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
- Version:
- $Id$
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Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionstatic voidbufferedCopy(InputStream input, OutputStream output) Deprecated.Buffering streams is actively harmful! See the class description as to why.static voidclose(InputStream inputStream) Closes the input stream.static voidclose(OutputStream outputStream) Closes the output stream.static voidCloses the reader.static voidCloses the writer.static voidCloses a channel.static booleancontentEquals(InputStream input1, InputStream input2) Compare the contents of two Streams to determine if they are equal or not.static voidcopy(byte[] input, OutputStream output) Copy bytes from abyte[]to anOutputStream.static voidcopy(byte[] input, OutputStream output, int bufferSize) Copy bytes from abyte[]to anOutputStream.static voidCopy and convert bytes from abyte[]to chars on aWriter.static voidCopy and convert bytes from abyte[]to chars on aWriter.static voidCopy and convert bytes from abyte[]to chars on aWriter, using the specified encoding.static voidCopy and convert bytes from abyte[]to chars on aWriter, using the specified encoding.static voidcopy(InputStream input, OutputStream output) Copy bytes from anInputStreamto anOutputStream.static voidcopy(InputStream input, OutputStream output, int bufferSize) Copy bytes from anInputStreamto anOutputStream.static voidcopy(InputStream input, Writer output) Copy and convert bytes from anInputStreamto chars on aWriter.static voidcopy(InputStream input, Writer output, int bufferSize) Copy and convert bytes from anInputStreamto chars on aWriter.static voidcopy(InputStream input, Writer output, String encoding) Copy and convert bytes from anInputStreamto chars on aWriter, using the specified encoding.static voidcopy(InputStream input, Writer output, String encoding, int bufferSize) Copy and convert bytes from anInputStreamto chars on aWriter, using the specified encoding.static voidcopy(Reader input, OutputStream output) Serialize chars from aReaderto bytes on anOutputStream, and flush theOutputStream.static voidcopy(Reader input, OutputStream output, int bufferSize) Serialize chars from aReaderto bytes on anOutputStream, and flush theOutputStream.static voidCopy chars from aReaderto aWriter.static voidCopy chars from aReaderto aWriter.static voidcopy(String input, OutputStream output) Serialize chars from aStringto bytes on anOutputStream, and flush theOutputStream.static voidcopy(String input, OutputStream output, int bufferSize) Serialize chars from aStringto bytes on anOutputStream, and flush theOutputStream.static voidCopy chars from aStringto aWriter.static byte[]toByteArray(InputStream input) Get the contents of anInputStreamas abyte[].static byte[]toByteArray(InputStream input, int bufferSize) Get the contents of anInputStreamas abyte[].static byte[]toByteArray(Reader input) Get the contents of aReaderas abyte[].static byte[]toByteArray(Reader input, int bufferSize) Get the contents of aReaderas abyte[].static byte[]toByteArray(String input) Get the contents of aStringas abyte[].static byte[]toByteArray(String input, int bufferSize) Get the contents of aStringas abyte[].static StringtoString(byte[] input) Get the contents of abyte[]as a String.static StringtoString(byte[] input, int bufferSize) Get the contents of abyte[]as a String.static StringGet the contents of abyte[]as a String.static StringGet the contents of abyte[]as a String.static StringtoString(InputStream input) Get the contents of anInputStreamas a String.static StringtoString(InputStream input, int bufferSize) Get the contents of anInputStreamas a String.static StringtoString(InputStream input, String encoding) Get the contents of anInputStreamas a String.static StringtoString(InputStream input, String encoding, int bufferSize) Get the contents of anInputStreamas a String.static StringGet the contents of aReaderas a String.static StringGet the contents of aReaderas a String.
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Field Details
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DEFAULT_BUFFER_SIZE
private static final int DEFAULT_BUFFER_SIZE- See Also:
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Constructor Details
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IOUtil
private IOUtil()Private constructor to prevent instantiation.
