General IO Stream manipulation.
This class provides static utility methods for input/output operations, particularly 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 each
copy
method, a variant is provided that allows the caller to specify the
buffer size (the default is 4k). As the buffer size can have a fairly large impact on speed, this
may be worth tweaking. Often "large buffer -> faster" does not hold, even for large data
transfers.
For byte-to-char methods, a
copy
variant allows the encoding to be selected
(otherwise the platform default is used).
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).
bufferedCopy
public static void bufferedCopy(InputStream input,
OutputStream output)
throws IOException
Buffering streams is actively harmful! See the class description as to why. Use
copy(InputStream,OutputStream)
instead.
Copy bytes from an
InputStream
to an
OutputStream
, with buffering.
This is equivalent to passing a
java.io.BufferedInputStream
and
java.io.BufferedOutputStream
to
copy(InputStream,OutputStream)
,
and flushing the output stream afterwards. The streams are not closed
after the copy.
close
public static void close(InputStream inputStream)
Closes the input stream. The input stream can be null and any IOException's will be swallowed.
inputStream
- The stream to close.
close
public static void close(OutputStream outputStream)
Closes the output stream. The output stream can be null and any IOException's will be swallowed.
outputStream
- The stream to close.
close
public static void close(Reader reader)
Closes the reader. The reader can be null and any IOException's will be swallowed.
reader
- The reader to close.
close
public static void close(Writer writer)
Closes the writer. The writer can be null and any IOException's will be swallowed.
contentEquals
public static boolean contentEquals(InputStream input1,
InputStream input2)
throws IOException
Compare the contents of two Streams to determine if they are equal or not.
input1
- the first streaminput2
- the second stream
- true if the content of the streams are equal or they both don't exist, false otherwise
copy
public static void copy(InputStream input,
OutputStream output)
throws IOException
Copy bytes from an InputStream
to an OutputStream
.
copy
public static void copy(InputStream input,
OutputStream output,
int bufferSize)
throws IOException
Copy bytes from an InputStream
to an OutputStream
.
bufferSize
- Size of internal buffer to use.
copy
public static void copy(InputStream input,
Writer output)
throws IOException
Copy and convert bytes from an InputStream
to chars on a
Writer
.
The platform's default encoding is used for the byte-to-char conversion.
copy
public static void copy(InputStream input,
Writer output,
String encoding)
throws IOException
Copy and convert bytes from an InputStream
to chars on a
Writer
, using the specified encoding.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
copy
public static void copy(InputStream input,
Writer output,
String encoding,
int bufferSize)
throws IOException
Copy and convert bytes from an InputStream
to chars on a
Writer
, using the specified encoding.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.bufferSize
- Size of internal buffer to use.
copy
public static void copy(InputStream input,
Writer output,
int bufferSize)
throws IOException
Copy and convert bytes from an InputStream
to chars on a
Writer
.
The platform's default encoding is used for the byte-to-char conversion.
bufferSize
- Size of internal buffer to use.
copy
public static void copy(Reader input,
OutputStream output)
throws IOException
Serialize chars from a Reader
to bytes on an OutputStream
, and
flush the OutputStream
.
copy
public static void copy(Reader input,
OutputStream output,
int bufferSize)
throws IOException
Serialize chars from a Reader
to bytes on an OutputStream
, and
flush the OutputStream
.
bufferSize
- Size of internal buffer to use.
copy
public static void copy(Reader input,
Writer output)
throws IOException
Copy chars from a Reader
to a Writer
.
copy
public static void copy(Reader input,
Writer output,
int bufferSize)
throws IOException
Copy chars from a Reader
to a Writer
.
bufferSize
- Size of internal buffer to use.
copy
public static void copy(String input,
OutputStream output)
throws IOException
Serialize chars from a String
to bytes on an OutputStream
, and
flush the OutputStream
.
copy
public static void copy(String input,
OutputStream output,
int bufferSize)
throws IOException
Serialize chars from a String
to bytes on an OutputStream
, and
flush the OutputStream
.
