How much memory do Enums take?

In Java, an enum is a full-blown class:

Java programming language enum types are much more powerful than their counterparts in other languages. The enum declaration defines a class (called an enum type). The enum class body can include methods and other fields.

In order to see the actual size of each enum, let's make an actual enum and examine the contents of the class file it creates.

Let's say we have the following Constants enum class:

public enum Constants {
  ONE,
  TWO,
  THREE;
}

Compiling the above enum and disassembling resulting class file with javap gives the following:

Compiled from "Constants.java"
public final class Constants extends java.lang.Enum{
    public static final Constants ONE;
    public static final Constants TWO;
    public static final Constants THREE;
    public static Constants[] values();
    public static Constants valueOf(java.lang.String);
    static {};
}

The disassembly shows that that each field of an enum is an instance of the Constants enum class. (Further analysis with javap will reveal that each field is initialized by creating a new object by calling the new Constants(String) constructor in the static initialization block.)

Therefore, we can tell that each enum field that we create will be at least as much as the overhead of creating an object in the JVM.

ZIP and UNZIP with Passwords in Java

Zip and Unzip are a very common activities for a computer user. A user normally uses the zip utility to compress a directory to create a zip file. There are many ready-made software such as winzip,7zip, and winrar that are available to achieve this. 

However, it is also possible to protect the zip file with a password so that the end user has to provide the password to unzip the zip file. This is the very common scenario that can be achieved by a zip utility tool. The significant part of my article is to provide you with the solution to achieve this using a Java program. While developing the project you may encounter a scenario in which you have to create a password-protected zip file that can be unzipped by any zip tool like winzip. Let me provide a complete scenario for your understanding.

In a system, some files are generated for a user and all the files are zipped with a password. The generated password protected zip file is sent to the user through email and the password for the zip file to open is sent to the particular user as an SMS to the user's mobile. 

 Similarly the end-user creates a password protected zip file and uploads to a online system with the user's password in a text field. In this case we have to develop a system where the system will be able to create a password protected zip file and should be able to extract all the files from a password protected zip file. Let me show you how you can achieve it.

Technicalities
However, Java provides the feature of creating a zip file and also provides the feature to unzip or decompress a zip file. But there is no default java API to create a password protected zip file and also there is no default java API to unzip a password protected zip file. To facilitate this feature of zip utility some developers have developed java API in this regard. We have to use their API to achieve this. We have to look into the following aspects of zip utility.

1. Java-enabled system should be able to generate a password protected zip file and that password protected zip file can be unzipped by any zip utility like winzip and others
2. Java-enabled system should be able to decompress or unzip a password protected zip file created by any zip utility like winzip and others.

The followings are the APIs you have to use for this objective:

1.To create a password protected zip file in java, you have to use “winzipaes”. It is avilable in Google code. You can download the .jar file and the source code from the following link.

"http://code.google.com/p/winzipaes/"

This API helps to add a password to a already created zip file. It means that if you want to create a password protected zip file, first you have to create a zip file and then you can add a password that zip file. It is a pure java API works with any operating system. You have to download the following jar file from the above URL.

passwordcompressor.jar

2.To unzip or decompress a password protected zip file, you have to use “sevenzipjbind”. It is available in sourceforge.net site. You can download the .jar files from the following link: http://sourceforge.net/projects/sevenzipjbind/files/. This API helps to extract all the files and folders from password protected zip file created by any zip utility tool. You have to download the following .jar files from the above URL.

sevenzipjbinding-AllPlatforms.jar
sevenzipjbinding.jar

3.For password protection, you have to use Bouncecastle cryptographic API. You can download the .jar file from the following link.
http://www.bouncycastle.org/
You have to download the following .jar files from the above URL.
bcprov-jdk15-145.jar

After downloading all the .jar files, put all the .jar files in your classpath. I have written a java program by using all these APIs to achieve all the above mentioned functionalities.

Have a look at the following code structure.

