Package org.apache.lucene.util

# Class IOUtils

java.lang.Object
org.apache.lucene.util.IOUtils

public final class IOUtils extends Object
Utilities for dealing with `Closeable`s.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `UTF_8`
  UTF-8 charset string.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static <T> void`
  `applyToAll(Collection<T> collection, IOConsumer<T> consumer)`
  Applies the consumer to all non-null elements in the collection even if an exception is thrown.
  `static void`
  `close(Closeable... objects)`
  Closes all given `Closeable`s.
  `static void`
  `close(Iterable<? extends Closeable> objects)`
  Closes all given `Closeable`s.
  `static void`
  `closeWhileHandlingException(Closeable... objects)`
  Closes all given `Closeable`s, suppressing all thrown exceptions.
  `static void`
  `closeWhileHandlingException(Iterable<? extends Closeable> objects)`
  Closes all given `Closeable`s, suppressing all thrown non `Error` exceptions.
  `static void`
  `deleteFiles(Directory dir, Collection<String> names)`
  Deletes all given file names.
  `static void`
  `deleteFilesIfExist(Path... files)`
  Deletes all given `Path`s, if they exist.
  `static void`
  `deleteFilesIfExist(Collection<? extends Path> files)`
  Deletes all given `Path`s, if they exist.
  `static void`
  `deleteFilesIgnoringExceptions(Path... files)`
  Deletes all given files, suppressing all thrown IOExceptions.
  `static void`
  `deleteFilesIgnoringExceptions(Collection<? extends Path> files)`
  Deletes all given files, suppressing all thrown IOExceptions.
  `static void`
  `deleteFilesIgnoringExceptions(Directory dir, String... files)`
  `static void`
  `deleteFilesIgnoringExceptions(Directory dir, Collection<String> files)`
  Deletes all given files, suppressing all thrown IOExceptions.
  `static void`
  `fsync(Path fileToSync, boolean isDir)`
  Ensure that any writes to the given file is written to the storage device that contains it.
  `static Reader`
  `getDecodingReader(InputStream stream, Charset charSet)`
  Wrapping the given `InputStream` in a reader using a `CharsetDecoder`.
  `static <T> T`
  `requireResourceNonNull(T resource, String name)`
  Wrap all calls to `Class.getResource(String)` or `Class.getResourceAsStream(String)` using this method to enforce existence of the resource.
  `static Error`
  `rethrowAlways(Throwable th)`
  This utility method takes a previously caught (non-null) `Throwable` and rethrows either the original argument if it was a subclass of the `IOException` or an `RuntimeException` with the cause set to the argument.
  `static void`
  `rm(Path... locations)`
  Deletes one or more files or directories (and everything underneath it).
  `static <T extends Throwable>
  T`
  `useOrSuppress(T first, T second)`
  Returns the second throwable if the first is null otherwise adds the second as suppressed to the first and returns it.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### UTF_8

    public static final String UTF_8
    UTF-8 charset string.

    Where possible, use `StandardCharsets.UTF_8` instead, as using the String constant may slow things down.

    See Also:
      - `StandardCharsets.UTF_8`

- ## Method Details

  - ### close

    public static void close(Closeable... objects) throws IOException
    Closes all given `Closeable`s. Some of the `Closeable`s may be null; they are ignored. After everything is closed, the method either throws the first exception it hit while closing, or completes normally if there were no exceptions.
    Parameters:
      `objects` - objects to call `close()` on
    Throws:
      `IOException`

  - ### close

    public static void close(Iterable<? extends Closeable> objects) throws IOException
    Closes all given `Closeable`s.
    Throws:
      `IOException`
    See Also:
      - `close(Closeable...)`

  - ### closeWhileHandlingException

    public static void closeWhileHandlingException(Closeable... objects)
    Closes all given `Closeable`s, suppressing all thrown exceptions. Some of the `Closeable`s may be null, they are ignored.
    Parameters:
      `objects` - objects to call `close()` on

  - ### closeWhileHandlingException

    public static void closeWhileHandlingException(Iterable<? extends Closeable> objects)
    Closes all given `Closeable`s, suppressing all thrown non `Error` exceptions. Even if a `Error` is thrown all given closeable are closed.
    See Also:
      - `closeWhileHandlingException(Closeable...)`

  - ### getDecodingReader

    public static Reader getDecodingReader(InputStream stream, Charset charSet)
    Wrapping the given `InputStream` in a reader using a `CharsetDecoder`. Unlike Java's defaults this reader will throw an exception if your it detects the read charset doesn't match the expected `Charset`.

    Decoding readers are useful to load configuration files, stopword lists or synonym files to detect character set problems. However, it's not recommended to use as a common purpose reader.

