A question about thread!(help a chinese learner)

package thead;
import javax.swing.UIManager;
import java.awt.*;
class mythread implements Runnable {
int i;
String name;
mythread(String nn){
i=0;
name=nn;
public void run(){
System.out.println("name"+"starting!");
try{
do{
Thread.sleep(1000);
System.out.println("IN"+name+"the count is"+i);
i++;
while(i<10);
catch(InterruptedException wwwww){
System.out.println("interrupt");
class use {
public static void main(String[] args) {
System.out.println("starting");
mythread pp=new mythread ("ok");
Thread ww=new Thread(pp);
ww.start();
do{
System.out.print(".");
try{
Thread.sleep(100);
catch(InterruptedException wwwww){
System.out.println("interrupt");
while(pp.i!=10);
System.out.println("ending");
Why the result is :
starting
.okstarting!
.......INokthe count is0
....INokthe count is1
..........INokthe count is2
...........INokthe count is3
........INokthe count is4
....INokthe count is5
....INokthe count is6
............INokthe count is7
...........INokthe count is8
..........INokthe count is9
ending
i can not really understood
is this about my machine?

Hmm i was trying your code on my machine and the output was:
starting
.namestarting!
.........INokthe count is0
..........INokthe count is1
..........INokthe count is2
..........INokthe count is3
..........INokthe count is4
..........INokthe count is5
..........INokthe count is6
..........INokthe count is7
..........INokthe count is8
..........INokthe count is9
ending
so i guess something's wrong with your vm/os/machine.

Similar Messages

Dumb question about Thread Safety in Servlets

Hi all
I wrote this Client API for sending requests and receiving responses to / from a multivalue database. The API is called by my Servlet. Now it seems my API is not thread safe because when several people open up the servlet at the same time, the API gets totally confused. When the API calls are inside a synchronized(){} it works just fine, but obviously at a big performance hit. Is that the wrong way of doing it??
However when I was doing the ACID test locally on my machine, by opening two command prompts and excuting the same java program (with the same code in it as the servlet, but standalone) my API worked just fine. How come?
Any insights appreciated as I am just learning about thread safety now (the hard way :-( )
cheers
Dejan

Does this help
Are you using one connection to the database shared by all instances
of your servlet
And is this connection create in the init method of the servlet and stored
in the servlet context.
Problem 4 people try and use your servlet at the same time, each servlet trys to
create a connection to the database and then store it in the servlet context and
this causes a problem.
Solution create a listener to create the connection and store it in the servlet context
when the servlet is created.
If this is your problem it is not advisable to use only one connection to the db
try using db pooling

Challanging question about Threads. Can anyone help?

Hello,
I've been learing how to use threads and I have run into a little rut. I am making a game that listens for clicks of the mouse on the board AND allows people to talk to each other in a chat box.
I've made a chatThread and in the public void run() method I can do the following...
public void run(){
while(true){
try{
chatText.append(ServerIn.readLine()+"\n");
catch (Exception h){}
this pastes whatever the other person wrote into the public chattext area. now my problem is this. I need another thread that listens for button clicks. If the button is clicked on one side, the other side needs to be able to read that click and perform a certan task. I only have 1 thread running, but I have made an instatance of PrintWriter for the text and DataInputStream for the integer value. I have tried things like this and they really don't like me. (they cause faluts and whatnot)
public void run(){
while(true){
try{
chatText.append(ServerIn.readLine()+"\n");
ServerIn2a.readInt();
catch (Exception h){}
Sometimes the integer will read into the ServerIn2a and then when i try to chat it can't read into the ServerIn varialble.
Do I need to make two seperate thread and somehow pause one and run one, then pause the other?
Thanks for your help!

