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java.lang.Objectorg.apache.commons.io.CopyUtils
public class CopyUtils
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.
Origin of code: Apache Avalon (Excalibur)
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 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 int |
copy(Reader input,
Writer output)
Copy chars from a Reader to a Writer . |
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 . |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
---|
public CopyUtils()
Method Detail |
---|
public static void copy(byte[] input, OutputStream output) throws IOException
byte[]
to an OutputStream
.
input
- the byte array to read fromoutput
- the OutputStream
to write to
IOException
- In case of an I/O problempublic static void copy(byte[] input, Writer output) throws IOException
byte[]
to chars on a
Writer
.
The platform's default encoding is used for the byte-to-char conversion.
input
- the byte array to read fromoutput
- the Writer
to write to
IOException
- In case of an I/O problempublic static void copy(byte[] input, Writer output, String encoding) throws IOException
byte[]
to chars on a
Writer
, using the specified encoding.
input
- the byte array to read fromoutput
- the Writer
to write toencoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
IOException
- In case of an I/O problempublic static int copy(InputStream input, OutputStream output) throws IOException
InputStream
to an OutputStream
.
input
- the InputStream
to read fromoutput
- the OutputStream
to write to
IOException
- In case of an I/O problempublic static int copy(Reader input, Writer output) throws IOException
Reader
to a Writer
.
input
- the Reader
to read fromoutput
- the Writer
to write to
IOException
- In case of an I/O problempublic static void copy(InputStream input, Writer output) throws IOException
InputStream
to chars on a
Writer
.
The platform's default encoding is used for the byte-to-char conversion.
input
- the InputStream
to read fromoutput
- the Writer
to write to
IOException
- In case of an I/O problempublic static void copy(InputStream input, Writer output, String encoding) throws IOException
InputStream
to chars on a
Writer
, using the specified encoding.
input
- the InputStream
to read fromoutput
- the Writer
to write toencoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
IOException
- In case of an I/O problempublic static void copy(Reader input, OutputStream output) throws IOException
Reader
to bytes on an
OutputStream
, and flush the OutputStream
.
input
- the Reader
to read fromoutput
- the OutputStream
to write to
IOException
- In case of an I/O problempublic static void copy(String input, OutputStream output) throws IOException
String
to bytes on an OutputStream
, and
flush the OutputStream
.
input
- the String
to read fromoutput
- the OutputStream
to write to
IOException
- In case of an I/O problempublic static void copy(String input, Writer output) throws IOException
String
to a Writer
.
input
- the String
to read fromoutput
- the Writer
to write to
IOException
- In case of an I/O problem
|
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