Thread start() method problem

I have a program server-client program that have a lot thread but
when I called thread.start() method it doesn't return run() method.
even so my input-output codes is running ( my client program can send data to server program )
Please help me

yasinmalli wrote:
start() method doesn't call run() method of thread when I debug row to rowIt does, but the debugger will only ever follow the flow of the current thread and therefore not step into the run method. Set a breakpoint at the very beginning of your run() method and then step over the start() method, you'll see that the new thread will break exactly at that breakpoint just after start() was executed.

Similar Messages

How to view source of native method Thread.start()

I have already downloaded and unzipped the source code for JDK. I want to view the implementation of Thread.start() method. However, I can only see one line:
public synchronized native void start();Could anyone tell me how can view the implementation of this method? And generally, how can I view the implementation of a native method?
Regards,
Xinjun

%SRC_BASE%\j2se\src\share\native\java\lang\Thread.c,
but that only defines a table in which start0()
forwards you to JVM_StartThread(), wherever that may
be.You are crossing the boundary between the JDK code and the JVM (Java Virtual Machine). If you have unpacked the Mustang sources [1], take a look at:
hotspot/src/share/vm/prims/jvm.cpp lines 2421 through 2504.
This will soon lead you to hotspot/src/share/vm/runtime/thread.cpp
Hope this helps...
[1] https://mustang.dev.java.net/

Thread.run() method..

I was wondering how the "Thread.run()" method get called. I started with "Thread.start()" and found it calls the "Thread.start0()" which is a native method.
I downloaded the JDK 5 source code and went to "j2se\src\share\native\java\lang\Thread.c". In "Thread.c" I found a mapping of "start0()" with "JVM_StartThread".
After that I opened the "hotspot\src\share\vm\prims\jvm.cpp". From line no 2257 to 2316 I saw the implementation of "JVM_StartThread".
In side "JVM_StartThread", I saw there is a call to "Thread::start(native_thread)" and opened the "hotspot\src\share\vm\runtime\Thread.cpp". In "Thread.start()" method there is a call to "os::start_thread(thread);".
In "hotspot\src\share\vm\runtime\os.cpp" the "os::start_thread()" calls the "pd_start_thread(thread);" method. But I did not get the "pd_start_thread(thread);" method in os.cpp.
Note: I am java programmer and hardly understand the C/C++ languages. But had a doubt how the run() method get called and how the Thread.start() method works. But I got stuck here.
Kindly help me to know how the flow goes, when we call the Thread.start() and how the run() method is linked to it.

But I did not see anything in the os.cpp. In fact i did not find the "pd_start_thread(thread);" .
void os::start_thread(Thread* thread) {
// guard suspend/resume
MutexLockerEx ml(thread->SR_lock(), Mutex::_no_safepoint_check_flag);
assert(thread->is_baby_thread(), "thread has started");
thread->clear_is_baby_thread();
OSThread* osthread = thread->osthread();
// A thread may be suspended in the presence of the profiler.
// Only start thread when it's not suspended.
osthread->set_state(RUNNABLE);
if (!thread->is_vm_suspended()) {
pd_start_thread(thread);
}

How start() method map run()

Can any one give me some idea-
How thread start() method calls run() method of Runnable interface???
Please help me?

There's no trick to it, I assume the start() method contains a call to someRunnable.run();
Example:
public void start() {
doStuff();
runnable.run();
}Of course it can't be that simple since start must return immediately and run() will continue running in it's own thread...
In other words, you don't need to worry about that.

Can a thread's start() method be called more than once?

Is it legal/well-defined to call a Thread object's start() method after a previous call to start() has completed?
eg.
Thread t = new Thread(public void run() {...});
t.start();
t.join();
t.start(); // will this call fail?

Ok, since no one's going to answer you I will.
Yes. It won't work if you call start() multiple times and it will throw an exception on all subsequent times.
The way I work around it is to put the method in an inner-class and then create a new instance of that iner-class everytime I want to start a new thread.

Why java allow start() method only once for a thread

Hi ,
Why java allows start method only once for thread . suppose
Thread t = new Thread();
t.start();
say at later stage if again we call t.start() IllegalStateException is thrown , even though isAlive method returns false.
Hence the question , why start() method is allowed only once.If you need start a thread , we need to create a new instance.

