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How to use ProgressMonitorInputStream

I know I must be missing something very obvious, but whenever I try to use the ProgressMonitorInputStream when copying a file, I never get the ProgressDialog popup.
The examples I see don't seem to do much other than wrap their input stream within the ProgressMonitorInputStream.
The docs say:
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.
Here is an extremely simple example I put together that never pops up the dialog with a large file even if I setMillisToPopup() to an insanely small number.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingWorker;
public class ProgressBarDemo extends JFrame {
private static final long serialVersionUID = 1L;
private JButton button;
ProgressBarDemo()
{
button = new JButton("Click me!");
ButtonActionListener bal = new ButtonActionListener();
button.addActionListener(bal);
this.getContentPane().add(button);
}
private class ButtonActionListener implements ActionListener
{
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
Worker worker = new Worker();
worker.execute();
button.setEnabled(false);
}
}
public void go() {
this.setLocationRelativeTo(null);
this.setVisible(true);
this.pack();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private class Worker extends SwingWorker<Void, Void>
{
private void copyFile() {
File file = new File("/Users/mypath/Desktop/WirelessDiagnostics.tar.gz");
BufferedInputStream bis;
BufferedOutputStream baos;
try {
bis = new BufferedInputStream(new FileInputStream(file));
ProgressMonitorInputStream pmis = new ProgressMonitorInputStream(
ProgressBarDemo.this,
"Reading... " + file.getAbsolutePath(),
bis);
pmis.getProgressMonitor().setMillisToPopup(10);
baos = new BufferedOutputStream(new FileOutputStream("/Users/mypath/Desktop/NewWirelessDiagnostics.tar.gz"));
byte[] buffer = new byte[2048];
int nRead = 0;
while((nRead = pmis.read(buffer)) != -1) {
baos.write(buffer, 0, nRead);
}
pmis.close();
baos.flush();
baos.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
#Override
protected Void doInBackground() throws Exception {
// TODO Auto-generated method stub
copyFile();
return null;
}
#Override
protected void done() {
button.setEnabled(true);
}
}
}
public class TestProj {
public static void main(String[] args) {
ProgressBarDemo demo = new ProgressBarDemo();
demo.go();
}
}
Any suggestions?