bufferSize
- Size of internal buffer to use.
copy
public static void copy(String input,
Writer output)
throws IOException
Copy chars from a String
to a Writer
.
copy
public static void copy(byte[] input,
OutputStream output)
throws IOException
Copy bytes from a byte[]
to an OutputStream
.
copy
public static void copy(byte[] input,
OutputStream output,
int bufferSize)
throws IOException
Copy bytes from a byte[]
to an OutputStream
.
bufferSize
- Size of internal buffer to use.
copy
public static void copy(byte[] input,
Writer output)
throws IOException
Copy and convert bytes from a byte[]
to chars on a
Writer
.
The platform's default encoding is used for the byte-to-char conversion.
copy
public static void copy(byte[] input,
Writer output,
String encoding)
throws IOException
Copy and convert bytes from a byte[]
to chars on a
Writer
, using the specified encoding.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
copy
public static void copy(byte[] input,
Writer output,
String encoding,
int bufferSize)
throws IOException
Copy and convert bytes from a byte[]
to chars on a
Writer
, using the specified encoding.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.bufferSize
- Size of internal buffer to use.
copy
public static void copy(byte[] input,
Writer output,
int bufferSize)
throws IOException
Copy and convert bytes from a byte[]
to chars on a
Writer
.
The platform's default encoding is used for the byte-to-char conversion.
bufferSize
- Size of internal buffer to use.
toByteArray
public static byte[] toByteArray(InputStream input)
throws IOException
Get the contents of an InputStream
as a byte[]
.
toByteArray
public static byte[] toByteArray(InputStream input,
int bufferSize)
throws IOException
Get the contents of an InputStream
as a byte[]
.
bufferSize
- Size of internal buffer to use.
toByteArray
public static byte[] toByteArray(Reader input)
throws IOException
Get the contents of a Reader
as a byte[]
.
toByteArray
public static byte[] toByteArray(Reader input,
int bufferSize)
throws IOException
Get the contents of a Reader
as a byte[]
.
bufferSize
- Size of internal buffer to use.
toByteArray
public static byte[] toByteArray(String input)
throws IOException
Get the contents of a String
as a byte[]
.
toByteArray
public static byte[] toByteArray(String input,
int bufferSize)
throws IOException
Get the contents of a String
as a byte[]
.
bufferSize
- Size of internal buffer to use.
toString
public static String toString(InputStream input)
throws IOException
Get the contents of an InputStream
as a String.
The platform's default encoding is used for the byte-to-char conversion.
toString
public static String toString(InputStream input,
String encoding)
throws IOException
Get the contents of an InputStream
as a String.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
toString
public static String toString(InputStream input,
String encoding,
int bufferSize)
throws IOException
Get the contents of an InputStream
as a String.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.bufferSize
- Size of internal buffer to use.
toString
public static String toString(InputStream input,
int bufferSize)
throws IOException
Get the contents of an InputStream
as a String.
The platform's default encoding is used for the byte-to-char conversion.
bufferSize
- Size of internal buffer to use.
toString
public static String toString(Reader input)
throws IOException
Get the contents of a Reader
as a String.
toString
public static String toString(Reader input,
int bufferSize)
throws IOException
Get the contents of a Reader
as a String.
bufferSize
- Size of internal buffer to use.
toString
public static String toString(byte[] input)
throws IOException
Get the contents of a byte[]
as a String.
The platform's default encoding is used for the byte-to-char conversion.
toString
public static String toString(byte[] input,
String encoding)
throws IOException
Get the contents of a byte[]
as a String.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.
toString
public static String toString(byte[] input,
String encoding,
int bufferSize)
throws IOException
Get the contents of a byte[]
as a String.
encoding
- The name of a supported character encoding. See the
IANA
Charset Registry for a list of valid encoding types.bufferSize
- Size of internal buffer to use.
toString
public static String toString(byte[] input,
int bufferSize)
throws IOException
Get the contents of a byte[]
as a String.
The platform's default encoding is used for the byte-to-char conversion.
bufferSize
- Size of internal buffer to use.