Really. Why do you think that? Do you have any evidence? It is one of the first things I would think of, personally.Considering that the Thread API doesn't allow you to specify a stack address (only stack size), I think it demonstrates they wanted to remove that capability from their Thread API all together. That missing "capability" makes me believe they want me to believe it's not something I need to worry about when using their API... I think the exact semantics of the Thread class and its methods were driven by how to make it most understandable and usable for their customers. I'm certain this issue was one of many that was given considerable thought during the design and implementation of the JVM and the underlying runtime classes.
Do I have any evidence? No. But if you can point me at some first-hand information on this, I'd love to read it. Most of what I've found is second or third hand accounts. (and I mean that sincerely, not as a smart-ass remark or rebuke of your comments).
On the one hand you seem to think the Java API designers are idiots, on the other hand you think that they should be. I can't make it out.I thought my position was that the Java developers were talented enough to implement platform in whatever way their API called for; hence, the designers made a choice about how they wanted their API to be used by their customers. They decided which capabilities they wanted to include or exclude, and created an API that was consistent with their vision for this technology. While I'm certain technical limitations had an effect on the API design, I certainly don't think the API was dictated by the them.
I think the current design of the Java Thread API was a reflection of their vision to make Threading easier and more accessible to Joe Programmer, not limitations in the implementation. I never said it was wrong or that I could do better... I just said I think they could have done something different if they decided it would have made for a better customer experience. But hey, maybe I'm wrong.

Query on Thread.setDaemon method......

I have a small conceptual problem.
I wrote a small program which starts a thread
from it's main method and marks it as Daemon.
The Thread actually starts an infinite loop.
Inside the run method of another Thread I start another Thread
which is also an infinite loop. I mark it as non-daemon(although I don't need to as default is daemon).
But when I ran the program I found that the program terminates
after some time. As What I know about threads it should not have stopped
becz. a non daemon thread was running. Plz. explain it.
Both the Classes are paster below.
Nimesh
/*Class::Test 1*/
public class Test1 implements Runnable{
private static Test2 test2=null;
private static Thread thread2=null;
public static void main(String args[]){
Test1 test2=new Test1();
Thread thread1=new Thread(test2);
thread1.setDaemon(true);
thread1.start();
public void run(){
test2=new Test2();
thread2=new Thread(test2);
thread2.setPriority(Thread.NORM_PRIORITY );
thread2.setDaemon(false);
thread2.start();
System.out.println("Got here");
while(true){
func1();
public void func1() {
System.out.println("In Thread 1");
/*Class: Test1*/
public class Test2 implements Runnable{
public void run(){
while(true){
func1();
public void func1(){
System.out.println("In Thread2");

I think that you have two problems
1) there is a chance that the second thread would not have started, because i think the start method does not actually garuantee that the second thread is actually started when the method returns. If you want to garuantee that the second thread has started you need to wait on some synchronized block of code in thread one after you have called the start method for thread two. Then thread two needs to call a notify method in its run method.
2) Your main method is exiting before all the threads are starting, i would put a sleep of say 1ms to let the other threads start or a syncrhonized block.

Thread.start() without run() invoke

We got interesting problem during migration one old application from java 1.4.2_08 to the java 1.5.0_06. The principal code of application is:
public class objServ extends Thread {
public void run() {
     while (!End) {
           clientSocket = ServSocket.accept();
           client = new objClient(this, clientSocket);
           logger.sendInfo("client created. "+client.getName());
           client.start();
           logger.sendInfo("client start done. "+client.getName());
public static void main(String args[]) {
      pkvserv serv = new objServ(hostName, port);
      serv.start();
public class objClient extends Thread {
   // client method run()
public void run() {
     printlog("Thread run started. "+this..getName());
}The application listen port and generate the client thread for each connection.
After 10 days of using this application and generating and successful processing and termination of near 340000 client threads we got a situation when client thread was created, method start() was invoked, but the client method run() was never invoke.
Does anybody have any idea why this situation can happen? We have memory monitoring on that application and it�s was not a memory problem.

So you're claiming there's a bug in the VM. I doubt it (at least not one of the nature you're claiming). I'd suspect your code didn't execute start(), or that if it did, run() did execute and you're making a faulty conclusion that it didn't.

Creating breakout game. Need help with thread starting.