You are calling copyFile from within the context of the Event Dispatching Thread, this means the EDT is unable to respond to new events or paint requests until after the method returns.
Try placing the call within it's own Thread context...
Thread t = new Thread(new Runnable(
public void run() {
copyFile();
}
));
t.start();
Equally, you could use a SwingWorker, it's a little bit of overkill, but you get the benefit of the PropertyChangeListener or it's done method, which could be used to re-enable the JButton, should you want to prevent people from clicking the button while a copy operation is in progress
See Concurrency in Swing and Worker Threads and SwingWorker for more details
Updated with example
Copying a 371mb file, across the local disk...
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingWorker;
public class ProgressBarDemo extends JFrame {
private static final long serialVersionUID = 1L;
private JButton button;
ProgressBarDemo() {
button = new JButton("Click me!");
ButtonActionListener bal = new ButtonActionListener();
button.addActionListener(bal);
this.getContentPane().add(button);
}
public void go() {
this.setLocationRelativeTo(null);
this.setVisible(true);
this.pack();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private void copyFile() {
File file = new File("...");
BufferedInputStream bis;
BufferedOutputStream baos;
try {
bis = new BufferedInputStream(new FileInputStream(file));
ProgressMonitorInputStream pmis = new ProgressMonitorInputStream(
this,
"Reading... " + file.getAbsolutePath(),
bis);
pmis.getProgressMonitor().setMillisToPopup(10);
baos = new BufferedOutputStream(new FileOutputStream("..."));
byte[] buffer = new byte[2048];
int nRead = 0;
while ((nRead = pmis.read(buffer)) != -1) {
baos.write(buffer, 0, nRead);
}
pmis.close();
baos.flush();
baos.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private class ButtonActionListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
button.setEnabled(false);
SwingWorker worker = new SwingWorker() {
#Override
protected Object doInBackground() throws Exception {
copyFile();
return null;
}
#Override
protected void done() {
button.setEnabled(true);
}
};
worker.execute();
}
}
public static void main(String[] args) {
ProgressBarDemo demo = new ProgressBarDemo();
demo.go();
}
}
Remember, there is overhead involved in setting up the window and displaying, which needs to be factored in. The system may "want" to display a window, but by the time the system has set it up and is prepared to display it, the steam may have finished copying...
Extended Example
nb: I don't really like the ProgressMonitor API as I've not been able to find where the UI is synchronised with the EDT, this can cause issues in Java 7 & 8
You could formalise the idea into a self contained worker, for example...
public class CopyWorker extends SwingWorker {
private File source;
private File dest;
private Component parent;
private ProgressMonitorInputStream pmis;
public CopyWorker(Component parent, File source, File dest) {
this.parent = parent;
this.source = source;
this.dest = dest;
}
#Override
protected Object doInBackground() throws Exception {
try (InputStream is = new FileInputStream(source)) {
try (OutputStream os = new FileOutputStream(dest)) {
pmis = new ProgressMonitorInputStream(
parent,
"Copying...",
is);
pmis.getProgressMonitor().setMillisToPopup(10);
byte[] buffer = new byte[2048];
int nRead = 0;
while ((nRead = pmis.read(buffer)) != -1) {
os.write(buffer, 0, nRead);
}
}
}
return null;
}
#Override
protected void done() {
try {
pmis.close();
} catch (Exception e) {
}
}
}
This attempts to contain the functionality, but also deals with the cleanup of the ProgressMonitorInputStream within the done method, making sure that it's done within the EDT. I'd personally attach a PropertyChangeListener to it and monitor the done property to determine when the worker has completed and examine the return result in order to pick up any exceptions, this gives you the ability to handle the exceptions in your own way and de-couples the worker from your process

Your program works on files, but when it comes to server and client streams, it
fails.
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.Socket;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JProgressBar;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingWorker;
public class FileReceive extends JFrame {
private static final long serialVersionUID = 1L;
private BufferedInputStream bufferInput;
private FileOutputStream fout;
private BufferedOutputStream bufferOutput;
private Socket client;
private JButton button;
private File fileinfo;
ProgressMonitorInputStream pois;
FileReceive() {
setLocationRelativeTo(null);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
receiveFile();
}
public static void main(String arg[]) {
new FileReceive();
}
public void receiveFile() {
try {
fileinfo=new File(filepath);
client=new Socket("localhost",9090);
fout=new FileOutputStream(fileinfo);
bufferOutput=new BufferedOutputStream(fout);
bufferInput=new BufferedInputStream(client.getInputStream());
pois=new ProgressMonitorInputStream(this, "reading", bufferInput);
int ch;
byte[] b=new byte[2048];
System.out.println("Receiving File");
while(-1!=(ch=pois.read(b))) {
bufferOutput.write(b,0,ch);
}
pois.close();
bufferInput.close();
bufferOutput.close();
fout.close();
client.close();
} catch (IOException e) {
JOptionPane.showMessageDialog(null, e.getMessage());
}
}
}

Progressbar of a bin file loading

how can I show a JProgressBar component like on the loading of a bin file?
I can only found solutions for iterative bin read and I'm using an object reading like:
CustomObj test = (CustomObj) in.readObject();
Cheers

If you can't measure the progress of the process, then you can only specify the "indeterminate mode" of the progress bar. When in this mode, the progress bar will indicate that it is working, but the completion of the process is unknown.
JProgressBar progress = new JProgressBar();
progress.setIndeterminate(true);

