Class IOUtil
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
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).
- Since:
- 4.0
- Author:
- Peter Donald, Jeff Turner
-
Method Summary
Modifier and TypeMethodDescriptionstatic void
bufferedCopy
(InputStream input, OutputStream output) Deprecated.Buffering streams is actively harmful! See the class description as to why.static void
close
(InputStream inputStream) Deprecated.use try-with-resources insteadstatic void
close
(OutputStream outputStream) Deprecated.use try-with-resources insteadstatic void
Deprecated.use try-with-resources insteadstatic void
Deprecated.use try-with-resources insteadstatic void
Deprecated.use try-with-resources insteadstatic boolean
contentEquals
(InputStream input1, InputStream input2) Compare the contents of two Streams to determine if they are equal or not.static void
copy
(byte[] input, OutputStream output) Copy bytes from abyte[]
to anOutputStream
.static void
copy
(byte[] input, OutputStream output, int bufferSize) Copy bytes from abyte[]
to anOutputStream
.static void
Copy and convert bytes from abyte[]
to chars on aWriter
.static void
Copy and convert bytes from abyte[]
to chars on aWriter
.static void
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.static void
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.static void
copy
(InputStream input, OutputStream output) Copy bytes from anInputStream
to anOutputStream
.static void
copy
(InputStream input, OutputStream output, int bufferSize) Copy bytes from anInputStream
to anOutputStream
.static void
copy
(InputStream input, Writer output) Copy and convert bytes from anInputStream
to chars on aWriter
.static void
copy
(InputStream input, Writer output, int bufferSize) Copy and convert bytes from anInputStream
to chars on aWriter
.static void
copy
(InputStream input, Writer output, String encoding) Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.static void
copy
(InputStream input, Writer output, String encoding, int bufferSize) Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.static void
copy
(Reader input, OutputStream output) Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.static void
copy
(Reader input, OutputStream output, int bufferSize) Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.static void
Copy chars from aReader
to aWriter
.static void
Copy chars from aReader
to aWriter
.static void
copy
(String input, OutputStream output) Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.static void
copy
(String input, OutputStream output, int bufferSize) Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.static void
Copy chars from aString
to aWriter
.static byte[]
toByteArray
(InputStream input) static byte[]
toByteArray
(InputStream input, int bufferSize) static byte[]
toByteArray
(Reader input) static byte[]
toByteArray
(Reader input, int bufferSize) static byte[]
toByteArray
(String input) static byte[]
toByteArray
(String input, int bufferSize) static String
toString
(byte[] input) static String
toString
(byte[] input, int bufferSize) static String
static String
static String
toString
(InputStream input) static String
toString
(InputStream input, int bufferSize) static String
toString
(InputStream input, String encoding) static String
toString
(InputStream input, String encoding, int bufferSize) static String
static String
-
Method Details
-
copy
Copy bytes from anInputStream
to anOutputStream
.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Copy bytes from anInputStream
to anOutputStream
.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
copy
Copy chars from aReader
to aWriter
.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Copy chars from aReader
to aWriter
.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
copy
Copy and convert bytes from anInputStream
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Copy and convert bytes from anInputStream
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
copy
Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.- Parameters:
input
- to convertoutput
- the resultencoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
IOException
- io issue
-
copy
public static void copy(InputStream input, Writer output, String encoding, int bufferSize) throws IOException Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.- Parameters:
input
- to convertoutput
- the resultencoding
- 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.- Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convert- Returns:
- Get the contents of an
InputStream
as a String. The platform's default encoding is used for the byte-to-char conversion. - Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convertbufferSize
- Size of internal buffer to use.- Returns:
- Get the contents of an
InputStream
as a String. The platform's default encoding is used for the byte-to-char conversion. - Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convertencoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Returns:
- Get the contents of an
InputStream
as a String. - Throws:
IOException
- io issue
-
toString
public static String toString(InputStream input, String encoding, int bufferSize) throws IOException - Parameters:
input
- to convertencoding
- 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.- Returns:
- Get the contents of an
InputStream
as a String. - Throws:
IOException
- io issue
-
toByteArray
- Parameters:
input
- to convert- Returns:
- Get the contents of an
InputStream
as abyte[]
. - Throws:
IOException
- io issue
-
toByteArray
- Parameters:
input
- to convertbufferSize
- Size of internal buffer to use.- Returns:
- Get the contents of an
InputStream
as abyte[]
. - Throws:
IOException
- io issue
-
copy
Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convert- Returns:
- Get the contents of a
Reader
as a String. - Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convertbufferSize
- Size of internal buffer to use.- Returns:
- Get the contents of a
Reader
as a String. - Throws:
IOException
- io issue
-
toByteArray
- Parameters:
input
- to convert- Returns:
- Get the contents of a
Reader
as abyte[]
. - Throws:
IOException
- io issue
-
toByteArray
- Parameters:
input
- to convertbufferSize
- Size of internal buffer to use.- Returns:
- Get the contents of a
Reader
as abyte[]
. - Throws:
IOException
- io issue
-
copy
Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
copy
Copy chars from aString
to aWriter
.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
bufferedCopy
@Deprecated public static void bufferedCopy(InputStream input, OutputStream output) throws IOException Deprecated.Buffering streams is actively harmful! See the class description as to why. Usecopy(InputStream, OutputStream)
instead.Copy bytes from anInputStream
to anOutputStream
, with buffering. This is equivalent to passing aBufferedInputStream
andBufferedOutputStream
tocopy(InputStream, OutputStream)
, and flushing the output stream afterwards. The streams are not closed after the copy.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
toByteArray
- Parameters:
input
- to convert- Returns:
- Get the contents of a
String
as abyte[]
. - Throws:
IOException
- io issue
-
toByteArray
- Parameters:
input
- to convertbufferSize
- Size of internal buffer to use.- Returns:
- Get the contents of a
String
as abyte[]
. - Throws:
IOException
- io issue
-
copy
Copy and convert bytes from abyte[]
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Copy and convert bytes from abyte[]
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
copy
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.- Parameters:
input
- to convertoutput
- the resultencoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
IOException
- io issue
-
copy
public static void copy(byte[] input, Writer output, String encoding, int bufferSize) throws IOException Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.- Parameters:
input
- to convertoutput
- the resultencoding
- 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.- Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convert- Returns:
- Get the contents of a
byte[]
as a String. The platform's default encoding is used for the byte-to-char conversion. - Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convertbufferSize
- Size of internal buffer to use.- Returns:
- Get the contents of a
byte[]
as a String. The platform's default encoding is used for the byte-to-char conversion. - Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convertencoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Returns:
- Get the contents of a
byte[]
as a String. - Throws:
IOException
- io issue
-
toString
- Parameters:
input
- to convertencoding
- 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.- Returns:
- the contents of a
byte[]
as a String. - Throws:
IOException
- io issue
-
copy
Copy bytes from abyte[]
to anOutputStream
.- Parameters:
input
- to convertoutput
- the result- Throws:
IOException
- io issue
-
copy
Copy bytes from abyte[]
to anOutputStream
.- Parameters:
input
- to convertoutput
- the resultbufferSize
- Size of internal buffer to use.- Throws:
IOException
- io issue
-
contentEquals
Compare the contents of two Streams to determine if they are equal or not.- Parameters:
input1
- the first streaminput2
- the second stream- Returns:
- true if the content of the streams are equal or they both don't exist, false otherwise
- Throws:
IOException
- io issue
-
close
Deprecated.use try-with-resources insteadCloses the input stream. The input stream can be null and any IOException's will be swallowed.- Parameters:
inputStream
- The stream to close.
-
close
Deprecated.use try-with-resources insteadCloses a channel. Channel can be null and any IOException's will be swallowed.- Parameters:
channel
- The stream to close.
-
close
Deprecated.use try-with-resources insteadCloses the output stream. The output stream can be null and any IOException's will be swallowed.- Parameters:
outputStream
- The stream to close.
-
close
Deprecated.use try-with-resources insteadCloses the reader. The reader can be null and any IOException's will be swallowed.- Parameters:
reader
- The reader to close.
-
close
Deprecated.use try-with-resources insteadCloses the writer. The writer can be null and any IOException's will be swallowed.- Parameters:
writer
- The writer to close.
-