Ok, sorry, here is a better description of what my program looks like (the parts that concern this topic)...
public class Game extends JApplet implements ActionListener, Runnable{
PrintWriter ClientOut = null; // to send messages to the server
BufferedReader ClientIn = null; // to receive messages from the server.
PrintWriter ServerOut = null; // to send messages to the client
BufferedReader ServerIn = null; // to receive messages from the client.
DataInputStream ClientIn2a = null; // to send messages to the server
DataOutputStream ClientOut2a = null; // to receive messages from the server.
DataInputStream ServerIn2a = null; // to send messages to the client
DataOutputStream ServerOut2a = null; // to receive messages from the client.
//On the main screen, if they press the "host" button they become the host and the this happens.....
//I want these two lines to read text from a dialog box and then pass that text to the other person      //playerinput from a dialog box so it can be passed
ServerIn = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
ServerOut = new PrintWriter(clientSocket.getOutputStream(),true);
//When they click on a button, I am trying to read the buttons coordinate which will be a Integer value. I //I want to get that integer value to the other person so I make these DataInput and Output variables.
ServerIn2a = new DataInputStream(clientSocket.getInputStream());
ServerOut2a = new DataOutputStream(clientSocket.getOutputStream());
//now I made a thread that is always supposed to listen to perform the action of sending the text to
//the appropriate text listener and to send the integer to the appropriate DATAINPUT listener.
Thread ServerThread = new Thread(this)
ServerThread.start();
//on the main screen, if they press the client button......
ClientIn = new BufferedReader(new InputStreamReader(serverSocket.getInputStream()));
ClientOut = new PrintWriter(serverSocket.getOutputStream(),true);
ClientIn2a = new DataInputStream(serverSocket.getInputStream());
ClientOut2a = new DataOutputStream(serverSocket.getOutputStream());
//now I made a thread that is always supposed to listen and perform the action to send the data to the
//other person
Thread clientThread = new Thread(this);
clientThread.start( );
//here is the actionPerformed method. They press enter in the text area box and this gets run.....
if(player==1){
//THE TEXT THEY TYPE FIRST GETS PASTED INTO THEIR OWN CHAT AREA
     chatText.append(HostUserName+": " + messageField.getText() + "\n");
     //NOW I WANT TO SEND WHEY THEY TYPE TO THE OTHER PERSON
try{
ServerOut.write(HostUserName+": " + messageField.getText()+"\n");
ServerOut.flush(); }
catch(Exception e){Mbox.showMessageDialog(null,"Chatting error","connect",1);}
//here is my run method (this is where I think I am having my problems and that I need help with.
public void run(){
     if(player == server){
     while(true){
     try{
     //THIS IS WHERE THE INTEGER SHOULD BE READ INTO
               performAFucntion(ServerIn2a.readInt());}
          catch(Exception h){}
          //THIS TRY STATEMENT IS WHERE THE TEXT SHOULD BE READ
     try{
          chatText.append(ServerIn.readLine()+"\n"); }
     catch (Exception h){}
//ELSE YOU ARE THE OTHER PERSON AND YOU DO THE EXACT OPPOSITE OF ABOVE
OK! Now that the code is out of the way. My problem.... Sometimes when I click on a button, the ineger value gets assigned to the ServerIn.reasline and funny symbols pop up in the other persons text area. And then when I try to type text in my text box after I get the wierd symbols into my chat text area, the CATCH (Exceptoin E) from my actionPerformed function that deals with sending the text gets activated and I see the dialog box that tells me there was an error.
I THINK my error is in my run statement. I think everytime I write something, wether it be an integer or a text, the first .READLINE( ) that gets encountered in my run statement reads it. I think I have to have the WHILE(TRUE) statement or else it wont continuoulsy try to read in data.
Can anyone tell me if I need to somehow make two threads, one that listens for the text and a seperate one that listens for the integer value?
I hope this is a little bit more clearer than my last letters. Thanks for being patient with me.

Questions about thread priority...