I recommend to do two things:
Creating a wrapping class around your original inputstream so that you can monitor the bytes that are read from it. Basically, you extends InputStream and delegate everything to the original stream (except a few methods) and in the read() method, you make sure that you notify some listener.
I guess that if you want a progress bar, it means that the loading operation takes a while and you want to provide feedback to the user. Long running task cannot run directly on the EDT (so typically, you cannot perform your task in an actionPerformed method). You therefore need to delegate the work to another Thread, by using a SwingWorker for example. If you don't this, then the UI will freeze and the feedback will not be viewable by the user.
This being, said it may seem complex or not trivial. Therefore, here some short example, that illustrates all this and works:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class TestProgressBar {
// Some simple listener interface to get a callback as bytes are being read
public static interface ProgressListener {
public void notifyByteRead();
}
// The wrapping input stream that will call the listener as bytes are being read
public static class ProgressInputStream extends InputStream {
private InputStream in;
#Override
public int read() throws IOException {
int read = in.read();
if (read > -1) {
// Here we notify the listener
listener.notifyByteRead();
}
return read;
}
#Override
public long skip(long n) throws IOException {
return in.skip(n);
}
#Override
public int available() throws IOException {
return in.available();
}
#Override
public void close() throws IOException {
in.close();
}
#Override
public void mark(int readlimit) {
in.mark(readlimit);
}
#Override
public void reset() throws IOException {
in.reset();
}
#Override
public boolean markSupported() {
return in.markSupported();
}
private ProgressListener listener;
public ProgressInputStream(InputStream in, ProgressListener listener) {
this.in = in;
this.listener = listener;
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
init();
}
});
}
public static void init() {
// 1. Let's create a big object with lots of data
List<Long> object = new ArrayList<Long>();
Random random = new Random();
for (int i = 0; i < 1e6; i++) {
object.add(random.nextLong());
}
// 2. We write it to a temp file
File tempFile = null;
ObjectOutputStream oos = null;
try {
tempFile = File.createTempFile("Test", ".bin");
tempFile.deleteOnExit();
FileOutputStream fos = new FileOutputStream(tempFile);
oos = new ObjectOutputStream(new BufferedOutputStream(fos));
oos.writeObject(object);
} catch (FileNotFoundException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
} finally {
try {
if (oos != null) {
oos.close();
}
} catch (IOException e1) {
e1.printStackTrace();
}
}
if (tempFile == null) {
System.exit(1);
}
// 3. Now let's build a UI to load that
final File theFile = tempFile;
JFrame frame = new JFrame("Test ghost text");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel(new BorderLayout());
final JProgressBar bar = new JProgressBar(0, (int) tempFile.length());
JButton button = new JButton("load");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
bar.setValue(0);
// Declare and implement a Swing worker that will run in another thread
SwingWorker<Void, Integer> worker = new SwingWorker<Void, Integer>() {
#Override
protected void process(List<Integer> chunks) {
// Here we are on the EDT, so we can safely notify the progressbar
super.process(chunks);
bar.setValue(bar.getValue() + chunks.size());
}
#Override
protected Void doInBackground() throws Exception {
// Here we are not in the EDT, we perform the task but don't modify anything in the UI
ProgressInputStream pis = new ProgressInputStream(new BufferedInputStream(new FileInputStream(theFile)),
new ProgressListener() {
#Override
public void notifyByteRead() {
publish(1); // the value that is sent here could be anything, we don't use it.
}
});
ObjectInputStream ois = new ObjectInputStream(pis);
try {
List<Long> readObject = (List<Long>) ois.readObject();
System.err.println("Loaded " + readObject.size() + " long values");
} catch (Exception e) {
e.printStackTrace();
} finally {
pis.close();
}
return null;
}
};
// Start the worker
worker.execute();
}
});
panel.add(bar);
panel.add(button, BorderLayout.EAST);
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
}