Code for ZipUtil.java

	import java.io.File;
	import java.io.FileInputStream;
	import java.io.FileNotFoundException;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.io.OutputStream;
	import java.io.RandomAccessFile;
	import java.util.Arrays;
	import java.util.zip.ZipEntry;
	import java.util.zip.ZipInputStream;
	import java.util.zip.ZipOutputStream;
	import de.idyl.crypto.zip.AesZipFileEncrypter;
	import net.sf.sevenzipjbinding.ExtractOperationResult;
	import net.sf.sevenzipjbinding.ISequentialOutStream;
	import net.sf.sevenzipjbinding.ISevenZipInArchive;
	import net.sf.sevenzipjbinding.SevenZip;
	import net.sf.sevenzipjbinding.SevenZipException;
	import net.sf.sevenzipjbinding.impl.RandomAccessFileInStream;
	import net.sf.sevenzipjbinding.simple.ISimpleInArchive;
	import net.sf.sevenzipjbinding.simple.ISimpleInArchiveItem;
	/**
	* This is a utility class having utility method for various kinds of zip and
	* unzip operation. This class performs the following operations. 1. Normal
	* zipping a directory 2. Zipping a directory with password 3. Normal unzipping
	* a zip file 4. Unzipping a password protected zip file
	*
	* @author Jay Thakkar
	*
	*/
	public class ZipUtil {
	/**
	* This method is used to write the contents from a zip file to a file
	*
	* @param file
	* of type {@link File}
	* @param zipIn
	* of type {@link ZipInputStream}
	*/
	private static void writeFile(File file, ZipInputStream zipIn) {
	try {
	OutputStream outStream = new FileOutputStream(file);
	byte[] buff = new byte[1024];
	int len;
	while ((len = zipIn.read(buff)) > 0) {
	outStream.write(buff, 0, len);
	}
	outStream.close();
	} catch (Exception e) {
	e.printStackTrace();
	}
	}
	/**
	* This method is used to extract the zip file to a destination directory
	*
	* @param srcZipfile
	* of type {@link File} indicating the source zip file
	* @param destinationDir
	* of type {@link File} indicating the destination directory
	* where the zip file will be extracted.
	* @throws IOException
	*/
	private static void extract(File srcZipfile, File destinationDir)
	throws IOException {
	ZipInputStream zipIn = null;
	try {
	zipIn = new ZipInputStream(new FileInputStream(srcZipfile));
	ZipEntry entry = null;
	while ((entry = zipIn.getNextEntry()) != null) {
	String outFilename = entry.getName();
	if (!new File(destinationDir, outFilename).getParentFile()
	.exists())
	new File(destinationDir, outFilename).getParentFile()
	.mkdirs();
	if (!entry.isDirectory())
	writeFile(new File(destinationDir, outFilename), zipIn);
	}
	System.out.println("Zip file extracted successfully...");
	} catch (Exception e) {
	e.printStackTrace();
	} finally {
	if (zipIn != null) {
	zipIn.close();
	}
	}
	}
	/**
	* This method is used to zip or compress a directory to create a zip file.
	*
	* @param directory
	* of type String indicating the source directory to be zipped
	* @param zos
	* of type {@link ZipOutputStream}
	* @param path
	* of type String indicating the path
	* @throws IOException
	*/
	private static void compressDir(String directory, ZipOutputStream zos,
	String path) throws IOException {
	File zipDir = new File(directory);
	String[] dirList = zipDir.list();
	byte[] readBuffer = new byte[2156];
	int bytesIn = 0;
	for (int i = 0; i < dirList.length; i++) {
	File f = new File(zipDir, dirList[i]);
	if (f.isDirectory()) {
	String filePath = f.getPath();
	compressDir(filePath, zos, path + f.getName() + "/");
	continue;
	}
	FileInputStream fis = new FileInputStream(f);
	try {
	ZipEntry anEntry = new ZipEntry(path + f.getName());
	zos.putNextEntry(anEntry);
	bytesIn = fis.read(readBuffer);
	while (bytesIn != -1) {
	zos.write(readBuffer, 0, bytesIn);
	bytesIn = fis.read(readBuffer);
	}
	} catch (Exception e) {
	e.printStackTrace();
	} finally {
	fis.close();
	}
	}
	}
	/**
	* This method is used to zip a directory
	*
	* @param dirName
	* of type String indicating the path of the directory to be
	* zipped
	* @param zipFileName
	* of type String indicating the file name for the zip file
	*/
	public static void zipDir(String dirName, String zipFileName) {
	if (zipFileName == null) {
	File tempFile = new File(dirName);
	zipFileName = tempFile.getAbsoluteFile().getParent()