Howdy. As the title says, I've got an assignment to make a breakout game. So far it's going alright, but I've run into a rather large snag...I can't get it to animate :P I've got my main applet, then I created a class heirarchy for the paddle, ball, and brick objects. For this question, lets just focus on the ball object.
This is my applet code so far (it is not even close to being done, so don't laugh :P )
import java.awt.*;
import javax.swing.*;
import java.util.*;
* Class BreakoutApplet - Plays a simple game of Breakout.
* @author Kris Nelson
* @version November 10, 2004
public class BreakoutApplet extends JApplet implements Runnable
    protected Brick brick; // creates an object of class brick
    protected Ball ball; // creates an object of class ball
    protected Paddle paddle; // creates an object of class paddle
    protected boolean running; // tells the program whether or not the thread is running
    protected ArrayList brickArray = new ArrayList(); // stores all the bricks in the game
    protected Thread timer; // the thread which controls the animation for the applet
    * Called by the browser or applet viewer to inform this JApplet that it
    * has been loaded into the system. It is always called before the first
    * time that the start method is called.
    public void init()
        // this is a workaround for a security conflict with some browsers
        // including some versions of Netscape & Internet Explorer which do
        // not allow access to the AWT system event queue which JApplets do
        // on startup to check access. May not be necessary with your browser.
        JRootPane rootPane = this.getRootPane();
        rootPane.putClientProperty("defeatSystemEventQueueCheck", Boolean.TRUE);
        createBricks(); // creates the games array of bricks
        ball = new Ball(400, 400, 2, 2); // sets the values for the ball
        paddle = new Paddle(300, 660, 2); // sets the values for the paddle
        // !!!!!!! have tried placing ball.start() here
    * Paint method for applet.
    * @param g   the Graphics object for this applet
    public void paint(Graphics g)
        // draws the background, border, and all the games objects
        g.setColor(Color.lightGray); // sets the drawing color to light gray
        g.fillRect(0, 0, 600, 700); // displays the game screens background
        displayBorder(g); // displays the game screens border
        displayBricks(g); // displays the array of bricks
        ball.display(g); // displays the ball
        paddle.display(g); // displays the paddle
    * Creates the games array of bricks
    public void createBricks()
        int colorNumber = 1; // starts the color of the bricks at orange
        double yPosition = 100; // starts the bricks y screen position at 100
        for(int i = 0; i < 4; i++)
            double xPosition = 12; // starts the bricks x screen position at 12
            for(int j = 0; j < 8; j++)
                if(colorNumber == 0)
                    colorNumber = 1; // sets the color of the bricks to orange
                else
                    colorNumber = 0; // sets the color of the bricks to green
                brickArray.add(brick = new Brick(xPosition, yPosition, colorNumber)); // adds a brick to the current container in the brick array
                xPosition = xPosition + brick.getWidth(); // move the bricks x screen position to the next column
            yPosition = yPosition + brick.getHeight(); // moves the bricks y screen position to the next row
            if(colorNumber == 0)
                colorNumber = 1; // sets the color of the bricks to orange
            else
                colorNumber = 0; // sets the color of the bricks to green
    * Displays the game screens border
    * @param g   the Graphics object for this applet
    public void displayBorder(Graphics g)
        g.setColor(Color.black); // sets the drawing color to black
        g.fillRect(0, 0, 600, 24); // draws a border on the top of the screen
        g.fillRect(0, 0, 12, 700); // draws a border on the left of the screen
        g.fillRect(588, 0, 12, 700); // draws a border on the right of the screen
    * Displays the array of bricks on the screen
    * @param g   the Graphics object for this applet
    public void displayBricks(Graphics g)
        Brick currentBrick; // holds the brick data from the current ArrayList container
        for(int i = 0; i < 32; i++)
            currentBrick = (Brick)(brickArray.get(i)); // grabs the brick data from the current ArrayList container
            currentBrick.display(g); // displays the current brick
    * Called by the browser or applet viewer to inform this JApplet that it
    * should start its execution. It is called after the init method and
    * each time the JApplet is revisited in a Web page.
     public void start()
         if(timer == null)
             timer = new Thread(this); // creates a new object of type Thread
             timer.start(); // starts the new thread
             running = true; // tells the program that the new thread is running
    * Runs the code that controls the animation
    public void run()
        do{
            repaint(); // redraws the screen
            try{
                timer.sleep(100); // puts the thread to sleep for 100 milliseconds
            } catch(InterruptedException e) {running = false;}
            // !!!!!!! have tried placing ball.start() here
        } while(running);
        timer = null; // destroys the timer thread
    * Called by the browser or applet viewer to inform this JApplet that
    * it should stop its execution. It is called when the Web page that