Subclass java.io.FilteredInputStream to count the number of bytes being read and insert it between your ObjectInputStream and the underlying InputStream being read.
You can update the progress bar by sampling the running count or using a callback built in to your subclass.
Example:
public class CountingInputStream extends FilteredInputStream {
private int numBytes;
public CountingInputStream(InputStream inputStream){
this(inputStream);
}
public int getNumBytes(){
return numBytes;
}
#Override
public int read() {
int b = super.read();
if(b != -1){
countBytes(1);
}
return b;
}
#Override
public int read(byte[] b){
int n = super.read(b);
if(n >= 0){
countBytes(n);
}
return n;
}
#Override
public int read(byte[] b, int off, int len){
int n = super.read(b, off, len);
if(n >= 0){
countBytes(n);
}
return n;
}
private void countBytes(int n){
numBytes += n;
}
}
It could be used like below (assume InputStream is your source of data).:
InputStream is = ...;
CountingInputStream cis = new CountingInputStream(is)
ObjectInputStream ois = new ObjectInputStream(cis);
ois.readObject();
You can sample cis.getNumBytes() from a different thread (potentially with a Swing timer) and use the returned value to update a JProgressBar

Downloading file/files in Java. Multithreading, this works?

First, everyone needs to know i'm relatively new to Java coding. To be more precise i'm completely new to Object Oriented Programming.
To the question.
I am trying to create a download class that updates a progress bar it was given to show its progress. And possibly anything else I decide to give it in the future to update.
The issue currently is that, in my head, this shouldn't work. I can do anything i want on the "main" method and the GUI is still responsive and quick. In my experience in past programming, this is not possible unless i thread the GUI. Why is this?
Since it works, is this ok to do it this way?
Class Main
package atomicElectronics;
import java.io.IOException;
import atomicElectronics.physical.AtomFrame;
import atomicElectronics.utility.Download;
public class Initial {
static AtomFrame atomLauncher;
public static void main(String[] args) {
atomLauncher = new AtomFrame();
atomLauncher.start();
System.out.println(Integer.MAX_VALUE);
Download theDownload = new Download();
theDownload.fileProgressBar(atomLauncher.progressBar);
try {
theDownload.exicute("http://download.videolan.org/pub/videolan/vlc/last/win64/vlc-2.1.3-win64.exe", "C:\\Users\\TrinaryAtom\\AppData\\Roaming");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// TODO Add Download Methods
// theDownload.updateBarTotal(JProgressBar);
// theDownload.updateLabelSpeed(String);
// theDownload.updateLabelTotal(String);
// theDownload.addFile(File);
// theDownload.addFiles(Files);
}
}
Class AtomFrame
package atomicElectronics.physical;
import javax.swing.JFrame;
import java.awt.FlowLayout;
import javax.swing.JProgressBar;
public class AtomFrame extends JFrame{
public JProgressBar progressBar;
private static final long serialVersionUID = 4010489530693307355L;
public static void main(String[] args){
AtomFrame testFrame = new AtomFrame();
testFrame.start();
}
public AtomFrame(){
initializeComponents();
}
public void initializeComponents(){
this.setSize(400, 400);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setTitle("Atom Launcher");
this.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
progressBar = new JProgressBar();
this.add(progressBar);
//this.pack();
}
public void start() {
this.setVisible(true);
}
public void close() {
this.dispose();
}
}
Class Download
package atomicElectronics.utility;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.swing.JProgressBar;
public class Download {
private static final int BUFFER_SIZE = 4096;
private JProgressBar fileProgressBar;
public Download() {
}
public void fileProgressBar(JProgressBar fileBar) {
fileProgressBar = fileBar;
}
public void exicute(String fileURL, String saveDir) throws IOException {
URL url = new URL(fileURL);
HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
int responseCode = httpConn.getResponseCode();
// always check HTTP response code first
if (responseCode == HttpURLConnection.HTTP_OK) {
String fileName = "";
String disposition = httpConn.getHeaderField("Content-Disposition");
String contentType = httpConn.getContentType();
double contentLength = httpConn.getContentLength();
if (disposition != null) {
// extracts file name from header field
int index = disposition.indexOf("filename=");
if (index > 0) {
fileName = disposition.substring(index + 9,
disposition.length());
}
} else {
// extracts file name from URL
fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1,
fileURL.length());
}
System.out.println("Content-Type = " + contentType);
System.out.println("Content-Disposition = " + disposition);
System.out.println("Content-Length = " + contentLength);
System.out.println("fileName = " + fileName);
// opens input stream from the HTTP connection
InputStream inputStream = httpConn.getInputStream();
String saveFilePath = saveDir + File.separator + fileName;
// opens an output stream to save into file
FileOutputStream outputStream = new FileOutputStream(saveFilePath);
double totalRead = 0;
int bytesRead = -1;
byte[] buffer = new byte[BUFFER_SIZE];
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
totalRead += bytesRead;
System.out.println((totalRead / contentLength) * 100);
fileProgressBar.setValue((int)((totalRead / contentLength) * 100));
}
outputStream.close();
inputStream.close();
System.out.println("File downloaded");
} else {
System.out.println("No file to download. Server replied HTTP code: " + responseCode);
}
httpConn.disconnect();
}
}