Situation 1) setPriority(int adsa)
public class ThreadPrioDemo1 {
      static class Demo1 implements Runnable{
      public void run(){ //blablabla}
     public static void main(String[] asdf){
          Runnable r = new Demo1();
          Thread myThread = new Thread(r);
          Thread mainT = Thread.currentThread();
          //mainT's priority is 5, so as myThread.
        mainT.setPriority(10);
//mainT's priority to MAX, this simultaneously changes myThread to 10 as well.
        //or
        myThread.setPriority(10);
//myThread priority to MAX, however, this does not change mainT to 10
}Question 1), why if main Thread is set to a certain priority, the thread it creates automatically change its priority to the same as well, but the reverse is different??
Situation 2) this is slightly more complex
public class ImplementingRunnable {
     public static void main(String[] args) {
     Thread mainT = Thread.currentThread();
          for(int ii=0 ; ii<args.length ; ii++) {
               Runnable r = new MyRunnable(args[ii]);
               Thread t = new Thread(r);
            t.setDaemon(true);
            //t.setPriority(Thread.MAX_PRIORITY);
               t.start();
}and
public class MyRunnable implements Runnable {
    public void test(){
    System.out.println("test");
     String message;
     public MyRunnable(String msg) {
          message = msg;
     public void run() {
          Thread me = Thread.currentThread();
          try {
               for(int ii=0 ; ii<10 ; ii++) {
                   //case (1) me.setPriority(Thread.MIN_PRIORITY);
                    me.sleep(3);
                    System.out.println(message);
                    //case (2) me.setPriority(Thread.MIN_PRIORITY);
          } catch (InterruptedException ie) {
}In class ImplementingRunnable, how is the commented code line related or counter-related with the commented case 1 code line in MyRunnable??
Please help
thanks

Let me speak my question again very simply:
1)
Say I have two threads, 1 is main() thread, the program entry point, 2 is another thread created by main().
Now, the default priority for both two is 5. If I change the priority for main() to a certain level, the other thread created by it automatically change its priority to the same level? why? and however, the reverse (in this case, if I change the priority for the thread created by main()) is not.
2)
public class Demo{
static class MyThread implements Runnable{
public void run(){//some thing}
Thread t = new Thread(this);
t.setPriority(10);
public static void main(String[] afd){
Runnable r = new MyThread();
Thread t1 = new Thread(r);
t1.setPriority(1);
}What can you say about both bold code lines?
If I use println() to track the Priority, the final priority, that is, t1, is 1. It is logical, however, the program behaves differently without the bold code line in the static class MyThread, despite the final priority for t1, is the same, 1.
Any help by now??
thanks alot

I'm a newbie: I have a question about threads

midp 2.0
Java SE 5.0
J2ME version 2.2
Below is my code I'm stucked with..... The code here shows a midlet class
and another class derived from Thread (NetworkThread). This NetworkThread
gets started from the main midlet... Search my code for the term ??????? and
there you find my trouble area... What I'm having trouble with is that at
that point in my code a NetworkThread has been given a url to access, and
putting network access in the main thread is a bad thing because one can
never know how long it takes to access the server... I want this line:
System.out.println("NETWORK COMMINUCATION DONE"); to be processed after
NetworkThread is done requesting the url.... I'm not sure how to solve this
code so that the midlet waits for NetworkThread to access the url... But
while NetworkThread access the url I want the midlet to response to user
input, I don't want it to look like the midlet has crashed......
Any tips on how I can solve this issue will be greatly appreciated...
By the way, if you see anything else that could have been improved in my
code, then please tell me about it too....
MY CODE:
NETWORKTHREAD:
package com.test;
import java.io.IOException;
import java.io.*;
import java.util.*;
import javax.microedition.io.*;
public class NetworkThread extends Thread
private boolean networkStop;
private boolean networkPause;
private HttpConnection httpConnection = null;
private InputStream inputStream;
private String Url;
private String netCommand = null;
private String netArg = null;
private LoginForm loginForm;
public NetworkThread(String serverURL)
Url = serverURL;
synchronized void requestStop()
networkStop = true;
notify();
synchronized void resumeGame()
networkPause = false;
notify();
synchronized void setCommand(String cmd, String arg)
System.out.println("setCommand = " + cmd);
netCommand = cmd;
netArg = arg;
networkPause = false;
notify();
void pauseThread()
networkPause = true;
public void run()
networkPause = true;
networkStop = false;
while (true)
   if (networkStop) {
    break;
   synchronized(this) {
    while (networkPause) {
     try {
      wait();
     catch (Exception e) {}
   synchronized(this) {
     if (netCommand != null) {
       if (netCommand.equals("LOGIN")) {
         //Here some networking processing will
         //be done
     else if (netCommand.equals("LOGOUT")) {
     netCommand = null;
   pauseThread();
THE MIDLET:
package com.test;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.IOException;
import java.lang.String;
public class Test extends MIDlet
private Display display;
private NetworkThread networkThread;
private String Url;
public Test() {
    display = Display.getDisplay(this);
public void startApp() throws MIDletStateChangeException {
    if (networkThread == null) {
      networkThread = new NetworkThread(Url);
      networkThread.start();
else {
     networkThread.start();
public void destroyApp(boolean unconditional) throws
MIDletStateChangeException {
   public void pauseApp() {
   public void commandAction(Command c, Displayable s) {
     if (c == okCommand) {
       networkThread.setCommand("LOGIN", "arg1");
       System.out.println("NETWORK COMMINUCATION DONE");
}