    * contains this JApplet has been replaced by another page, and also
    * just before the JApplet is to be destroyed.
    public void stop()
        running = false; // tells the program that the thread is now done
}These are the bits of code for my class heirarchy, just to (hopefully) make it easier to follow.
import java.awt.*;
* The parent class of all the games objects.
* @author Kris Nelson
* @version November 9, 2004
public class Sprite
    protected double screenX, screenY; // stores the x and y location of the object
    * Constructor for objects of class Sprite
    * @param xPosition   the initial x screen position
    * @param yPosition   the initial y screen position
    public Sprite(double xPosition, double yPosition)
        screenX = xPosition; // sets the initial x screen position
        screenY = yPosition; // sets the initial y screen position
    * Sets new x and y screen locations for an object
    * @param newX   the new x screen location
    * @param newY   the new y screen location
    public void setScreenXY(double newX, double newY)
        screenX = newX; // sets the new x screen location
        screenY = newY; // sets the new y screen location
    * Sends back the current x screen location
    * @return     the current x screen location
    public double getScreenX()
        return screenX; // returns the current x screen location
    * Sends back the current y screen location
    * @return     the current y screen location
    public double getScreenY()
        return screenY; // returns the current y screen location
import java.awt.*;
* Parent class of any game object that moves.
* @author Kris Nelson
* @version November 9, 2004
public class MovingSprite extends Sprite implements Runnable
     protected double speedX, speedY; // stores the speed of an object in the x and y directions
     protected Thread timer; // the thread which controls animation for all moving objects
     protected boolean running; // tells the program whether or not the thread is running
     * Constructor for objects of class MovingSprite
     * @param xPosition   the initial x screen position
     * @param yPosition   the initial y screen position
     * @param xSpeedValue   the speed in the x direction
     * @param ySpeedValue   the speed in the y direction
     public MovingSprite(double xPosition, double yPosition, double xSpeedValue, double ySpeedValue)
          super(xPosition, yPosition); // passes the initial screen positions to Sprite
          speedX = xSpeedValue; // sets the speed in the x direction
          speedY = ySpeedValue; // sets the speed in the y direction
     * Sends back the speed in the x direction
     * @return     the speed in the x direction
     public double getSpeedX()
         return speedX; // returns the speed in the x direction
     * Sends back the speed in the y direction
     * @return     the speed in the y direction
     public double getSpeedY()
         return speedY; // returns the speed in the y direction
     * Starts the thread in order to start animation
     public void start()
         if(timer == null)
             timer = new Thread(this); // creates a new object of type Thread
             timer.start(); // starts the new thread
             running = true; // tells the program that the new thread is running
     * Empty since the child objects have their own run methods
     public void run()
     * Stops the thread from running
     public void stop()
         running = false; // tells the program that the thread is now done
import java.awt.*;
* Creates a single ball who's purpose is to bounce around and destroy the bricks.
* @author Kris Nelson
* @version November 10, 2004
public class Ball extends MovingSprite
    protected static final double BALL_WIDTH = 15; // sets the width of the ball
    protected static final double BALL_HEIGHT = 15; // sets the height of the ball
    * Constructor for objects of class Ball
    * @param xPosition   the initial x screen position
    * @param yPosition   the initial y screen position
    * @param xSpeedValue   the speed in the x direction
    * @param ySpeedValue   the speed in the y direction
    public Ball(double xPosition, double yPosition, double xSpeedValue, double ySpeedValue)
        super(xPosition, yPosition, xSpeedValue, ySpeedValue); // passes the initial screen positions and ball speeds to MovingSprite
        // !!!!!!!! have tried placing timer.start() here
    * Displays a ball onto the screen
    * @param g   the Graphics object for this applet
    public void display(Graphics g)
        g.setColor(Color.blue); // sets the balls color
        g.fillOval((int)(screenX), (int)(screenY), (int)(BALL_WIDTH), (int)(BALL_HEIGHT)); // displays the ball
    * Runs the code that controls the balls animation
    public void run()
        do{
            try{
                timer.sleep(100); // puts the thread to sleep for 100 milliseconds
            } catch(InterruptedException e) {running = false;}
            screenX = screenX + speedX;
            screenY = screenY + speedY; // this is VERY SIMPLE BALL MOVEMENT FOR TESTING PURPOSES, WILL BE CHANGED LATER
        } while(running);
}Sorry if that was too much code. I'm just trying to make this easier to follow.
I placed a // !!!!!!!!!!!!! comment in the places where I have tried starting the ball thread.
So basically, everything is running fine, except that I'm not at all sure of where to start the ball Thread, and thus can't start anything moving. If someone could tell me where I should be starting the thread, I would REALLY appriciate it. Thank you :D
- Kris

