org.apache.commons.io
public class CopyUtils extends Object
Deprecated: Use IOUtils. Will be removed in 2.0. Methods renamed to IOUtils.write() or IOUtils.copy(). Null handling behaviour 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.
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
java.io.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.
Origin of code: Excalibur.
Version: $Id: CopyUtils.java 437680 2006-08-28 11:57:00Z scolebourne $
Field Summary | |
---|---|
static int | DEFAULT_BUFFER_SIZE
The default size of the buffer. |
Constructor Summary | |
---|---|
CopyUtils()
Instances should NOT be constructed in standard programming. |
Method Summary | |
---|---|
static void | copy(byte[] input, OutputStream output)
Copy bytes from a byte[] to an OutputStream . |
static void | copy(byte[] input, Writer output)
Copy and convert bytes from a byte[] to chars on a
Writer .
|
static void | copy(byte[] input, Writer output, String encoding)
Copy and convert bytes from a byte[] to chars on a
Writer , using the specified encoding. |
static int | copy(InputStream input, OutputStream output)
Copy bytes from an InputStream to an
OutputStream . |
static int | copy(Reader input, Writer output)
Copy chars from a Reader to a Writer . |
static void | copy(InputStream input, Writer output)
Copy and convert bytes from an InputStream to chars on a
Writer .
|
static void | copy(InputStream input, Writer output, String encoding)
Copy and convert bytes from an InputStream to chars on a
Writer , using the specified encoding. |
static void | copy(Reader input, OutputStream output)
Serialize chars from a Reader to bytes on an
OutputStream , and flush the OutputStream . |
static void | copy(String input, OutputStream output)
Serialize chars from a String to bytes on an
OutputStream , and
flush the OutputStream . |
static void | copy(String input, Writer output)
Copy chars from a String to a Writer . |
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
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
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
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
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
InputStream
to chars on a
Writer
.
The platform's default encoding is used for the 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
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
Reader
to bytes on an
OutputStream
, and flush the OutputStream
.Parameters: input the Reader
to read from output the OutputStream
to write to
Throws: IOException In case of an I/O problem
String
to bytes on an
OutputStream
, and
flush the OutputStream
.Parameters: input the String
to read from output the OutputStream
to write to
Throws: IOException In case of an I/O problem
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