Suggestions:
Use a SwingWorker to do your background thread work.
Inside your SwingWorker, set its progress "bound" property via setProgress(int progress). The value should be between 1 and 100.
Don't have your SwingWorker/file downloader hold the JProgressBar or any Swing components.
Add a PropertyChangeListener to your SwingWorker and monitor changes in the progress property.
Never make your Swing fields (or most and and all fields) public. Limit access, and instead change object state via methods.
Read the tutorial Concurrency in Swing for the necessary details.
For example, the code below is a gross simplification and downloads no files, but should give you the idea:
import java.awt.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Random;
import javax.swing.*;
public class Initial {
static AtomFrame atomLauncher;
public static void main(String[] args) {
atomLauncher = new AtomFrame();
atomLauncher.start();
System.out.println(Integer.MAX_VALUE);
final Download theDownload = new Download();
theDownload.addPropertyChangeListener(new PropertyChangeListener() {
#Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if ("progress".equals(pcEvt.getPropertyName())) {
int progress = theDownload.getProgress();
atomLauncher.setProgress(progress);
}
}
});
theDownload.execute();
}
}
class AtomFrame extends JFrame {
// ********* should be private!
private JProgressBar progressBar;
private static final long serialVersionUID = 4010489530693307355L;
public static void main(String[] args) {
AtomFrame testFrame = new AtomFrame();
testFrame.start();
}
public void setProgress(int progress) {
progressBar.setValue(progress);
}
public AtomFrame() {
initializeComponents();
}
public void initializeComponents() {
this.setSize(400, 400);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setTitle("Atom Launcher");
this.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
progressBar = new JProgressBar();
this.add(progressBar);
// this.pack();
}
public void start() {
this.setVisible(true);
}
public void close() {
this.dispose();
}
}
class Download extends SwingWorker<Void, Void> {
private static final long SLEEP_TIME = 300;
private Random random = new Random();
#Override
protected Void doInBackground() throws Exception {
int myProgress = 0;
while (myProgress < 100) {
myProgress += random.nextInt(10);
setProgress(myProgress);
try {
Thread.sleep(SLEEP_TIME);
} catch (InterruptedException e) {}
}
return null;
}
}