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Method Details
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copy
Copy bytes from anInputStreamto anOutputStream.- Throws:
IOException
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copy
Copy bytes from anInputStreamto anOutputStream.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Copy chars from aReaderto aWriter.- Throws:
IOException
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copy
Copy chars from aReaderto aWriter.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Copy and convert bytes from anInputStreamto chars on aWriter. The platform's default encoding is used for the byte-to-char conversion.- Throws:
IOException
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copy
Copy and convert bytes from anInputStreamto chars on aWriter. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Copy and convert bytes from anInputStreamto chars on aWriter, using the specified encoding.- Parameters:
encoding- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
IOException
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copy
public static void copy(InputStream input, Writer output, String encoding, int bufferSize) throws IOException Copy and convert bytes from anInputStreamto chars on aWriter, using the specified encoding.- Parameters:
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.- Throws:
IOException
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toString
Get the contents of anInputStreamas a String. The platform's default encoding is used for the byte-to-char conversion.- Throws:
IOException
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toString
Get the contents of anInputStreamas a String. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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toString
Get the contents of anInputStreamas a String.- Parameters:
encoding- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
IOException
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toString
public static String toString(InputStream input, String encoding, int bufferSize) throws IOException Get the contents of anInputStreamas a String.- Parameters:
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.- Throws:
IOException
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toByteArray
Get the contents of anInputStreamas abyte[].- Throws:
IOException
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toByteArray
Get the contents of anInputStreamas abyte[].- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Serialize chars from aReaderto bytes on anOutputStream, and flush theOutputStream.- Throws:
IOException
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copy
Serialize chars from aReaderto bytes on anOutputStream, and flush theOutputStream.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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toString
Get the contents of aReaderas a String.- Throws:
IOException
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toString
Get the contents of aReaderas a String.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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toByteArray
Get the contents of aReaderas abyte[].- Throws:
IOException
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toByteArray
Get the contents of aReaderas abyte[].- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Serialize chars from aStringto bytes on anOutputStream, and flush theOutputStream.- Throws:
IOException
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copy
Serialize chars from aStringto bytes on anOutputStream, and flush theOutputStream.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Copy chars from aStringto aWriter.- Throws:
IOException
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bufferedCopy
Deprecated.Buffering streams is actively harmful! See the class description as to why. Usecopy(InputStream, OutputStream)instead.Copy bytes from anInputStreamto anOutputStream, with buffering. This is equivalent to passing aBufferedInputStreamandBufferedOutputStreamtocopy(InputStream, OutputStream), and flushing the output stream afterwards. The streams are not closed after the copy.- Throws:
IOException
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toByteArray
Get the contents of aStringas abyte[].- Throws:
IOException
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toByteArray
Get the contents of aStringas abyte[].- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Copy and convert bytes from abyte[]to chars on aWriter. The platform's default encoding is used for the byte-to-char conversion.- Throws:
IOException
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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:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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copy
Copy and convert bytes from abyte[]to chars on aWriter, using the specified encoding.- Parameters:
encoding- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
IOException
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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:
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.- Throws:
IOException
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toString
Get the contents of abyte[]as a String. The platform's default encoding is used for the byte-to-char conversion.- Throws:
IOException
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toString
Get the contents of abyte[]as a String. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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toString
Get the contents of abyte[]as a String.- Parameters:
encoding- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
IOException
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toString
Get the contents of abyte[]as a String.- Parameters:
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.- Throws:
IOException
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copy
Copy bytes from abyte[]to anOutputStream.- Throws:
IOException
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copy
Copy bytes from abyte[]to anOutputStream.- Parameters:
bufferSize- Size of internal buffer to use.- Throws:
IOException
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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
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close
Closes the input stream. The input stream can be null and any IOException's will be swallowed.- Parameters:
inputStream- The stream to close.
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close
Closes a channel. Channel can be null and any IOException's will be swallowed.- Parameters:
channel- The stream to close.
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close
Closes the output stream. The output stream can be null and any IOException's will be swallowed.- Parameters:
outputStream- The stream to close.
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close
Closes the reader. The reader can be null and any IOException's will be swallowed.- Parameters:
reader- The reader to close.
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close
Closes the writer. The writer can be null and any IOException's will be swallowed.- Parameters:
writer- The writer to close.
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