Some advice.
1. the start method on the ball should be called from the start method on the applet and should in turn call the start method on the sprite's thread.
2. the run method of the Moveable sprite should have been declare abstract
3. don't implement borders manually. There's a java.awt.Border class for that.
4. probably, you don't want to have the game invoke each sprite by name; just make a big list of all the sprites and invoke all of them every time
5. do you really need provision for a non-circular ball? this isn't rugby.
6. I don't think you ever had a threading problem, just a display problem.
7. Don't write comments like this:     ball.display(g); // displays the ballHere's my (even more simplified version):import java.awt.*;
import javax.swing.*;
import java.util.*;
* Class BreakoutApplet - Plays a simple game of Breakout.
* @author Kris Nelson, modified by Michael Lorton
* @version November 10, 2004
public class BreakoutApplet extends JApplet implements Runnable {
    protected Ball ball;
    protected Paddle paddle;
    public boolean running; // tells the program whether or not the thread is running
    protected Thread timer; // the thread which controls the animation for the applet
    public void init() {
        // this is a workaround for a security conflict with some browsers
        // including some versions of Netscape & Internet Explorer which do
        // not allow access to the AWT system event queue which JApplets do
        // on startup to check access. May not be necessary with your browser.
        getRootPane().putClientProperty("defeatSystemEventQueueCheck",
                                        Boolean.TRUE);
         ball = new Ball(this, GAMEWIDTH / 2, GAMEHEIGHT / 2, 5, 5);
    public final static int GAMEWIDTH = 600;
    public final static int GAMEHEIGHT = 400;
    public void paint(Graphics g) {
        g.setColor(Color.lightGray);
        g.fillRect(0, 0,
                   GAMEWIDTH, GAMEHEIGHT);
        ball.display(g); // displays the ball
    * Called by the browser or applet viewer to inform this JApplet that it
    * should start its execution. It is called after the init method and
    * each time the JApplet is revisited in a Web page.
    public void start() {
        if(timer == null) {
            timer = new Thread(this); // creates a new object of type Thread
            timer.start(); // starts the new thread
            running = true; // tells the program that the new thread is running
        ball.start();
    * Runs the code that controls the animation
    public void run() {
        do{
            repaint(); // redraws the screen
            try{
                Thread.sleep(100);
            } catch(InterruptedException e) {running = false;}
        } while(running);
    public void stop() {
        running = false;
abstract class Sprite {
    protected double screenX, screenY; // stores the x and y location of the object
    protected final BreakoutApplet parent;
    * Constructor for objects of class Sprite
    * @param xPosition   the initial x screen position
    * @param yPosition   the initial y screen position
    public Sprite(BreakoutApplet parent, double xPosition, double yPosition) {
        this.parent = parent;
        screenX = xPosition; // sets the initial x screen position
        screenY = yPosition; // sets the initial y screen position
    * Sets new x and y screen locations for an object
    * @param newX   the new x screen location
    * @param newY   the new y screen location
    public void setScreenXY(double newX, double newY) {
        screenX = newX; // sets the new x screen location
        screenY = newY; // sets the new y screen location
    * Sends back the current x screen location
    * @return     the current x screen location
    public double getScreenX() {
        return screenX; // returns the current x screen location
    * Sends back the current y screen location
    * @return     the current y screen location
    public double getScreenY() {
        return screenY; // returns the current y screen location
    abstract public void display(Graphics g);
* Parent class of any game object that moves.
* @author Kris Nelson
* @version November 9, 2004
abstract class MovingSprite extends Sprite implements Runnable {
    protected double speedX, speedY; // stores the speed of an object in the x and y directions
    protected Thread timer; // the thread which controls animation for all moving objects
    protected boolean running; // tells the program whether or not the thread is running
    * Constructor for objects of class MovingSprite
    * @param xPosition   the initial x screen position
    * @param yPosition   the initial y screen position
    * @param xSpeedValue   the speed in the x direction
    * @param ySpeedValue   the speed in the y direction
    public MovingSprite(BreakoutApplet parent,
                        double xPosition, double yPosition,
                        double xSpeedValue, double ySpeedValue) {
        super(parent, xPosition, yPosition);
        speedX = xSpeedValue; // sets the speed in the x direction
        speedY = ySpeedValue; // sets the speed in the y direction
    * Starts the thread in order to start animation
    public void start() {
        if(timer == null) {
            timer = new Thread(this); // creates a new object of type Thread
            timer.start(); // starts the new thread
            running = true; // tells the program that the new thread is running
    * Runs the code that controls the balls animation
    public void run() {
        while (parent.running) {
            try{
                Thread.sleep(100);
            } catch(InterruptedException e) {
                System.err.println(e);
            step();
    abstract protected void step();
* Creates a single ball whose purpose is to bounce around and destroy the bricks.
* @author Kris Nelson
* @version November 10, 2004
class Ball extends MovingSprite {
    protected static final int BALL_DIAMETER = 15;
    * Constructor for objects of class Ball
    * @param xPosition   the initial x screen position
    * @param yPosition   the initial y screen position
    * @param xSpeedValue   the speed in the x direction
    * @param ySpeedValue   the speed in the y direction
    public Ball(BreakoutApplet parent,
                double xPosition, double yPosition,
                double xSpeedValue, double ySpeedValue) {
        super(parent, xPosition, yPosition, xSpeedValue, ySpeedValue);
    * Displays a ball onto the screen
    * @param g   the Graphics object for this applet
    public void display(Graphics g) {
        g.setColor(Color.blue);
        g.fillOval((int)(screenX),
                   (int)(screenY),
                   BALL_DIAMETER, BALL_DIAMETER);
    protected void step() {
            screenX = screenX + speedX;
            if (screenX < 0) {
                screenX = -screenX;
                speedX = -speedX;
            else if ((screenX + BALL_DIAMETER)> BreakoutApplet.GAMEWIDTH) {
                screenX = 2*(BreakoutApplet.GAMEWIDTH - BALL_DIAMETER) - screenX;
                speedX = -speedX;
            screenY = screenY + speedY;
            if (screenY < 0) {
                screenY = -screenY;
                speedY = -speedY;
            else if ((screenY + BALL_DIAMETER) > BreakoutApplet.GAMEHEIGHT) {
                screenY = 2*(BreakoutApplet.GAMEHEIGHT - BALL_DIAMETER) - screenY;
                speedY = -speedY;
}