	+ File.separator + tempFile.getName() + ".zip";
	}
	try {
	ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(
	zipFileName));
	compressDir(dirName, zos, new File(dirName).getName()
	+ File.separator);
	zos.close();
	} catch (NullPointerException npe) {
	npe.printStackTrace();
	} catch (FileNotFoundException e) {
	e.printStackTrace();
	} catch (IOException ie) {
	ie.printStackTrace();
	}
	}
	/**
	* This method is used to create a password protected zip file.
	*
	* @param dirName
	* of type String indicating the name of the directory to be
	* zipped
	* @param zipFileName
	* of type String indicating the name of the zip file to be
	* created
	* @param password
	* of type String indicating the password
	*/
	public static void zipDirWithPassword(String dirName, String zipFileName,
	String password) {
	if (zipFileName == null) {
	File tempFile = new File(dirName);
	zipFileName = tempFile.getAbsoluteFile().getParent()
	+ File.separator + tempFile.getName() + ".rar";
	}
	zipDir(dirName, zipFileName);
	String tempZipFileName = new File(dirName).getAbsoluteFile()
	.getParent() + File.separator + "tempencrypted.rar";
	try {
	AesZipFileEncrypter enc = new AesZipFileEncrypter(tempZipFileName);
	enc.addEncrypted(new File(zipFileName), password);
	new File(zipFileName).delete();
	new File(tempZipFileName).renameTo(new File(zipFileName));
	} catch (IOException e) {
	e.printStackTrace();
	}
	}
	/**
	* This method is used to unzip a zip file to a directory
	*
	* @param sourceZipFile
	* of type String indicating the source zip file
	* @param destinationDir
	* of type String indicating the destination directory where the
	* zip file will be extracted.
	*/
	public static void unzipDir(String sourceZipFile, String destinationDir) {
	try {
	extract(new File(sourceZipFile), new File(destinationDir));
	} catch (Exception e) {
	e.printStackTrace();
	}
	}
	/**
	* This method is used to unzip a password protected zip file.
	*
	* @param sourceZipFile
	* of type String indicating the source zip file
	* @param destinationDir
	* of type String indicating the directory where the zip file
	* will be extracted.
	* @param password
	* of type String indicating the password.
	*/
	public static void unzipDirWithPassword(final String sourceZipFile,
	final String destinationDir, final String password) {
	RandomAccessFile randomAccessFile = null;
	ISevenZipInArchive inArchive = null;
	try {
	randomAccessFile = new RandomAccessFile(sourceZipFile, "r");
	inArchive = SevenZip.openInArchive(null, // autodetect archive type
	new RandomAccessFileInStream(randomAccessFile));
	// Getting simple interface of the archive inArchive
	ISimpleInArchive simpleInArchive = inArchive.getSimpleInterface();
	for (final ISimpleInArchiveItem item : simpleInArchive
	.getArchiveItems()) {
	final int[] hash = new int[] { 0 };
	if (!item.isFolder()) {
	ExtractOperationResult result;
	result = item.extractSlow(new ISequentialOutStream() {
	public int write(final byte[] data)
	throws SevenZipException {
	try {
	if (item.getPath().indexOf(File.separator) > 0) {
	String path = destinationDir
	+ File.separator
	+ item.getPath().substring(
	0,
	item.getPath().lastIndexOf(
	File.separator));
	File folderExisting = new File(path);
	if (!folderExisting.exists())
	new File(path).mkdirs();
	}
	OutputStream out = new FileOutputStream(
	destinationDir + File.separator
	+ item.getPath());
	out.write(data);
	out.close();
	} catch (Exception e) {
	e.printStackTrace();
	}
	hash[0] |= Arrays.hashCode(data);
	return data.length; // Return amount of proceed data
	}
	}, password); // / password.
	if (result == ExtractOperationResult.OK) {
	System.out.println(String.format("%9X | %s", hash[0],
	item.getPath()));
	} else {
	System.err.println("Error extracting item: " + result);
	}
	}
	}
	} catch (Exception e) {
	e.printStackTrace();
	} finally {
	if (inArchive != null) {
	try {
	inArchive.close();
	} catch (SevenZipException e) {
	System.err.println("Error closing archive: " + e);
	e.printStackTrace();
	}
	}
	if (randomAccessFile != null) {
	try {
	randomAccessFile.close();
	} catch (IOException e) {
	System.err.println("Error closing file: " + e);
	e.printStackTrace();
	}
	}
	}
	}
	}