You will probably need to learn about HTTP and XML to complete this project. If you don't know Java at all then I would suggest starting with tutorials like these ones first
http://java.sun.com/docs/books/tutorial/index.html
Have a happy day.

A question about threads

Hi to everybody,
I'm learning Java and I would like to know what's the difference between extending the Thread class and implementing the Runnable interface.
Why when I run two objects that are instances of a Runnable class they seem to
run concurrently, while when I run two objects whose class extends Thread, the virtual machine first executes the first thread , and only when the first thread has died it executes the second (the two threads have the same priority).
I would also apreciate some clarifying information about "time-slicing" and the use of the method Thread.yield();
thanks

Main factor what desides whether to extend Thread or
Implement Runnable is do you want to extend another.Sorry to say this but: WRONG!
The main factor in a decision like this should be your model, i.e. is the class you are modelling really a sub-class of Thread, or - more likely - is it a task that should be able to run (on a thread or otherwise)?
If you are in fact implementing a new kind of Thread (i.e. YourClass is-a Thread), then you extend Thread, otherwise you should implement Runnable.
Ex:- If your class need to Extend another class then
you cant extend Thread so you have to use Runnable.This is true, of course, but it should be done for the right reasons.
So: implement Runnable (unless you are implementing a new kind of Thread)

A question about thread safety and the Acrobat SDK

Hi All,
On page 12 of this FAQ: http://www.adobe.com/devnet/acrobat/pdfs/Acrobat_SDK_developer_faq.pdf
It says that Use of any Acrobat product in a multithreaded way is technically impossible.
I'm currently writing a command line application to perform some basic data gathering on a PDF file. The Application only makes use of a PDDoc object, and never calls on any other kind of object (i.e. AVDoc).
The application itself is not multithreaded. All of the logic runs in a single thread.
However, the application will be called (via the command line) from another application that /is/ multithreaded. I think that this might be fine, but I wasn't sure. In this case, would this count as a single thread, but spread across multiple processes? And if that is the case, would that be OK with the SDK?
Or would having multiple invocations/calls into the Acrobat DLLs cause the same issue as a multi-threaded application?
Unfortunately, I haven't done a lot of work with threads before. This might be a very silly question.

The application would be called from a perl script that is used to automate several tasks. The app is a console application, written in C# w/ the Acrobat COM components, and Visual Studio 2005.
The console application uses the Acrobat SDK to instantiate a PDDoc object, open a PDF, and get information about the document. It then returns results back to the console.
So, the perl script just calls: "C:\pdfinfo.exe -f=myPdf.pdf" and pipes the result to a log file.
In this case, it never creates a new instance of the Acrobat application, but it does use the SDK.
The reason that I was concerned was that the perl script is multi-threaded. I wasn't sure if acrobat was just sensitive to multiple threads inside a single process, or if it was unable to handle multiple processes as well.
PDL's answer suggests that I should be fine as long as a new process is started each time. This is good to hear.

