Package org.apache.commons.io

# Class CopyUtils

java.lang.Object
org.apache.commons.io.CopyUtils

@Deprecated public class CopyUtils extends Object
Deprecated.
Use IOUtils. Will be removed in 3.0. Methods renamed to IOUtils.write() or IOUtils.copy(). Null handling behavior changed in IOUtils (null data does not throw NullPointerException).
This class provides static utility methods for buffered copying between sources (`InputStream`, `Reader`, `String` and `byte[]`) and destinations (`OutputStream`, `Writer`, `String` and `byte[]`).

Unless otherwise noted, these `copy` methods do not flush or close the streams. Often doing so would require making non-portable assumptions about the streams' origin and further use. This means that both streams' `close()` methods must be called after copying. if one omits this step, then the stream resources (sockets, file descriptors) are released when the associated Stream is garbage-collected. It is not a good idea to rely on this mechanism. For a good overview of the distinction between "memory management" and "resource management", see this UnixReview article.

For byte-to-char methods, a `copy` variant allows the encoding to be selected (otherwise the platform default is used). We would like to encourage you to always specify the encoding because relying on the platform default can lead to unexpected results.

We don't provide special variants for the `copy` methods that let you specify the buffer size because in modern VMs the impact on speed seems to be minimal. We're using a default buffer size of 4 KB.

The `copy` methods use an internal buffer when copying. It is therefore advisable not to deliberately wrap the stream arguments to the `copy` methods in `Buffered*` streams. For example, don't do the following:

      copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );

The rationale is as follows:

Imagine that an InputStream's read() is a very expensive operation, which would usually suggest wrapping in a BufferedInputStream. The BufferedInputStream works by issuing infrequent `InputStream.read(byte[] b, int off, int len)` requests on the underlying InputStream, to fill an internal buffer, from which further `read` requests can inexpensively get their data (until the buffer runs out).

However, the `copy` methods do the same thing, keeping an internal buffer, populated by `InputStream.read(byte[] b, int off, int len)` requests. Having two buffers (or three if the destination stream is also buffered) is pointless, and the unnecessary buffer management hurts performance slightly (about 3%, according to some simple experiments).

Behold, intrepid explorers; a map of this class:

           Method      Input               Output          Dependency
           ------      -----               ------          -------
     1     copy        InputStream         OutputStream    (primitive)
     2     copy        Reader              Writer          (primitive)

     3     copy        InputStream         Writer          2

     4     copy        Reader              OutputStream    2

     5     copy        String              OutputStream    2
     6     copy        String              Writer          (trivial)

     7     copy        byte[]              Writer          3
     8     copy        byte[]              OutputStream    (trivial)

Note that only the first two methods shuffle bytes; the rest use these two, or (if possible) copy using native Java copy methods. As there are method variants to specify the encoding, each row may correspond to up to 2 methods.

Provenance: Excalibur.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `CopyUtils()`
  Deprecated.
  TODO Make private in 3.0.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static void`
  `copy(byte[] input, OutputStream output)`
  Deprecated.
  Copies bytes from a `byte[]` to an `OutputStream`.
  `static void`
  `copy(byte[] input, Writer output)`
  Deprecated.
  Use `copy(byte[], Writer, String)` instead
  `static void`
  `copy(byte[] input, Writer output, String encoding)`
  Deprecated.
  Copies and convert bytes from a `byte[]` to chars on a `Writer`, using the specified encoding.
  `static int`
  `copy(InputStream input, OutputStream output)`
  Deprecated.
  Copies bytes from an `InputStream` to an `OutputStream`.
  `static void`
  `copy(InputStream input, Writer output)`
  Deprecated.
  Use `copy(InputStream, Writer, String)` instead
  `static void`
  `copy(InputStream input, Writer output, String encoding)`
  Deprecated.
  Copies and convert bytes from an `InputStream` to chars on a `Writer`, using the specified encoding.
  `static void`
  `copy(Reader input, OutputStream output)`
  Deprecated.
  Use `copy(Reader, OutputStream, String)` instead
  `static void`
  `copy(Reader input, OutputStream output, String encoding)`
  Deprecated.
  Serialize chars from a `Reader` to bytes on an `OutputStream`, and flush the `OutputStream`.
  `static int`
  `copy(Reader input, Writer output)`
  Deprecated.
  Copies chars from a `Reader` to a `Writer`.
  `static void`
  `copy(String input, OutputStream output)`
  Deprecated.
  Use `copy(String, OutputStream, String)` instead
  `static void`
  `copy(String input, OutputStream output, String encoding)`
  Deprecated.
  Serialize chars from a `String` to bytes on an `OutputStream`, and flush the `OutputStream`.
  `static void`
  `copy(String input, Writer output)`
  Deprecated.
  Copies chars from a `String` to a `Writer`.

