org.codehaus.plexus.util

Class IOUtil

public final class IOUtil extends Object

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 {@link 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 {@link 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: CVS $Revision: 1106 $ $Date: 2004-10-07 21:29:57 +0200 (Thu, 07 Oct 2004) $

Author: Peter Donald Jeff Turner

Field Summary
static intDEFAULT_BUFFER_SIZE
Constructor Summary
IOUtil()
Private constructor to prevent instantiation.
Method Summary
static voidbufferedCopy(InputStream input, OutputStream output)
Copy bytes from an InputStream to an OutputStream, with buffering.
static voidclose(InputStream inputStream)
Closes the input stream.
static voidclose(OutputStream outputStream)
Closes the output stream.
static voidclose(Reader reader)
Closes the reader.
static voidclose(Writer writer)
Closes the writer.
static booleancontentEquals(InputStream input1, InputStream input2)
Compare the contents of two Streams to determine if they are equal or not.
static voidcopy(InputStream input, OutputStream output)
Copy bytes from an InputStream to an OutputStream.
static voidcopy(InputStream input, OutputStream output, int bufferSize)
Copy bytes from an InputStream to an OutputStream.
static voidcopy(Reader input, Writer output)
Copy chars from a Reader to a Writer.
static voidcopy(Reader input, Writer output, int bufferSize)
Copy chars from a Reader to a Writer.
static voidcopy(InputStream input, Writer output)
Copy and convert bytes from an InputStream to chars on a Writer.
static voidcopy(InputStream input, Writer output, int bufferSize)
Copy and convert bytes from an InputStream to chars on a Writer.
static voidcopy(InputStream input, Writer output, String encoding)
Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
static voidcopy(InputStream input, Writer output, String encoding, int bufferSize)
Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
static voidcopy(Reader input, OutputStream output)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
static voidcopy(Reader input, OutputStream output, int bufferSize)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
static voidcopy(String input, OutputStream output)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
static voidcopy(String input, OutputStream output, int bufferSize)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
static voidcopy(String input, Writer output)
Copy chars from a String to a Writer.
static voidcopy(byte[] input, Writer output)
Copy and convert bytes from a byte[] to chars on a Writer.
static voidcopy(byte[] input, Writer output, int bufferSize)
Copy and convert bytes from a byte[] to chars on a Writer.
static voidcopy(byte[] input, Writer output, String encoding)
Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.
static voidcopy(byte[] input, Writer output, String encoding, int bufferSize)
Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.
static voidcopy(byte[] input, OutputStream output)
Copy bytes from a byte[] to an OutputStream.
static voidcopy(byte[] input, OutputStream output, int bufferSize)
Copy bytes from a byte[] to an OutputStream.
static byte[]toByteArray(InputStream input)
Get the contents of an InputStream as a byte[].
static byte[]toByteArray(InputStream input, int bufferSize)
Get the contents of an InputStream as a byte[].
static byte[]toByteArray(Reader input)
Get the contents of a Reader as a byte[].
static byte[]toByteArray(Reader input, int bufferSize)
Get the contents of a Reader as a byte[].
static byte[]toByteArray(String input)
Get the contents of a String as a byte[].
static byte[]toByteArray(String input, int bufferSize)
Get the contents of a String as a byte[].
static StringtoString(InputStream input)
Get the contents of an InputStream as a String.
static StringtoString(InputStream input, int bufferSize)
Get the contents of an InputStream as a String.
static StringtoString(InputStream input, String encoding)
Get the contents of an InputStream as a String.
static StringtoString(InputStream input, String encoding, int bufferSize)
Get the contents of an InputStream as a String.
static StringtoString(Reader input)
Get the contents of a Reader as a String.
static StringtoString(Reader input, int bufferSize)
Get the contents of a Reader as a String.
static StringtoString(byte[] input)
Get the contents of a byte[] as a String.
static StringtoString(byte[] input, int bufferSize)
Get the contents of a byte[] as a String.
static StringtoString(byte[] input, String encoding)
Get the contents of a byte[] as a String.
static StringtoString(byte[] input, String encoding, int bufferSize)
Get the contents of a byte[] as a String.