Source2wsdd: ServiceGen does not contain a start method - help!

Hello all Weblogic Users!
I would greatly appreciate any help with this problem.
I am getting this error when I do my build on Linux.
[source2wsdd] source2wsdd: Doclet class weblogic.webservice.tools.ddgen.ServiceGen does not contain a start method.
Previously I was getting an error where the ServiceGen class could not be found. This was occuring both in Windows and Linux.
For Windows, this can be fixed in two ways. 1) Run setWLSEnv.cmd first (in weblogic81/server/bin. 2) (Unconfirmed but try it) Add the tools.jar, weblogic.jar, and webservices.jar to the ant runtimes lib in Eclipse (see preferences/ant/runtimes/global entries. - This will let you run the task inside Eclipse)
In Linux, I added the webloigc.jar and webservices.jar to the user's special ~/'.ant/lib directory (see ant documentation). This too fixed the problem of being unable to find the ServiceGen class. But now I am getting the error above. I am ripping my hair out trying to fix it.
Any help would be appreciated.
Thanks to all....

Hi bkshn,
This error is caused by the missing "Main" method in your project. it is the entry point of your project.
If you want to create a EF project, you could follow the way in the aricle below.
https://msdn.microsoft.com/en-us/data/ee712907#codefirst
The Main method is like below.
class Program
static void Main(string[] args)
using (var db = new BloggingContext())
// Create and save a new Blog
Console.Write("Enter a name for a new Blog: ");
var name = Console.ReadLine();
var blog = new Blog { Name = name };
db.Blogs.Add(blog);
db.SaveChanges();
// Display all Blogs from the database
var query = from b in db.Blogs
orderby b.Name
select b;
Console.WriteLine("All blogs in the database:");
foreach (var item in query)
Console.WriteLine(item.Name);
Console.WriteLine("Press any key to exit...");
Console.ReadKey();
And you could start to learn the EF from the following MSDN blogs.
https://msdn.microsoft.com/en-us/data/ee712907
If you have any other concern regarding this issue, please feel free to let me know.
Best regards,
Youjun Tang
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Photo Gallery start up problem

