Java InputStream to OutputStream copyStream(InputStream in, OutputStream out)

Description

Copies data from an InputStream to an OutputStream.

License

Open Source License

Parameter

Parameter	Description
in	the stream to read from
out	the stream to write to

Exception

Parameter	Description
NullPointerException	if either in or out are null
IOException	if an I/O error occurs

Return

the number of bytes read from the input stream

Declaration

public static long copyStream(InputStream in, OutputStream out) throws IOException 

Method Source Code

//package com.java2s;
/*/*from  w  ww .j av a 2  s  .c  om*/
 * $Id$
 *
 * Copyright (C) 2003-2015 JNode.org
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

import java.io.Flushable;
import java.io.InputStream;

import java.io.IOException;
import java.io.OutputStream;

public class Main {
    private static final int BUFFER_SIZE = 4096;
    private static final String ex_null_param = "A required paramater is null";

    /**
     * Copies data from an InputStream to an OutputStream.
     *
     * This method allocates a 4096 byte buffer each time it is called.
     *
     * At the end of writing, the OutputStream will be flushed, but no streams will be closed.
     *
     * @param in the stream to read from
     * @param out the stream to write to
     * @return the number of bytes read from the input stream
     * @throws NullPointerException if either in or out are null
     * @throws IOException if an I/O error occurs
     */
    public static long copyStream(InputStream in, OutputStream out) throws IOException {
        return copyStream(in, out, new byte[BUFFER_SIZE]);
    }

    /**
     * Copies data from an InputStream to an OutputStream.
     *
     * This method allocates a buffer of 'bufferSize' when it is called.
     *
     * At the end of writing, the OutputStream will be flushed, but no streams will be closed.
     *
     * @param in the stream to read from
     * @param out the stream to write to
     * @param bufferSize the size of buffer to use for the copy
     * @return the number of bytes read from the input stream
     * @throws NullPointerException if either in or out are null
     * @throws IOException if an I/O error occurs
     */
    public static long copyStream(InputStream in, OutputStream out, int bufferSize) throws IOException {
        return copyStream(in, out, new byte[bufferSize]);
    }

    /**
     * Copies data from an InputStream to an OutputStream
     *
     * If copying multiple streams, this method may be prefered to the others
     * as a way to use the same buffer instead of allocating a new buffer on each call.
     *
     * At the end of writing, the OutputStream will be flushed, but no streams will be closed.
     *
     * @param in the stream to read from
     * @param out the stream to write to
     * @param buffer a pre-allocated buffer to use.
     * @return the number of bytes read from the input stream
     * @throws NullPointerException if either in, out or buffer are null
     * @throws IOException if an I/O error occurs
     */
    public static long copyStream(InputStream in, OutputStream out, byte[] buffer) throws IOException {
        checkNull(in, out, buffer);

        long totalBytes = 0;
        int len = 0;
        while ((len = in.read(buffer)) > 0) {
            out.write(buffer, 0, len);
            totalBytes += len;
        }
        out.flush();
        return totalBytes;
    }

    /**
     * Check for null objects in a list of objects.
     */
    private static void checkNull(Object... objs) {
        for (Object obj : objs) {
            if (obj == null)
                throw new NullPointerException(ex_null_param);
        }
    }

    /**
     * Call the flush method of a list of Flushable objects.
     *
     * This method will not throw a NullPointerException if any of the objects are null.
     *
     * This method will trap the IOException from flush.
     *
     * @param objs one or more Flushable objects
     */
    public static void flush(Flushable... objs) {
        for (Flushable obj : objs) {
            if (obj != null) {
                try {
                    obj.flush();
                } catch (IOException e) {
                    // ignore
                }
            }
        }
    }
}

Related

1. copyStream(InputStream in, OutputStream os)
2. copyStream(InputStream in, OutputStream os)
3. copyStream(InputStream in, OutputStream out)
4. copyStream(InputStream in, OutputStream out)
5. copyStream(InputStream in, OutputStream out)
6. copyStream(InputStream in, OutputStream out)
7. copyStream(InputStream in, OutputStream out)
8. copyStream(InputStream in, OutputStream out)
9. copyStream(InputStream in, OutputStream out)