issue with parsing log file continuously

I am trying to read a log file continuously where the logs are being written ,both the processes are happening simultaneously.I am using rolling file appender for generating logs but the problem is ,when the file is about to change sometimes the data written when the file is nearing end is not read.Here is my code that generates log file continuously.
import java.util.Timer;
import java.util.TimerTask;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public final class Slf4jSample {
static Logger logger = LoggerFactory.getLogger(Slf4jSample.class);
public static void main(final String[] args) {
int delay = 0; // delay for 5 sec.
int period = 1000; // repeat every sec.
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
int i = 0;
public void run() {
// Task here ...
for (i = 0; i < 50; i++) {
logger.error("testing" + i);
System.out.println(i);
}
}
}, delay, period);
}
}
and here is my code that is reading it continuously.
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Properties;
import java.util.Timer;
import java.util.TimerTask;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import com.mobility.config.ParseConfig;
import com.mobility.mail.SendMail;
import com.mobility.vo.ConfigurationVO;
import com.mobility.vo.LogVO;
import javax.mail.*;
TimerTask fileWatcherTask = new LogWatcher(fileName) {
long addFileLen = fileName.length();
FileChannel channel, oldChannel;
FileLock lock, oldLock;
#Override
protected void onChange(File file) {
RandomAccessFile access = null;
RandomAccessFile oldAccess = null;
int level = 0;
try {
access = new RandomAccessFile(file, "rw");
oldAccess = new RandomAccessFile(prevFileName, "rw");
channel = access.getChannel();
lock = channel.lock();
oldChannel = oldAccess.getChannel();
oldLock = oldChannel.lock();
// System.out.println("addFileLen>>" + addFileLen);
if (file.length() <= addFileLen) {
System.out.println("in if>>");
// reading old file
if (prevFileName.exists()) {
parsingLog(oldAccess, addFileLen,level);
addFileLen = file.length();
}
// reading old file ends
// Seek to 0th position when the file changes.
parsingLog(access, 0,level);
} else {
// access.seek(addFileLen);
parsingLog(access, addFileLen,level);
System.out.println("else>>>");
addFileLen = file.length();
}
} catch (Exception e) {
e.printStackTrace();
}
try {
lock.release();
oldLock.release();
} catch (IOException e1) {
e1.printStackTrace();
} // Close the file
try {
channel.close();
oldChannel.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Timer timer = new Timer();
// repeat the check every second
long scheduleTimer = Long.parseLong(properties
.getProperty("scheduler.timer"));
timer.schedule(fileWatcherTask, new Date(), scheduleTimer);
}
}
public void parsingLog(RandomAccessFile access, long fileLength, int level) {
List<String> logList = new ArrayList<String>();
int flag = 0;
String line = null;
try {
access.seek(fileLength);
while ((line = access.readLine()) != null) {
System.out.println("after reading line >"+line);
}
}catch(Exception e){
}
}
PS:it doesn't read the contents when it is nearing end.

I would open the file until it has been fully read and only close it when you have finished reading it. This may require your logger to create a new file each time, but you are unlikely to miss anything this way.