view raw ZipUtil.java hosted with ❤ by GitHub

DicomMultiframePlayer in JAVA

package packageTestDcm4che3;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.Vector;
import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;

import javax.imageio.ImageReader;
import javax.imageio.spi.ImageReaderSpi;
import javax.imageio.stream.FileImageInputStream;
import javax.imageio.stream.ImageInputStream;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import org.dcm4che.imageio.plugins.dcm.DicomImageReadParam;
import org.dcm4che.imageio.plugins.dcm.DicomImageReader;

/**
 * Plays a multiframe DICOM instance.
 *
 * @author dimitri PIANETA
 *
 * <p>The code for this came from <a href="http://samucs.blogspot.com" target="_blank">http://samucs.blogspot.com</a>
 *    and was dated 6-January-2010.</p>
 *
 * <p> code modification 14 January 2014 for dcm4che3 <p>
 */   
public class DicomMultiframePlayer extends JFrame implements ActionListener, Runnable {
   
    private static final long serialVersionUID = 1L;
    private JLabel fileLabel;
    /**
     * Will contain name of file to be read.
     */
    private JTextField fileField;
    /**
     * Triggers process for selecting file to be read.
     * @see #actionPerformed(ActionEvent)
     */
    private JButton btnChoose;
    /**
     * Starts playing of images.
     * @see #actionPerformed(ActionEvent)
     */
    private JButton btnPlay;
    /**
     * Pauses playing of images.
     * @see #actionPerformed(ActionEvent)
     */
    private JButton btnPause;
    /**
     * Halts playing of images.
     * @see #actionPerformed(ActionEvent)
     */
    private JButton btnStop;
    private JButton btnExit;   
    private Vector<BufferedImage> images;
    private ImagePanel imagePanel;   
    private boolean stop;
    private int currentFrame;
   
       
        private int frame = 1;

       
       
       
          private final ImageReader imageReader =
            ImageIO.getImageReadersByFormatName("DICOM").next();
       
       
    public DicomMultiframePlayer() {
        super("DICOM Multiframe Player using dcm4che - by samucs-dev");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.getContentPane().setLayout(new BorderLayout());
       
        images = new Vector<BufferedImage>();
        imagePanel = new ImagePanel();
       
        fileLabel = new JLabel("File:");
        fileField = new JTextField(30);
        btnChoose = this.createJButton(25, 25, "...");
       
        btnPlay = this.createJButton(80,25,"Play");
        btnPause = this.createJButton(80,25,"Pause");
        btnStop = this.createJButton(80,25,"Stop");       
        btnExit = this.createJButton(80,25,"Exit");
        btnPause.setEnabled(false);
        btnStop.setEnabled(false);
       
        JPanel panelNorth = new JPanel();
        panelNorth.add(fileLabel);
        panelNorth.add(fileField);
        panelNorth.add(btnChoose);
       
