I/O error occurs
  - createParentDirs
```
@Beta
public static void createParentDirs(File file)
                                   throws IOException
```
    Creates any necessary but nonexistent parent directories of the specified file. Note that if this operation fails it may have succeeded in creating some (but not all) of the necessary parent directories.
    
    Throws:
    
    IOException - if an I/O error occurs, or if any necessary but nonexistent parent directories of the specified file could not be created.
    
    Since:
    
    4.0
  - move
```
@Beta
public static void move(File from,
                              File to)
                       throws IOException
```
    Moves a file from one path to another. This method can rename a file and/or move it to a different directory. In either case to must be the target path for the file itself; not just the new name for the file or the path to the new parent directory.
    Path equivalent: Files.move(java.nio.file.Path, java.nio.file.Path, java.nio.file.CopyOption...).
    
    Parameters:
    
    from - the source file
    
    to - the destination file
    
    Throws:
    
    IOException - if an I/O error occurs
    
    IllegalArgumentException - if from.equals(to)
  - readFirstLine
```
@Beta
 @Deprecated
public static String readFirstLine(File file,
                                                      Charset charset)
                                               throws IOException
```
    Deprecated. Prefer asCharSource(file, charset).readFirstLine(). This method is scheduled to be removed in January 2019.
    
    Reads the first line from a file. The line does not include line-termination characters, but does include other leading and trailing whitespace.
    
    Parameters:
    
    file - the file to read from
    
    charset - the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
    
    Returns:
    
    the first line, or null if the file is empty
    
    Throws:
    
    IOException - if an I/O error occurs
  - readLines
```
@Beta
public static List<String> readLines(File file,
                                           Charset charset)
                                    throws IOException
```
    Reads all of the lines from a file. The lines do not include line-termination characters, but do include other leading and trailing whitespace.
    This method returns a mutable List. For an ImmutableList, use Files.asCharSource(file, charset).readLines().
    Path equivalent: Files.readAllLines(java.nio.file.Path, Charset).
    
    Parameters:
    
    file - the file to read from
    
    charset - the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
    
    Returns:
    
    a mutable List containing all the lines
    
    Throws:
    
    IOException - if an I/O error occurs
  - readLines
```
@Beta
 @Deprecated
 @CanIgnoreReturnValue
public static <T> T readLines(File file,
                                                                        Charset charset,
                                                                        LineProcessor<T> callback)
                                                                 throws IOException
```
    Deprecated. Prefer asCharSource(file, charset).readLines(callback). This method is scheduled to be removed in January 2019.
    
    Streams lines from a File, stopping when our callback returns false, or we have read all of the lines.
    
    Parameters:
    
    file - the file to read from
    
    charset - the charset used to decode the input stream; see StandardCharsets for helpful predefined constants
    
    callback - the LineProcessor to use to handle the lines
    
    Returns:
    
    the output of processing the lines
    
    Throws:
    
    IOException - if an I/O error occurs
  - readBytes
```
@Beta
 @Deprecated
 @CanIgnoreReturnValue
public static <T> T readBytes(File file,
                                                                        ByteProcessor<T> processor)
                                                                 throws IOException
```
    Deprecated. Prefer asByteSource(file).read(processor). This method is scheduled to be removed in January 2019.
    
    Process the bytes of a file.
    (If this seems too complicated, maybe you're looking for toByteArray(java.io.File).)
    
    Parameters:
    
    file - the file to read
    
    processor - the object to which the bytes of the file are passed.
    
    Returns:
    
    the result of the byte processor
    
    Throws:
    
    IOException - if an I/O error occurs
  - hash
```
@Beta
 @Deprecated
public static HashCode hash(File file,
                                               HashFunction hashFunction)
                                        throws IOException
```
    Deprecated. Prefer asByteSource(file).hash(hashFunction). This method is scheduled to be removed in January 2019.
    
    Computes the hash code of the file using hashFunction.
    
    Parameters:
    
    file - the file to read
    
    hashFunction - the hash function to use to hash the data
    
    Returns:
    
    the HashCode of all of the bytes in the file
    
    Throws:
    
    IOException - if an I/O error occurs
    
    Since:
    
    12.0
  - map
```
@Beta
public static MappedByteBuffer map(File file)
                                  throws IOException
```
    Fully maps a file read-only in to memory as per FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long).
    Files are mapped from offset 0 to its length.
    This only works for files ≤ Integer.MAX_VALUE bytes.
    
    Parameters:
    
    file - the file to map
    
    Returns:
    
    a read-only buffer reflecting file
    
    Throws:
    
    FileNotFoundException - if the file does not exist
    
    IOException - if an I/O error occurs
    
    Since:
    
    2.0
    
    See Also:
    
    FileChannel.map(MapMode, long, long)
  - map
```
@Beta
public static MappedByteBuffer map(File file,
                                         FileChannel.MapMode mode)
                                  throws IOException
```
    Fully maps a file in to memory as per FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long) using the requested FileChannel.MapMode.
    Files are mapped from offset 0 to its length.
    This only works for files ≤ Integer.MAX_VALUE bytes.
    
