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Commons IO example source code file (CopyUtils.java)

This example Commons IO source code file (CopyUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons IO tags/keywords

bytearrayinputstream, bytearrayinputstream, copyutils, inputstream, inputstreamreader, io, ioexception, ioexception, outputstream, outputstreamwriter, outputstreamwriter, string, stringreader, writer, writer

The Commons IO CopyUtils.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.io;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.Writer;

/**
 * This class provides static utility methods for buffered
 * copying between sources (<code>InputStream, Reader,
 * <code>String and byte[]) and destinations
 * (<code>OutputStream, Writer, String and
 * <code>byte[]).
 * <p>
 * Unless otherwise noted, these <code>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' <code>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
 * <a href="http://www.unixreview.com/articles/1998/9804/9804ja/ja.htm">this
 * UnixReview article</a>.
 * <p>
 * For byte-to-char methods, a <code>copy variant allows the encoding
 * to be selected (otherwise the platform default is used). We would like to
 * encourage you to always specify the encoding because relying on the platform
 * default can lead to unexpected results.
 * <p
 * We don't provide special variants for the <code>copy methods that
 * let you specify the buffer size because in modern VMs the impact on speed
 * seems to be minimal. We're using a default buffer size of 4 KB.
 * <p>
 * The <code>copy methods use an internal buffer when copying. It is
 * therefore advisable <em>not to deliberately wrap the stream arguments
 * to the <code>copy methods in Buffered* streams. For
 * example, don't do the following:
 * <pre>
 *  copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );
 *  </pre>
 * The rationale is as follows:
 * <p>
 * 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
 * <code>read requests can inexpensively get their data (until the buffer
 * runs out).
 * <p>
 * However, the <code>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).
 * <p>
 * Behold, intrepid explorers; a map of this class:
 * <pre>
 *       Method      Input               Output          Dependency
 *       ------      -----               ------          -------
 * 1     copy        InputStream         OutputStream    (primitive)
 * 2     copy        Reader              Writer          (primitive)
 *
 * 3     copy        InputStream         Writer          2
 *
 * 4     copy        Reader              OutputStream    2
 *
 * 5     copy        String              OutputStream    2
 * 6     copy        String              Writer          (trivial)
 *
 * 7     copy        byte[]              Writer          3
 * 8     copy        byte[]              OutputStream    (trivial)
 * </pre>
 * <p>
 * Note that only the first two methods shuffle bytes; the rest use these
 * two, or (if possible) copy using native Java copy methods. As there are
 * method variants to specify the encoding, each row may
 * correspond to up to 2 methods.
 * <p>
 * Origin of code: Excalibur.
 *
 * @author Peter Donald
 * @author Jeff Turner
 * @author Matthew Hawthorne
 * @version $Id: CopyUtils.java 659817 2008-05-24 13:23:10Z niallp $
 * @deprecated Use IOUtils. Will be removed in 2.0.
 *  Methods renamed to IOUtils.write() or IOUtils.copy().
 *  Null handling behaviour changed in IOUtils (null data does not
 *  throw NullPointerException).
 */
@Deprecated
public class CopyUtils {

    /**
     * The default size of the buffer.
     */
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * Instances should NOT be constructed in standard programming.
     */
    public CopyUtils() { }

    // ----------------------------------------------------------------
    // byte[] -> OutputStream
    // ----------------------------------------------------------------

    /**
     * Copy bytes from a <code>byte[] to an OutputStream.
     * @param input the byte array to read from
     * @param output the <code>OutputStream to write to
     * @throws IOException In case of an I/O problem
     */
    public static void copy(byte[] input, OutputStream output)
            throws IOException {
        output.write(input);
    }

    // ----------------------------------------------------------------
    // byte[] -> Writer
    // ----------------------------------------------------------------

    /**
     * Copy and convert bytes from a <code>byte[] to chars on a
     * <code>Writer.
     * The platform's default encoding is used for the byte-to-char conversion.
     * @param input the byte array to read from
     * @param output the <code>Writer to write to
     * @throws IOException In case of an I/O problem
     */
    public static void copy(byte[] input, Writer output)
            throws IOException {
        ByteArrayInputStream in = new ByteArrayInputStream(input);
        copy(in, output);
    }