Make threads usage efficient in Java

I have coded a simple application in Java that downloads particular images from a list of html links provided. Everything was working fine until I added the feature of having to download from a list of html links rather than just one. I had to implement the wait() and notify() methods which forced me to change the approach a little. Now, the downloads work fine, but the GUI does not update while the download is in progress.
I make the 1st thread wait from HTML.java and notify it at the end of DownloadImages.java. For this I had to invoke buttonPressed class as an object rather than a thread, which is why I think my GUI won't update.
Is there a way to simplify or make thread-usage more efficient in my code? Thanks in advance.
Here is skeleton of my code:
/*Test.java*/
package my;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Test extends javax.swing.JFrame {
public static buttonPressed bp;
public static boolean alldone;
/** Creates new form Test */
public Test() {
initComponents();
}
public static class buttonPressed implements Runnable {
Thread t1, t2;
buttonPressed() {
t1 = new Thread(this, "downloadAction");
t1.start();
}
public void suspendThread() {
System.out.println("suspended");
alldone = false;
}
public synchronized void resumeThread() {
System.out.println("resumed");
alldone = true;
notify();
}
public void run() {
String[] len = new String[]{/*list of urls*/};
for (int i = 0; i &lt len.length; i++) {
System.out.println("going times: " + i);
t2 = new Thread(new HTML(), "HTMLthread");
t2.start();
synchronized (this) {
while (!alldone) {
try {
wait();
} catch (InterruptedException ex) {
Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
}
}
private void downloadActionPerformed(java.awt.event.ActionEvent evt) {
bp = new buttonPressed();
try {
bp.t1.join();
} catch (InterruptedException e) {
System.out.println("Main Thread: interrupted");
}
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Test().setVisible(true);
}
});
}
private javax.swing.JButton download;
public static javax.swing.JProgressBar progress;
}
/*HTML.java*/
package my;
import java.util.ArrayList;
class HTML implements Runnable {
private Thread t3;
public HTML() {
Test.bp.suspendThread();
}
public void run() {
downloadHTML();
ArrayList xyz = parseHTML();
t3 = new Thread(new DownloadImages(xyz), "DownDecrypt");
t3.start();
}
private void downloadHTML() {
// Downloads the HTML file
}
private ArrayList parseHTML() {
// Parses the HTML file and gets links to images
return new ArrayList();
}
}
/*DownloadImages.java*/
package my;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
class DownloadImages implements Runnable {
static int current = 0, previous = 0;
static boolean speedFlag;
ArrayList<String> links = new ArrayList<String>();
private Thread t4;
public DownloadImages(ArrayList param1) {
this.links = param1;
speedFlag = true;
}
public void run() {
t4 = new Thread(new getSpeed(), "getSpeed");
t4.start();
download(links);
}
private void download(ArrayList<String> param1) {
String[] imgurl = new String[param1.size()];
URLConnection conn = null;
InputStream is = null;
ByteArrayOutputStream bais = null;
int prog;
for (int i = 0; i < param1.size(); i++) {
current = 0;
imgurl[i] = param1.get(i);
try {
conn = new URL(imgurl[i]).openConnection();
int fsize = conn.getContentLength();
is = new BufferedInputStream(conn.getInputStream());
bais = new ByteArrayOutputStream();
byte[] byteChunk = new byte[1024];
int n;
while ((n = is.read(byteChunk)) > 0) {
bais.write(byteChunk, 0, n);
current = current + 1024;
prog = (int) (current * 100.0 / fsize);
Test.progress.setValue(prog);
}
} catch (MalformedURLException ex) {
Logger.getLogger(DownloadImages.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (is != null) {
try {
is.close();
} catch (IOException ex) {
Logger.getLogger(DownloadImages.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
byte[] imgBytes = bais.toByteArray();
try {
FileOutputStream fos = new FileOutputStream(i + ".jpg");
fos.write(imgBytes);
fos.flush();
fos.close();
} catch (FileNotFoundException ex) {
System.out.println("FileNotFoundException : " + ex);
} catch (IOException e) {
e.printStackTrace();
}
}
speedFlag = false;
// Resume the thread to start downloading the next link
Test.bp.resumeThread();
}
private static class getSpeed implements Runnable {
int kbytesPerSecond;
private final int fireTime;
public getSpeed() {
fireTime = 1000;
}
public void run() {
while (speedFlag) {
try {
Thread.sleep(fireTime);
} catch (InterruptedException ex) {
Logger.getLogger(getSpeed.class.getName()).log(Level.SEVERE, null, ex);
}
kbytesPerSecond = (((current - previous) / 1024) / (fireTime / 1000));
System.out.println(kbytesPerSecond);
previous = current;
}
}
}
}

As far as the GUI is concerned you need to read about Swing concurrency. In short, use SwingWorker.
Mind that you use old AWT stuff (java.awt.EventQueue).

I suggest you have an ExecutorService like Executors.newCachedThreadPool and submit() the tasks to it. Collect the Future objects so you know when they are done. This will be more efficient and manageable than creating Threads all over the place.
You can have just one pool like
static final ExecutorService POOL = Executors.newCachedThreadPool();
to submit a task
POOL.submit(new Callable<Void>() {
public Void call() throws InterruptedException {
while (speedFlag) {
Thread.sleep(1000);
kbytesPerSecond = (current - previous) / 1024;
System.out.println(kbytesPerSecond);
previous = current;
}
}
});
Even better for repeating tasks is to use a scheduled executor service.
static final ScheduledExecutorService POOL = Executors.newScheduledThreadPool(4);
Future task = POOL.scheduleAtFixedRate(new Runnable() {
public void run() {
kbytesPerSecond = (current - previous) / 1024;
System.out.println(kbytesPerSecond);
previous = current;
}
}, 1, 1, TimeUnit.SECONDS);
// to end the task
task.cancel(false);