I have a glitch and it's probably me … but here's what
I know.
About Don Booth's Photo Gallery:
It's great. Everything is good - integrated with my CSS -
looks nice.
When the page loads all is well except the first image in the
Gallery does not display in <div id="mainImageOutline"... (and
the first thumbnail is not highlighted). While I'm building and
testing this is OK. Just click a thumbnail and everything works
well.
In the demo, the Gallery is operational by default and starts
up with the first thumbnail and Spry:detail produces the
corresponding image (automatically). That's what I want.
About my code:
Except for a couple of "page layout" divs that I have,
consistent with my own site-wide style sheet conventions, such as
<div id="wrapper"> and <div id="maincontent"> I have:
1. Copied Don Booth's xhtml code directly from the
Spry_1_1_022408 download sample.
2. Copied Don Booth's css code directly from the same
download sample.
3. Copied Don Booth's gallery.js directly (without change as
far as I know).
The only significant change (apart from CSS and xhtml
structure) in my work is - I added an additional Spry:detail div to
present additional datapoints from xml. This is not relevant to my
question because the issue that concerns me is consistent if I
remove this second detail div. The start-up problem remains.
The URL for the gallery page in question is:
http://www.yhqg.org/Celebration/quiltshow2008/galleryix/gallery.htm
I imagine the problem is in gallery.js. You should know that
javascript is a bit like dungeons and dragons to me.
I have an error report:
Error: dsPhotos is not defined
Source File:
http://www.yhqg.org/Celebration/quiltshow2008/galleryix/includes/gallery.js
Line: 55
So, when I see:
var gAutoStartSlideShow;
if (gAutoStartSlideShow == undefined)
gAutoStartSlideShow = true;
I imagine I'm looking at something useful but I don't know
what to do with it, or if it is the right code to focus on. I
respect the relationship with level 4 support engineers, but after
trying to solve my own issue for a few weeks I decided it was time
to submit my question. How do I get Photo Gallery to start up like
the demo?
Additional information:
There is also a series of error reports that show when the
Gallery is playing (for example):
Warning: Expected end of value for property but found
'-0.0775'. Error in parsing value for property 'opacity'.
Declaration dropped.
Source File:
http://www.yhqg.org/Celebration/quiltshow2008/galleryix/gallery.htm
Line: 0
I don't think it is related, but that's what I know.
I tried to copy my xhtml (below) but it caused this message
to exceed allowed size. But I don't see that xhtml is the problem.
You can see the source at the URL (above).

Hi Latauro,
Sounds like you need to turn your Slideshow into a Track, and then set the Track to display as 16:9 Letterbox; but first, you'll also need to encode your slides as wide Mpeg 2 clips (encode set to 16:9), too; to whatever duration you have them set in the Slideshow, currently (if they're not already wide encoded clips).
It would be good to stick some same duration audible or silent same format and bit rate audio underneath each of the new movie slides, to present players a nicely packed VOB.
Take care,
Trai Forrester
TFDVD Research Labs
http://www.DVDVerification.com
PS. If this helps you, would you please remember to declare the thread as "Solved". Although probably hopeless, someone should make a run to try and catch up with good Drew!! (see what happens Hal, when you take some time off?!

How to throw Exception in Thread.run() method

I want to throw exception in Thread.run() method. How can I do that ?
If I try to compile the Code given below, it does not allow me to compile :
public class ThreadTest {
     public static void main(String[] args) {
     ThreadTest.DyingThread t = new DyingThread();
     t.start();
     static class DyingThread extends Thread {
     public void run() {
     try {
               //some code that may throw some exception here
          } catch (Exception e) {
          throw e;//Want to throw(pass) exception to caller
}

(a) in JDK 1.4+, wrap your exception in RuntimeException:
catch (Exception e)
throw new RuntimeException(e);
[this exception will be caught by ThreadGroup.uncaughtException() of this thread's parent thread group]
In earlier JDKs, use your own wrapping unchecked exception class.
(b) if you know what you are doing, you can make any Java method throw any exception using Thread.stop(Throwable) regardless of what it declares in its "throws" declaration.

Calling thread.start() more than once concurrently

Hi, I got a simple doubt that may feel awkward or absurd to people who are well versed in the java threading concepts. I just thought of it and as I couldn't get an easy answer I am posting this.
Consider a class that implements the runnable interface. The run() method of the class is implemented with just a System.out.println(). If I make an instance of this class, say 't' in the main method and calling t.start() susequently twice or thrice; an illegal ThreadStateException will be thrown. The code snippet is as follows:
ThreadTest t = new ThreadTest();
t.start();
t.start();
It is understood that state of the thread object is changed to run state and so, if it is again started, it must be thrown. So if I put a Thread.sleep() inbetween these two subsequent calls assuming that the main method thread will be sleeping. So there is sufficient time for the first thread to terminate and then only the second will start - still the same exception is being thrown. I tried putting the synchronized qualifier for run too, still no effect - the same only happening. Why the java thread object is made in such a way that once the thread changes it state from Runnable to Running and then finally to dead state, it can be restated back to Runnable state, such that the start() method can be called again. Is it possible or not? Please post your comments.

As ejp says you can't start a thread more than once - even if it has already terminated after the first start.
By making threads a one-shot it simplifies reasoning about them: you don't have to wonder whether a second start() will work or not, depending on whether the thread has completed its first "incarnation". It also makes it easier to ensure thread resources are reclaimed. It also avoids semantic issues like whether anything about the thread is "carried over" across incarnations.
This might seem a limitation but there are many ways around it - simply don't let the thread terminate. Whatever control structure you would enforce by re-starting the thread can be emulated without letting the thread terminate in between "executions".

