Java example source code file (ProgressMonitorInputStream.java)

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Java - Java tags/keywords

awt, filterinputstream, interruptedioexception, ioexception, object, progressmonitor, progressmonitorinputstream

The ProgressMonitorInputStream.java Java example source code

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */



package javax.swing;



import java.io.*;
import java.awt.Component;



/**
 * Monitors the progress of reading from some InputStream. This ProgressMonitor
 * is normally invoked in roughly this form:
 * <pre>
 * InputStream in = new BufferedInputStream(
 *                          new ProgressMonitorInputStream(
 *                                  parentComponent,
 *                                  "Reading " + fileName,
 *                                  new FileInputStream(fileName)));
 * </pre>

 * This creates a progress monitor to monitor the progress of reading
 * the input stream.  If it's taking a while, a ProgressDialog will
 * be popped up to inform the user.  If the user hits the Cancel button
 * an InterruptedIOException will be thrown on the next read.
 * All the right cleanup is done when the stream is closed.
 *
 *
 * <p>
 *
 * For further documentation and examples see
 * <a href="http://docs.oracle.com/javase/tutorial/uiswing/components/progress.html">How to Monitor Progress,
 * a section in <em>The Java Tutorial.
 *
 * @see ProgressMonitor
 * @see JOptionPane
 * @author James Gosling
 */
public class ProgressMonitorInputStream extends FilterInputStream
{
    private ProgressMonitor monitor;
    private int             nread = 0;
    private int             size = 0;


    /**
     * Constructs an object to monitor the progress of an input stream.
     *
     * @param message Descriptive text to be placed in the dialog box
     *                if one is popped up.
     * @param parentComponent The component triggering the operation
     *                        being monitored.
     * @param in The input stream to be monitored.
     */
    public ProgressMonitorInputStream(Component parentComponent,
                                      Object message,
                                      InputStream in) {
        super(in);
        try {
            size = in.available();
        }
        catch(IOException ioe) {
            size = 0;
        }
        monitor = new ProgressMonitor(parentComponent, message, null, 0, size);
    }


    /**
     * Get the ProgressMonitor object being used by this stream. Normally
     * this isn't needed unless you want to do something like change the
     * descriptive text partway through reading the file.
     * @return the ProgressMonitor object used by this object
     */
    public ProgressMonitor getProgressMonitor() {
        return monitor;
    }


    /**
     * Overrides <code>FilterInputStream.read
     * to update the progress monitor after the read.
     */
    public int read() throws IOException {
        int c = in.read();
        if (c >= 0) monitor.setProgress(++nread);
        if (monitor.isCanceled()) {
            InterruptedIOException exc =
                                    new InterruptedIOException("progress");
            exc.bytesTransferred = nread;
            throw exc;
        }
        return c;
    }


    /**
     * Overrides <code>FilterInputStream.read
     * to update the progress monitor after the read.
     */
    public int read(byte b[]) throws IOException {
        int nr = in.read(b);
        if (nr > 0) monitor.setProgress(nread += nr);
        if (monitor.isCanceled()) {
            InterruptedIOException exc =
                                    new InterruptedIOException("progress");
            exc.bytesTransferred = nread;
            throw exc;
        }
        return nr;
    }


    /**
     * Overrides <code>FilterInputStream.read
     * to update the progress monitor after the read.
     */
    public int read(byte b[],
                    int off,
                    int len) throws IOException {
        int nr = in.read(b, off, len);
        if (nr > 0) monitor.setProgress(nread += nr);
        if (monitor.isCanceled()) {
            InterruptedIOException exc =
                                    new InterruptedIOException("progress");
            exc.bytesTransferred = nread;
            throw exc;
        }
        return nr;
    }


    /**
     * Overrides <code>FilterInputStream.skip
     * to update the progress monitor after the skip.
     */
    public long skip(long n) throws IOException {
        long nr = in.skip(n);
        if (nr > 0) monitor.setProgress(nread += nr);
        return nr;
    }


    /**
     * Overrides <code>FilterInputStream.close
     * to close the progress monitor as well as the stream.
     */
    public void close() throws IOException {
        in.close();
        monitor.close();
    }


    /**
     * Overrides <code>FilterInputStream.reset
     * to reset the progress monitor as well as the stream.
     */
    public synchronized void reset() throws IOException {
        in.reset();
        nread = size - in.available();
        monitor.setProgress(nread);
    }
}