Field Detail

DEFAULT_BUFFER_SIZE

private static final int DEFAULT_BUFFER_SIZE

Constructor Detail

IOUtil

private IOUtil()
Private constructor to prevent instantiation.

Method Detail

bufferedCopy

public static void bufferedCopy(InputStream input, OutputStream output)

Deprecated: Buffering streams is actively harmful! See the class description as to why. Use {@link #copy(InputStream, OutputStream)} instead.

Copy bytes from an InputStream to an OutputStream, with buffering. This is equivalent to passing a {@link java.io.BufferedInputStream} and {@link java.io.BufferedOutputStream} to {@link #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.

Parameters: 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.

Parameters: 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.

Parameters: 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.

Parameters: wrtier The writer to close.

contentEquals

public static boolean contentEquals(InputStream input1, InputStream input2)
Compare the contents of two Streams to determine if they are equal or not.

Parameters: input1 the first stream input2 the second stream

Returns: 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)
Copy bytes from an InputStream to an OutputStream.

copy

public static void copy(InputStream input, OutputStream output, int bufferSize)
Copy bytes from an InputStream to an OutputStream.

Parameters: bufferSize Size of internal buffer to use.

copy

public static void copy(Reader input, Writer output)
Copy chars from a Reader to a Writer.

copy

public static void copy(Reader input, Writer output, int bufferSize)
Copy chars from a Reader to a Writer.

Parameters: bufferSize Size of internal buffer to use.

copy

public static void copy(InputStream input, Writer output)
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, int bufferSize)
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.

Parameters: bufferSize Size of internal buffer to use.

copy

public 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.

Parameters: 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)
Copy and convert bytes from an InputStream to chars on a Writer, 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.

copy

public static void copy(Reader input, OutputStream output)
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)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

Parameters: bufferSize Size of internal buffer to use.

copy

public static void copy(String input, OutputStream output)
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)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

Parameters: bufferSize Size of internal buffer to use.

copy

public static void copy(String input, Writer output)
Copy chars from a String to a Writer.

copy

public static void copy(byte[] input, Writer output)
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, int bufferSize)
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.

Parameters: bufferSize Size of internal buffer to use.

copy

public 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.

Parameters: 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)
Copy and convert bytes from a byte[] to chars on a Writer, 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.

copy

public static void copy(byte[] input, OutputStream output)
Copy bytes from a byte[] to an OutputStream.

copy

public static void copy(byte[] input, OutputStream output, int bufferSize)
Copy bytes from a byte[] to an OutputStream.

Parameters: bufferSize Size of internal buffer to use.

toByteArray

public static byte[] toByteArray(InputStream input)
Get the contents of an InputStream as a byte[].

toByteArray

public static byte[] toByteArray(InputStream input, int bufferSize)
Get the contents of an InputStream as a byte[].

Parameters: bufferSize Size of internal buffer to use.

toByteArray

public static byte[] toByteArray(Reader input)
Get the contents of a Reader as a byte[].

toByteArray

public static byte[] toByteArray(Reader input, int bufferSize)
Get the contents of a Reader as a byte[].

Parameters: bufferSize Size of internal buffer to use.

toByteArray

public static byte[] toByteArray(String input)
Get the contents of a String as a byte[].

toByteArray

public static byte[] toByteArray(String input, int bufferSize)
Get the contents of a String as a byte[].

Parameters: bufferSize Size of internal buffer to use.

toString

public static String toString(InputStream input)
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, int bufferSize)
Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.

Parameters: bufferSize Size of internal buffer to use.

toString

public static String toString(InputStream input, String encoding)
Get the contents of an InputStream as a String.

Parameters: 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)
Get the contents of an InputStream 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.

toString

public static String toString(Reader input)
Get the contents of a Reader as a String.

toString

public static String toString(Reader input, int bufferSize)
Get the contents of a Reader as a String.

Parameters: bufferSize Size of internal buffer to use.

toString

public static String toString(byte[] input)
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, int bufferSize)
Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.

Parameters: bufferSize Size of internal buffer to use.

toString

public static String toString(byte[] input, String encoding)
Get the contents of a byte[] as a String.

Parameters: 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)
Get the contents of a byte[] 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.