    /**
     * Copy and convert bytes from a <code>byte[] to chars on a
     * <code>Writer, using the specified encoding.
     * @param input the byte array to read from
     * @param output the <code>Writer to write to
     * @param encoding The name of a supported character encoding. See the
     * <a href="http://www.iana.org/assignments/character-sets">IANA
     * Charset Registry</a> for a list of valid encoding types.
     * @throws IOException In case of an I/O problem
     */
    public static void copy(
            byte[] input,
            Writer output,
            String encoding)
                throws IOException {
        ByteArrayInputStream in = new ByteArrayInputStream(input);
        copy(in, output, encoding);
    }


    // ----------------------------------------------------------------
    // Core copy methods
    // ----------------------------------------------------------------

    /**
     * Copy bytes from an <code>InputStream to an
     * <code>OutputStream.
     * @param input the <code>InputStream to read from
     * @param output the <code>OutputStream to write to
     * @return the number of bytes copied
     * @throws IOException In case of an I/O problem
     */
    public static int copy(
            InputStream input,
            OutputStream output)
                throws IOException {
        byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
        int count = 0;
        int n = 0;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return count;
    }

    // ----------------------------------------------------------------
    // Reader -> Writer
    // ----------------------------------------------------------------

    /**
     * Copy chars from a <code>Reader to a Writer.
     * @param input the <code>Reader to read from
     * @param output the <code>Writer to write to
     * @return the number of characters copied
     * @throws IOException In case of an I/O problem
     */
    public static int copy(
            Reader input,
            Writer output)
                throws IOException {
        char[] buffer = new char[DEFAULT_BUFFER_SIZE];
        int count = 0;
        int n = 0;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return count;
    }

    // ----------------------------------------------------------------
    // InputStream -> Writer
    // ----------------------------------------------------------------

    /**
     * Copy and convert bytes from an <code>InputStream to chars on a
     * <code>Writer.
     * The platform's default encoding is used for the byte-to-char conversion.
     * @param input the <code>InputStream to read from
     * @param output the <code>Writer to write to
     * @throws IOException In case of an I/O problem
     */
    public static void copy(
            InputStream input,
            Writer output)
                throws IOException {
        InputStreamReader in = new InputStreamReader(input);
        copy(in, output);
    }

    /**
     * Copy and convert bytes from an <code>InputStream to chars on a
     * <code>Writer, using the specified encoding.
     * @param input the <code>InputStream to read from
     * @param output the <code>Writer to write to
     * @param encoding The name of a supported character encoding. See the
     * <a href="http://www.iana.org/assignments/character-sets">IANA
     * Charset Registry</a> for a list of valid encoding types.
     * @throws IOException In case of an I/O problem
     */
    public static void copy(
            InputStream input,
            Writer output,
            String encoding)
                throws IOException {
        InputStreamReader in = new InputStreamReader(input, encoding);
        copy(in, output);
    }


    // ----------------------------------------------------------------
    // Reader -> OutputStream
    // ----------------------------------------------------------------

    /**
     * Serialize chars from a <code>Reader to bytes on an
     * <code>OutputStream, and flush the OutputStream.
     * @param input the <code>Reader to read from
     * @param output the <code>OutputStream to write to
     * @throws IOException In case of an I/O problem
     */
    public static void copy(
            Reader input,
            OutputStream output)
                throws IOException {
        OutputStreamWriter out = new OutputStreamWriter(output);
        copy(input, out);
        // XXX Unless anyone is planning on rewriting OutputStreamWriter, we
        // have to flush here.
        out.flush();
    }

    // ----------------------------------------------------------------
    // String -> OutputStream
    // ----------------------------------------------------------------

    /**
     * Serialize chars from a <code>String to bytes on an
     * <code>OutputStream, and
     * flush the <code>OutputStream.
     * @param input the <code>String to read from
     * @param output the <code>OutputStream to write to
     * @throws IOException In case of an I/O problem
     */
    public static void copy(
            String input,
            OutputStream output)
                throws IOException {
        StringReader in = new StringReader(input);
        OutputStreamWriter out = new OutputStreamWriter(output);
        copy(in, out);
        // XXX Unless anyone is planning on rewriting OutputStreamWriter, we
        // have to flush here.
        out.flush();
    }

    // ----------------------------------------------------------------
    // String -> Writer
    // ----------------------------------------------------------------

    /**
     * Copy chars from a <code>String to a Writer.
     * @param input the <code>String to read from
     * @param output the <code>Writer to write to
     * @throws IOException In case of an I/O problem
     */
    public static void copy(String input, Writer output)
                throws IOException {
        output.write(input);
    }

}

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