FileDocCategorySizeDatePackage
IOUtil.javaAPI DocApache James 2.3.126485Fri Jan 12 12:56:34 GMT 2007org.apache.james.util.io

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).

author
Peter Donald
author
Jeff Turner
version
CVS $Revision: 494012 $ $Date: 2007-01-08 11:23:58 +0100 (Mo, 08 Jan 2007) $
since
4.0

Fields Summary
private static final int
DEFAULT_BUFFER_SIZE
Constructors Summary
private IOUtil()
Private constructor to prevent instantiation.
Methods Summary
public static booleancontentEquals(java.io.InputStream input1, java.io.InputStream input2)
Compare the contents of two Streams to determine if they are equal or not.

param
input1 the first stream
param
input2 the second stream
return
true if the content of the streams are equal or they both don't exist, false otherwise

        final InputStream bufferedInput1 = new BufferedInputStream( input1 );
        final InputStream bufferedInput2 = new BufferedInputStream( input2 );

        int ch = bufferedInput1.read();
        while( -1 != ch )
        {
            final int ch2 = bufferedInput2.read();
            if( ch != ch2 )
            {
                return false;
            }
            ch = bufferedInput1.read();
        }

        final int ch2 = bufferedInput2.read();
        if( -1 != ch2 )
        {
            return false;
        }
        else
        {
            return true;
        }
public static voidcopy(java.io.InputStream input, java.io.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( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(java.io.InputStream input, java.io.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.

param
bufferSize Size of internal buffer to use.

        final InputStreamReader in = new InputStreamReader( input );
        copy( in, output, bufferSize );
public static voidcopy(java.io.InputStream input, java.io.Writer output, java.lang.String encoding)
Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.

        final InputStreamReader in = new InputStreamReader( input, encoding );
        copy( in, output );
public static voidcopy(java.io.InputStream input, java.io.Writer output, java.lang.String encoding, int bufferSize)
Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
param
bufferSize Size of internal buffer to use.

        final InputStreamReader in = new InputStreamReader( input, encoding );
        copy( in, output, bufferSize );
public static voidcopy(java.io.Reader input, java.io.OutputStream output)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

        copy( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(java.io.Reader input, java.io.OutputStream output, int bufferSize)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

param
bufferSize Size of internal buffer to use.

        final OutputStreamWriter out = new OutputStreamWriter( output );
        copy( input, out, bufferSize );
        // NOTE: Unless anyone is planning on rewriting OutputStreamWriter, we have to flush
        // here.
        out.flush();
public static voidcopy(java.lang.String input, java.io.OutputStream output)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

        copy( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(java.lang.String input, java.io.OutputStream output, int bufferSize)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

param
bufferSize Size of internal buffer to use.

        final StringReader in = new StringReader( input );
        final OutputStreamWriter out = new OutputStreamWriter( output );
        copy( in, out, bufferSize );
        // NOTE: Unless anyone is planning on rewriting OutputStreamWriter, we have to flush
        // here.
        out.flush();
public static voidcopy(java.lang.String input, java.io.Writer output)
Copy chars from a String to a Writer.

        output.write( input );
public static voidcopy(byte[] input, java.io.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( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(byte[] input, java.io.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.

param
bufferSize Size of internal buffer to use.

        final ByteArrayInputStream in = new ByteArrayInputStream( input );
        copy( in, output, bufferSize );
public static voidcopy(byte[] input, java.io.Writer output, java.lang.String encoding)
Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.

        final ByteArrayInputStream in = new ByteArrayInputStream( input );
        copy( in, output, encoding );
public static voidcopy(byte[] input, java.io.Writer output, java.lang.String encoding, int bufferSize)
Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
param
bufferSize Size of internal buffer to use.

        final ByteArrayInputStream in = new ByteArrayInputStream( input );
        copy( in, output, encoding, bufferSize );
public static voidcopy(byte[] input, java.io.OutputStream output)
Copy bytes from a byte[] to an OutputStream.

        copy( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(byte[] input, java.io.OutputStream output, int bufferSize)
Copy bytes from a byte[] to an OutputStream.

param
bufferSize Size of internal buffer to use.

        output.write( input );
public static voidcopy(java.io.InputStream input, java.io.OutputStream output)
Copy bytes from an InputStream to an OutputStream.

        copy( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(java.io.InputStream input, java.io.OutputStream output, int bufferSize)
Copy bytes from an InputStream to an OutputStream.

param
bufferSize Size of internal buffer to use.

        final byte[] buffer = new byte[ bufferSize ];
        int n = 0;
        while( -1 != ( n = input.read( buffer ) ) )
        {
            output.write( buffer, 0, n );
        }
public static voidcopy(java.io.Reader input, java.io.Writer output)
Copy chars from a Reader to a Writer.