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

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

- ## Constructor Details

  - ### CopyUtils

    @Deprecated public CopyUtils()
    Deprecated.
    TODO Make private in 3.0.
    Instances should NOT be constructed in standard programming.

- ## Method Details

  - ### copy

    public static void copy(byte[] input, OutputStream output) throws IOException
    Deprecated.
    Copies bytes from a `byte[]` to an `OutputStream`.
    Parameters:
      `input` - the byte array to read from
      `output` - the `OutputStream` to write to
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    @Deprecated public static void copy(byte[] input, Writer output) throws IOException
    Deprecated.
    Use `copy(byte[], Writer, String)` instead
    Copies and convert bytes from a `byte[]` to chars on a `Writer`. The platform's default encoding is used for the byte-to-char conversion.
    Parameters:
      `input` - the byte array to read from
      `output` - the `Writer` to write to
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    public static void copy(byte[] input, Writer output, String encoding) throws IOException
    Deprecated.
    Copies and convert bytes from a `byte[]` to chars on a `Writer`, using the specified encoding.
    Parameters:
      `input` - the byte array to read from
      `output` - the `Writer` to write to
      `encoding` - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    public static int copy(InputStream input, OutputStream output) throws IOException
    Deprecated.
    Copies bytes from an `InputStream` to an `OutputStream`.
    Parameters:
      `input` - the `InputStream` to read from
      `output` - the `OutputStream` to write to
    Returns:
      the number of bytes copied
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    @Deprecated public static void copy(InputStream input, Writer output) throws IOException
    Deprecated.
    Use `copy(InputStream, Writer, String)` instead
    Copies and convert bytes from an `InputStream` to chars on a `Writer`.

    This method uses the virtual machine's `default charset` for byte-to-char conversion.

    Parameters:
      `input` - the `InputStream` to read from
      `output` - the `Writer` to write to
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    public static void copy(InputStream input, Writer output, String encoding) throws IOException
    Deprecated.
    Copies and convert bytes from an `InputStream` to chars on a `Writer`, using the specified encoding.
    Parameters:
      `input` - the `InputStream` to read from
      `output` - the `Writer` to write to
      `encoding` - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    @Deprecated public static void copy(Reader input, OutputStream output) throws IOException
    Deprecated.
    Use `copy(Reader, OutputStream, String)` instead
    Serialize chars from a `Reader` to bytes on an `OutputStream`, and flush the `OutputStream`.

    This method uses the virtual machine's `default charset` for byte-to-char conversion.

    Parameters:
      `input` - the `Reader` to read from
      `output` - the `OutputStream` to write to
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    public static void copy(Reader input, OutputStream output, String encoding) throws IOException
    Deprecated.
    Serialize chars from a `Reader` to bytes on an `OutputStream`, and flush the `OutputStream`.
    Parameters:
      `input` - the `Reader` to read from
      `output` - the `OutputStream` to write to
      `encoding` - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
    Throws:
      `IOException` - In case of an I/O problem
    Since:
      2.5

  - ### copy

    public static int copy(Reader input, Writer output) throws IOException
    Deprecated.
    Copies chars from a `Reader` to a `Writer`.
    Parameters:
      `input` - the `Reader` to read from
      `output` - the `Writer` to write to
    Returns:
      the number of characters copied
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    @Deprecated public static void copy(String input, OutputStream output) throws IOException
    Deprecated.
    Use `copy(String, OutputStream, String)` instead
    Serialize chars from a `String` to bytes on an `OutputStream`, and flush the `OutputStream`.

    This method uses the virtual machine's `default charset` for byte-to-char conversion.

    Parameters:
      `input` - the `String` to read from
      `output` - the `OutputStream` to write to
    Throws:
      `IOException` - In case of an I/O problem

  - ### copy

    public static void copy(String input, OutputStream output, String encoding) throws IOException
    Deprecated.
    Serialize chars from a `String` to bytes on an `OutputStream`, and flush the `OutputStream`.
    Parameters:
      `input` - the `String` to read from
      `output` - the `OutputStream` to write to
      `encoding` - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
    Throws:
      `IOException` - In case of an I/O problem
    Since:
      2.5

  - ### copy

    public static void copy(String input, Writer output) throws IOException
    Deprecated.
    Copies chars from a `String` to a `Writer`.
    Parameters:
      `input` - the `String` to read from
      `output` - the `Writer` to write to
    Throws:
      `IOException` - In case of an I/O problem