        JPanel panelSouth = new JPanel();
        panelSouth.add(btnPlay);
        panelSouth.add(btnPause);
        panelSouth.add(btnStop);
        panelSouth.add(btnExit);
       
        this.getContentPane().add(panelNorth, BorderLayout.NORTH);
        this.getContentPane().add(imagePanel, BorderLayout.CENTER);
        this.getContentPane().add(panelSouth, BorderLayout.SOUTH);
       
        this.setSize(new Dimension(500,500));
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }
    /**
     * Plays the frames in order.
     *
     * <p>I removed the Override annotation.</p>
     */
    // @Override
    public void run() {
        while(true) {
            if (!btnPlay.isEnabled()) {               
                if (stop) break;               
                currentFrame++;
                if (currentFrame == images.size())
                    currentFrame = 0;
                imagePanel.setImage(images.get(currentFrame));               
                try {
                    Thread.sleep(70);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    /**
     * Detects clicking of button and carries out appropriate action.
     *
     * <p>I removed the Override annotation.</p>
     */
    // @Override
    public void actionPerformed(ActionEvent e) {       
        if (e.getSource().equals(btnChoose)) {
            JFileChooser chooser = new JFileChooser();
            int action = chooser.showOpenDialog(this);
            switch(action) {
                case JFileChooser.APPROVE_OPTION:
                    this.openFile(chooser.getSelectedFile());
                    break;
                case JFileChooser.CANCEL_OPTION:
                    return;
            }
        }       
        if (e.getSource().equals(btnPlay)) {
            btnPlay.setEnabled(false);
            btnPause.setEnabled(true);
            btnStop.setEnabled(true);
            stop = false;
            new Thread(this).start();           
        }
        if (e.getSource().equals(btnPause)) {
            btnPlay.setEnabled(true);
            btnPause.setEnabled(false);
            btnStop.setEnabled(true);
            stop = false;
        }
        if (e.getSource().equals(btnStop)) {
            btnPlay.setEnabled(true);
            btnPause.setEnabled(false);
            btnStop.setEnabled(false);
            stop = true;
            currentFrame = 0;
            imagePanel.setImage(images.get(0));           
        }
        if (e.getSource().equals(btnExit)) {
            System.exit(0);
        }
    }
    /**
     * Creates JButton objects on window.
     * @param width width of button in pixels.
     * @param height height of button in pixels
     * @param text text to appear in button
     * @return JButton object
     */
    private JButton createJButton(int width, int height, String text) {
        JButton b = new JButton(text);
        b.setMinimumSize(new Dimension(width, height));
        b.setMaximumSize(new Dimension(width, height));
        b.setPreferredSize(new Dimension(width, height));
        b.addActionListener(this);
        return b;
    }
    /**
     * Reads the contents of the dicom file
     * @param file file to be opened
     * @see org.dcm4che2.imageioimpl.plugins.dcm.DicomImageReaderSpi
     * @see org.dcm4che2.imageioimpl.plugins.dcm.DicomImageReader
     */
    private void openFile(File file) {
        images.clear();
        try {
           
                   
                       
            int numFrames =setNumber(file);
            //System.out.println("DICOM image has "+ numFrames +" frames...");           
            System.out.println("Extracting frames...");
            for (int i=0; i < numFrames; i++) {
                     
                       
                          
                BufferedImage img =  chargeImageDicomBufferise(file,i);
                images.add(img);
                System.out.println(" > Frame "+ (i+1));
            }           
            System.out.println("Finished.");
        } catch(Exception e) {
            e.printStackTrace();
            imagePanel.setImage(null);
            return;
        }
        stop = false;
        currentFrame = 0;
        imagePanel.setImage(images.get(0));
    }

     
       
        /**
         * Building BufferingImage
         * @param file : input file
         * @param value : number frame
         * @return
         * @throws IOException
         */
       
        public BufferedImage chargeImageDicomBufferise(File file, int value) throws IOException  {