        copy( input, output, DEFAULT_BUFFER_SIZE );
public static voidcopy(java.io.Reader input, java.io.Writer output, int bufferSize)
Copy chars from a Reader to a Writer.

param
bufferSize Size of internal buffer to use.

        final char[] buffer = new char[ bufferSize ];
        int n = 0;
        while( -1 != ( n = input.read( buffer ) ) )
        {
            output.write( buffer, 0, n );
        }
public static voidshutdownReader(java.io.Reader input)
Unconditionally close an Reader. Equivalent to {@link Reader#close()}, except any exceptions will be ignored.

param
input A (possibly null) Reader

        if( null == input )
        {
            return;
        }

        try
        {
            input.close();
        }
        catch( final IOException ioe )
        {
        }
public static voidshutdownStream(java.io.OutputStream output)
Unconditionally close an OutputStream. Equivalent to {@link OutputStream#close()}, except any exceptions will be ignored.

param
output A (possibly null) OutputStream

        if( null == output )
        {
            return;
        }

        try
        {
            output.close();
        }
        catch( final IOException ioe )
        {
        }
public static voidshutdownStream(java.io.InputStream input)
Unconditionally close an InputStream. Equivalent to {@link InputStream#close()}, except any exceptions will be ignored.

param
input A (possibly null) InputStream

        if( null == input )
        {
            return;
        }

        try
        {
            input.close();
        }
        catch( final IOException ioe )
        {
        }
public static voidshutdownWriter(java.io.Writer output)
Unconditionally close an Writer. Equivalent to {@link Writer#close()}, except any exceptions will be ignored.

param
output A (possibly null) Writer

        if( null == output )
        {
            return;
        }

        try
        {
            output.close();
        }
        catch( final IOException ioe )
        {
        }
public static byte[]toByteArray(java.io.InputStream input)
Get the contents of an InputStream as a byte[].

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

param
bufferSize Size of internal buffer to use.

        final ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy( input, output, bufferSize );
        return output.toByteArray();
public static byte[]toByteArray(java.io.Reader input)
Get the contents of a Reader as a byte[].

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

param
bufferSize Size of internal buffer to use.

        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy( input, output, bufferSize );
        return output.toByteArray();
public static byte[]toByteArray(java.lang.String input)
Get the contents of a String as a byte[].

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

param
bufferSize Size of internal buffer to use.

        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy( input, output, bufferSize );
        return output.toByteArray();
public static java.lang.StringtoString(java.io.InputStream input)
Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.

        return toString( input, DEFAULT_BUFFER_SIZE );
public static java.lang.StringtoString(java.io.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.

param
bufferSize Size of internal buffer to use.

        final StringWriter sw = new StringWriter();
        copy( input, sw, bufferSize );
        return sw.toString();
public static java.lang.StringtoString(java.io.InputStream input, java.lang.String encoding)
Get the contents of an InputStream as a String.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.

        return toString( input, encoding, DEFAULT_BUFFER_SIZE );
public static java.lang.StringtoString(java.io.InputStream input, java.lang.String encoding, int bufferSize)
Get the contents of an InputStream as a String.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
param
bufferSize Size of internal buffer to use.

        final StringWriter sw = new StringWriter();
        copy( input, sw, encoding, bufferSize );
        return sw.toString();
public static java.lang.StringtoString(java.io.Reader input)
Get the contents of a Reader as a String.

        return toString( input, DEFAULT_BUFFER_SIZE );
public static java.lang.StringtoString(java.io.Reader input, int bufferSize)
Get the contents of a Reader as a String.

param
bufferSize Size of internal buffer to use.

        final StringWriter sw = new StringWriter();
        copy( input, sw, bufferSize );
        return sw.toString();
public static java.lang.StringtoString(byte[] input)
Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.

        return toString( input, DEFAULT_BUFFER_SIZE );
public static java.lang.StringtoString(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.

param
bufferSize Size of internal buffer to use.

        final StringWriter sw = new StringWriter();
        copy( input, sw, bufferSize );
        return sw.toString();
public static java.lang.StringtoString(byte[] input, java.lang.String encoding)
Get the contents of a byte[] as a String.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.

        return toString( input, encoding, DEFAULT_BUFFER_SIZE );
public static java.lang.StringtoString(byte[] input, java.lang.String encoding, int bufferSize)
Get the contents of a byte[] as a String.

param
encoding The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
param
bufferSize Size of internal buffer to use.

        final StringWriter sw = new StringWriter();
        copy( input, sw, encoding, bufferSize );
        return sw.toString();