Can start method invoke twice at one instance

I am using JBoss and writing a class which extends Thead. I would like to ask can I invoke start() method twice to an instance of that class. I've tried it but it seems that the object did nothing when start() method is invoked at the second time.

Any Thread can only be start()ed once.
Also, prefer implementing Runnable to extending Thread. Think of Threads as the workers and Runnables as the job itself. You implement Runnable because your "unit of work" or whatever you want to call it IS-A Runnable -- that is, something that will do its job start-to-finish when you call run. You would only extend Thread if your class IS-A Thread -- that is, it has a reason to do everything Thread does, and you need to slightly add to or modify Thread's behavior.

Rather complicated (possibly!) threading/event handling problem...

OK, so here's a good question to ask for my first post to this site!
My current "project" is a GUI applet that does real-time interactions on a set of objects and user input. I'm using double buffering, event handling (from the keyboard) and multiple threads to handle the categories of "user input and graphics" and "world state updating." Here is a rough overview of how the program is layed out:
// keyboard input status class
class Keyboard extends KeyListener {
   static int[] code = new int[7];            // contains keycodes of interesting keys
   static boolean[] status = new boolean[7];     // status of keys (true=pressed)
   static boolean getStatus(int key) {
      return status[key];
   void keyPressed(KeyEvent e) {
      for(int i = 6; i >= 0; i--)
         if(code[i] == e.code)
            status[i] = true;
   void keyReleased(KeyEvent e) {
      for(int i = 6; i >= 0; i--)
         if(code[i] == e.code)
            status[i] = false;
// main program applet
class Program extends Applet implements Runnable {
   static Thread thread;      // main thread of applet
   static Image buffer;         // double buffer for offscreen rendering
   static boolean running; // flag to indicate status of applet
   void init() {
      buffer = createImage(500, 500);
      // other initializations
   void destroy() {
      // other disposes
   void start() {
      running = true;
      thread = new Thread(this);
      thread.start();
      addKeyListener(new Keyboard());   // begin receiving input
   void stop() {
      running = false;
      if(thread != Thread.currentThread())
         thread.join();    // wait for thread to die before continuing
   void run() {
      double paintTimer = 0;   // timer to suspend painting to buffer until necessary
      double dt = 0;       // difference in time between loops
      while(running) {
         // update timing stuff (dt and paintTimer)
         // update world status
         paintTimer -= dt;      // to decrement painting timer
         if(paintTimer <= 0) {
            paintTimer = 1.0 / fps;    // reset paint timer based on current fps setting
            synchronized(syncObject) {
               // paint world to buffer
               repaint();
         Thread.yield(); // to yield time to painting and user input thread
   // this method is only called by the internal thread within the applet
   // that is responsible for painting and event handling
   void paint(Graphics g) {
      // make sure painting to screen won't conflict with thread that's drawing on buffer!
      synchronized(syncObject) {
         g.drawImage(buffer, 0, 0, null); // do double buffering...paint buffer to screen
}So the end result is that it works fine some of the time, but every once in awhile I'll get these strange results where it'll seem as if the internal thread that handles graphics and input will get bogged down or stop responding normally, even with the Thread.yield() call from the main applet thread. I'll get results where the world will continue to be updated correctly, but the user input and onscreen rendering freeze in a particular state for a matter of seconds, and then it seems to regain control for a brief few milliseconds (hence I'll get a quick screen refresh and keyboard state change), and then it'll freeze again. Once this starts happening somewhere in the middle of execution, it continues to happen throughout that runtime session. Sometimes when I force-close the appletviewer I'll get weird native runtime exceptions that seem to occur within Sun's keyboard input manager.
Almost always it'll run perfectly for many minutes, and then all of a sudden it'll start to freeze up. Every once in awhile it freezes almost immediately after startup. I've run some testcases on it and am pretty confident it has nothing to do with the synchronization or the fact that I create a new applet thread every time the applet is restarted dynamically. Is it something happening within the event thread of the applet that I'm not aware of? Or is it something wrong with the flow of my code? Thanks for any input or help you can give! I'll be happy to send more details if needed.
Zach

right before your repaint, putSystem.out.println("Is EDT? "+SwingUtilities.isEventDispatcherThread());if its printing false, then you need to do SwingUtilities.invokeLater( ... );
and put GUI updating code in the invoke later.

Thread start() method problem

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