                Iterator<ImageReader> iter = ImageIO.getImageReadersByFormatName("DICOM");//sp?cifie l'image

                              
                         

              ImageReader readers = iter.next();//on se d?place dans l'image dicom

         DicomImageReadParam   param1 =  (DicomImageReadParam) readers.getDefaultReadParam();//return DicomImageReadParam
               //    Adjust the values of Rows and Columns in it and add a Pixel Data attribute with the byte array from the DataBuffer of the scaled Raster

                ImageInputStream iis = ImageIO.createImageInputStream(file);

             readers.setInput(iis, false);//sets the input source to use the given ImageInputSteam or other  Object

               BufferedImage image = readers.read(value,param1);//BufferedImage image = reader.read(frameNumber, param); frameNumber = int qui est l'imageIndex
                System.out.println(image);//affichage au terminal des caract?res de l'image

                readers.dispose();//Releases all of the native sreen resources used by this Window, its subcomponents, and all of its owned children
              return  image;

            }
   
         /**
 *  Find number frame
 * @param file : input file
 * @return numbre frame in Dicom
 * @throws IOException
 */
   public int setNumber(File file) throws IOException  {

            /* Parcourt le fichier dicom*/
             Iterator<ImageReader> iter = ImageIO.getImageReadersByFormatName("DICOM");//sp?cifie l'image
           ImageReader readers = (ImageReader)iter.next();//on se d?place dans l'image dicom

            DicomImageReadParam   param1=  (DicomImageReadParam) readers.getDefaultReadParam();//return DicomImageReadParam
           //    Adjust the values of Rows and Columns in it and add a Pixel Data attribute with the byte array from the DataBuffer of the scaled Raster

            ImageInputStream iis = ImageIO.createImageInputStream(file);//cr?ation du fichier image


           readers.setInput(iis, false);//sets the input source to use the given ImageInputSteam or other  Object

            //iis.close();
            int  number = readers.getNumImages(true);//numberOfFrame on a "readers" qui doit ?tre DicomImage
            System.out.println(number);//return NumberOfFrame (Tag : (0028, 0008))
           return  number;
        }
   
   
   
    private class ImagePanel extends JPanel {
        private static final long serialVersionUID = 1L;
        private BufferedImage image;
        private int frame;
        public ImagePanel() {
            super();
            this.setPreferredSize(new Dimension(1024,1024));
            this.setBackground(Color.black);           
        }
        public void setImage(BufferedImage image) {
            this.image = image;
            this.updateUI();
        }
        @Override
        public void paint(Graphics g) {
            if (this.image != null) {
                g.drawImage(this.image, 0, 0, image.getWidth(), image.getHeight(), null);
            }
        }
   
        };

    public static void main(String[] args) {
        new DicomMultiframePlayer();
    }

}

JAVAFX: Dynamically fire event to Node

Event.fireEvent(vbox, new MouseEvent(MouseEvent.MOUSE_CLICKED, 0,
                    0, 0, 0, MouseButton.PRIMARY, 1, true, true, true, true,
                    true, true, true, true, true, true, null));

How do I implement task prioritization using an ExecutorService in Java 5?

package example;

import java.util.Comparator;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.PriorityBlockingQueue;
import java.util.concurrent.RunnableFuture;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

class PriorityFuture<T> implements RunnableFuture<T> {

    private RunnableFuture<T> src;
    private int priority;

    public PriorityFuture(RunnableFuture<T> other, int priority) {
        this.src = other;
        this.priority = priority;
    }

    public int getPriority() {
        return priority;
    }

    public boolean cancel(boolean mayInterruptIfRunning) {
        return src.cancel(mayInterruptIfRunning);
    }

    public boolean isCancelled() {
        return src.isCancelled();
    }

    public boolean isDone() {
        return src.isDone();
    }

    public T get() throws InterruptedException, ExecutionException {
        return src.get();
    }