    Parameters:
      `stream` - the stream to wrap in a reader
      `charSet` - the expected charset
    Returns:
      a wrapping reader

  - ### requireResourceNonNull

    public static <T> T requireResourceNonNull(T resource, String name) throws IOException
    Wrap all calls to `Class.getResource(String)` or `Class.getResourceAsStream(String)` using this method to enforce existence of the resource. This code works around those methods returning `null` to signal non-existence.
    Parameters:
      `resource` - return value of above methods
      `name` - of resource
    Returns:
      the resource passed in if existent
    Throws:
      `FileNotFoundException` - if resource was not found
      `IOException`

  - ### deleteFilesIgnoringExceptions

    public static void deleteFilesIgnoringExceptions(Directory dir, Collection<String> files)
    Deletes all given files, suppressing all thrown IOExceptions.

    Note that the files should not be null.

  - ### deleteFilesIgnoringExceptions

    public static void deleteFilesIgnoringExceptions(Directory dir, String... files)

  - ### deleteFiles

    public static void deleteFiles(Directory dir, Collection<String> names) throws IOException
    Deletes all given file names. Some of the file names may be null; they are ignored. After everything is deleted, the method either throws the first exception it hit while deleting, or completes normally if there were no exceptions.
    Parameters:
      `dir` - Directory to delete files from
      `names` - file names to delete
    Throws:
      `IOException`

  - ### deleteFilesIgnoringExceptions

    public static void deleteFilesIgnoringExceptions(Path... files)
    Deletes all given files, suppressing all thrown IOExceptions.

    Some of the files may be null, if so they are ignored.

  - ### deleteFilesIgnoringExceptions

    public static void deleteFilesIgnoringExceptions(Collection<? extends Path> files)
    Deletes all given files, suppressing all thrown IOExceptions.

    Some of the files may be null, if so they are ignored.

  - ### deleteFilesIfExist

    public static void deleteFilesIfExist(Path... files) throws IOException
    Deletes all given `Path`s, if they exist. Some of the `File`s may be null; they are ignored. After everything is deleted, the method either throws the first exception it hit while deleting, or completes normally if there were no exceptions.
    Parameters:
      `files` - files to delete
    Throws:
      `IOException`

  - ### deleteFilesIfExist

    public static void deleteFilesIfExist(Collection<? extends Path> files) throws IOException
    Deletes all given `Path`s, if they exist. Some of the `File`s may be null; they are ignored. After everything is deleted, the method either throws the first exception it hit while deleting, or completes normally if there were no exceptions.
    Parameters:
      `files` - files to delete
    Throws:
      `IOException`

  - ### rm

    public static void rm(Path... locations) throws IOException
    Deletes one or more files or directories (and everything underneath it).
    Throws:
      `IOException` - if any of the given files (or their subhierarchy files in case of directories) cannot be removed.

  - ### rethrowAlways

    public static Error rethrowAlways(Throwable th) throws IOException, RuntimeException
    This utility method takes a previously caught (non-null) `Throwable` and rethrows either the original argument if it was a subclass of the `IOException` or an `RuntimeException` with the cause set to the argument.

    This method never returns any value, even though it declares a return value of type `Error`. The return value declaration is very useful to let the compiler know that the code path following the invocation of this method is unreachable. So in most cases the invocation of this method will be guarded by an `if` and used together with a `throw` statement, as in:

         if (t != null) throw IOUtils.rethrowAlways(t)

    Parameters:
      `th` - The throwable to rethrow, must not be null.
    Returns:
      This method always results in an exception, it never returns any value. See method documentation for details and usage example.
    Throws:
      `IOException` - if the argument was an instance of IOException
      `RuntimeException` - with the `Throwable.getCause()` set to the argument, if it was not an instance of IOException.

  - ### fsync

    public static void fsync(Path fileToSync, boolean isDir) throws IOException
    Ensure that any writes to the given file is written to the storage device that contains it.
    Parameters:
      `fileToSync` - the file to fsync
      `isDir` - if true, the given file is a directory (we open for read and ignore IOExceptions, because not all file systems and operating systems allow to fsync on a directory)
    Throws:
      `IOException`

  - ### useOrSuppress

    public static <T extends Throwable> T useOrSuppress(T first, T second)
    Returns the second throwable if the first is null otherwise adds the second as suppressed to the first and returns it.

  - ### applyToAll

    public static <T> void applyToAll(Collection<T> collection, IOConsumer<T> consumer) throws IOException
    Applies the consumer to all non-null elements in the collection even if an exception is thrown. The first exception thrown by the consumer is re-thrown and subsequent exceptions are suppressed.
    Throws:
      `IOException`