    Parameters:
    
    file - the file to map
    
    mode - the mode to use when mapping file
    
    Returns:
    
    a buffer reflecting file
    
    Throws:
    
    FileNotFoundException - if the file does not exist
    
    IOException - if an I/O error occurs
    
    Since:
    
    2.0
    
    See Also:
    
    FileChannel.map(MapMode, long, long)
  - map
```
@Beta
public static MappedByteBuffer map(File file,
                                         FileChannel.MapMode mode,
                                         long size)
                                  throws IOException
```
    Maps a file in to memory as per FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long) using the requested FileChannel.MapMode.
    Files are mapped from offset 0 to size.
    If the mode is FileChannel.MapMode.READ_WRITE and the file does not exist, it will be created with the requested size. Thus this method is useful for creating memory mapped files which do not yet exist.
    This only works for files ≤ Integer.MAX_VALUE bytes.
    
    Parameters:
    
    file - the file to map
    
    mode - the mode to use when mapping file
    
    Returns:
    
    a buffer reflecting file
    
    Throws:
    
    IOException - if an I/O error occurs
    
    Since:
    
    2.0
    
    See Also:
    
    FileChannel.map(MapMode, long, long)
  - simplifyPath
```
@Beta
public static String simplifyPath(String pathname)
```
    Returns the lexically cleaned form of the path name, usually (but not always) equivalent to the original. The following heuristics are used:
    - empty string becomes .
    - . stays as .
    - fold out ./
    - fold out ../ when possible
    - collapse multiple slashes
    - delete trailing slashes (unless the path is just "/")
    These heuristics do not always match the behavior of the filesystem. In particular, consider the path a/../b, which simplifyPath will change to b. If a is a symlink to x, a/../b may refer to a sibling of x, rather than the sibling of a referred to by b.
    Since:
    
    11.0
  - getFileExtension
```
@Beta
public static String getFileExtension(String fullName)
```
    Returns the file extension for the given file name, or the empty string if the file has no extension. The result does not include the '.'.
    Note: This method simply returns everything after the last '.' in the file's name as determined by File.getName(). It does not account for any filesystem-specific behavior that the File API does not already account for. For example, on NTFS it will report "txt" as the extension for the filename "foo.exe:.txt" even though NTFS will drop the ":.txt" part of the name when the file is actually created on the filesystem due to NTFS's Alternate Data Streams.
    
    Since:
    
    11.0
  - getNameWithoutExtension
```
@Beta
public static String getNameWithoutExtension(String file)
```
    Returns the file name without its file extension or path. This is similar to the basename unix command. The result does not include the '.'.
    
    Parameters:
    
    file - The name of the file to trim the extension from. This can be either a fully qualified file name (including a path) or just a file name.
    
    Returns:
    
    The file name without its path or extension.
    
    Since:
    
    14.0
  - fileTraverser
```
@Beta
public static Traverser<File> fileTraverser()
```
    Returns a Traverser instance for the file and directory tree. The returned traverser starts from a File and will return all files and directories it encounters.
    Warning: File provides no support for symbolic links, and as such there is no way to ensure that a symbolic link to a directory is not followed when traversing the tree. In this case, iterables created by this traverser could contain files that are outside of the given directory or even be infinite if there is a symbolic link loop.
    If available, consider using MoreFiles.fileTraverser() instead. It behaves the same except that it doesn't follow symbolic links and returns Path instances.
    If the File passed to one of the Traverser methods does not exist or is not a directory, no exception will be thrown and the returned Iterable will contain a single element: that file.
    Example: Files.fileTraverser().depthFirstPreOrder(new File("/")) may return files with the following paths: ["/", "/etc", "/etc/config.txt", "/etc/fonts", "/home", "/home/alice", ...]
    
    Since:
    
    23.5
  - isDirectory
```
@Beta
public static Predicate<File> isDirectory()
```
    Returns a predicate that returns the result of File.isDirectory() on input files.
    
    Since:
    
    15.0
  - isFile
```
@Beta
public static Predicate<File> isFile()
```
    Returns a predicate that returns the result of File.isFile() on input files.
    
    Since:
    
    15.0

Class Files

Method Summary

Methods inherited from class java.lang.Object

Method Detail

newReader

newWriter

asByteSource

asByteSink

asCharSource

asCharSink

toByteArray

toString

write

write

copy

copy

copy

append

equal

createTempDir

touch

createParentDirs

move

readFirstLine

readLines

readLines

readBytes

hash

map

map

map

simplifyPath

getFileExtension

getNameWithoutExtension

fileTraverser

isDirectory

isFile