    public T get(long timeout, TimeUnit unit) throws InterruptedException,
            ExecutionException, TimeoutException {
        return src.get();
    }

    public void run() {
        src.run();
    }

    public static Comparator<Runnable> COMP = new Comparator<Runnable>() {
        public int compare(Runnable o1, Runnable o2) {
            if (o1 == null && o2 == null)
                return 0;
            else if (o1 == null)
                return -1;
            else if (o2 == null)
                return 1;
            else {
                int p1 = ((PriorityFuture<?>) o1).getPriority();
                int p2 = ((PriorityFuture<?>) o2).getPriority();

                return p1 > p2 ? 1 : (p1 == p2 ? 0 : -1);
            }
        }
    };
}

interface PriorityCallable<T> extends Callable<T> {
    int getPriority();
}

class LenthyJob implements PriorityCallable<Long> {
    private int priority;

    public LenthyJob(int priority) {
        this.priority = priority;
    }

    public Long call() throws Exception {
        System.out.println("Executing: " + priority);
        long num = 1000000;
        for (int i = 0; i < 1000000; i++) {
            num *= Math.random() * 1000;
            num /= Math.random() * 1000;
            if (num == 0)
                num = 1000000;
        }
        return num;
    }

    public int getPriority() {
        return priority;
    }
}

public class TestPQ {

    public static ThreadPoolExecutor getPriorityExecutor(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads, 0L,
                TimeUnit.MILLISECONDS, new PriorityBlockingQueue<Runnable>(10,
                        PriorityFuture.COMP)) {

            protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
                System.out.println("######## newTaskFor : -------");
                RunnableFuture<T> newTaskFor = super.newTaskFor(callable);
               
                return new PriorityFuture<T>(newTaskFor,
                        ((PriorityCallable<T>) callable).getPriority());
            }
        };
    }

    public static void main(String[] args) throws InterruptedException,
            ExecutionException {
        ThreadPoolExecutor exec = getPriorityExecutor(2);

        for (int i = 0; i < 20; i++) {
            int priority = (int) (Math.random() * 100);
            System.out.println("Scheduling: " + priority);
            LenthyJob job = new LenthyJob(priority);
            exec.submit(job);
        }
    }
}

Thread output in certain order

package threadseq;

import java.util.*;

public class OrderThreads {
public static void main(String... args) {
Results results = new Results();
new Thread(new Task(0, "red", results)).start();
new Thread(new Task(1, "orange", results)).start();
new Thread(new Task(2, "yellow", results)).start();
new Thread(new Task(3, "green", results)).start();
new Thread(new Task(4, "blue", results)).start();
new Thread(new Task(5, "indigo", results)).start();
new Thread(new Task(6, "violet", results)).start();
}
}

class Results {
private List<String> results = new ArrayList<String>();
private int i = 0;

public synchronized void submit(int order, String result) {
while (results.size() <= order){
results.add(null);
}
results.set(order, result);
while ((i < results.size()) && (results.get(i) != null)) {
System.out.println("result delivered: " + i + " " + results.get(i));
++i;
}
}
}

class Task implements Runnable {
private final int order;
private final String result;
private final Results results;

public Task(int order, String result, Results results) {
this.order = order;
this.result = result;
this.results = results;
}

public void run() {
try {
Thread.sleep(Math.abs(result.hashCode() % 1000)); // simulate a
// long-running
// computation
} catch (InterruptedException e) {
} // you'd want to think about what to do if interrupted
System.out.println("task finished: " + order + " " + result);
results.submit(order, result);
}
}

Convert BufferedImage To ByteBuffer

In applet its very simple to do this

BufferedImage originalImage = ImageIO.read(new File("c:\\image\\mypic.jpg"));

ByteArrayOutputStream baos = new ByteArrayOutputStream();

ImageIO.write( originalImage, "jpg", baos );

baos.flush();

byte[] imageInByte = baos.toByteArray();

baos.close()

ByteBuffer buf = ByteBuffer.wrap(imageInByte);