A question about thread

i am learning up on threads.
A Java program can have many threads, and these threads can run concurrently, either asynchronously or synchronously.
so lets say i have 2 classes, A and HelloThread
A
public class A {
     public static void main(String[] args) throws IOException {
        //(lots of codes)
}HelloThread
public class HelloThread extends Thread {
    public void run() {
        System.out.println("Hello from a thread!");
    public static void main(String args[]) {
        (new HelloThread()).start();
}this is what i am confused.
both classes have public static void main(), is that possible?
if no, then what command makes the thread run concurrently?
(since it says many threads can run concurrently)
i m soo confused.
tq

When you run a Java program the java command gives the name of the main class. The interpretter looks in the class you name for a main() method. There's nothing special about the method, appart from it being used this way. It doesn't matter if there are identical methods in other classes because you tell the interpretter which one to look in.
By the way, it's not good practice to subclass Thread this way. To run code in a Thread, create a class (or, very often and anoymous class object) which implements Runnable and use the Runnable object in the constructor of Thread.

Question about awarding "helpful" stars

One of my questions was just answered, and I wanted to award two "helpful" stars and one "solved" star. Evidently I didn't really understand how this works, because once I awarded the "solved" star, it wouldn't allow me to award the other "helpful" star, which I felt the third person in the thread deserved. I tried marking the message as "unsolved", but that didn't help. Is there any way to go back and award the last "helpful" star?

Thanks for all the responses!
Last night I went over the entire thread repeatedly looking for a way to mark the last "helpful", and the "helpful" option was simply not available on any of the responses. It just wasn't there, and I couldn't find any way to get it to appear. I actually spent quite a bit of time scrolling up and down the thread looking for the "helpful" option.
However, I just went back to check again, and the "helpful" option has now appeared on 3 responses. So the answer seems to be that I CAN go back and award a "helpful" star after awarding a "solved" star, but for whatever reason, I can't do it immediately?
So evidently that problem wasn't a problem after all--just me messing up somehow. The stars can in fact be awarded in any order. But I think I'll try awarding the green one last after this so I can do them all at once.
Thanks everybody for all your help. Now on to the hard part--awarding the stars. Sometimes I wish I could turn the green one into two gold ones so I could award them to more people. So often the solution does not come from just one person, but from many. Like on this thread--it will probably have to be arbitrary who gets what, but I am equally grateful to all of you, and I greatly appreciate it that you took the time to help me.
Again, many thanks!

Urgent question about Thread-safety

Hi all,
the new tiger release provides an "isReachable()" method for the "InetAddress" object.
I've found, this method is not thread-safe (see the source and output below).
It returns true for all threads, when multiple threads using this method with different adresses are running at a time and one of the addresses is reachable. This happens only on WinXp. Running on Linux, the output is like expected.
I've tried to report this as a bug. But the gurus answered, taking care of thread safety would be a "programmers task".
My question is, what can I do, to be thread-safe in my case?
W.U.
import java.util.*;
import java.net.*;
public class IsReachableTest_1 extends Thread{
    static volatile int inst=1;
    static final String NET_ADDR="192.168.111.";
    int instance=inst++;
    public void run(){
        for(int i=19;i<23;i++){
            try{
                long start=System.nanoTime();
                if(InetAddress.getByName(NET_ADDR+i).isReachable(1000))
                    System.out.println(""+instance+"--host found at:"+NET_ADDR+i+"--time:"+(System.nanoTime()-start)/1000000);
                else
                    System.out.println(""+instance+"--no host at:"+NET_ADDR+i);
            }catch(Exception e){System.out.println(""+instance+"--ERROR "+e.toString());}
        System.out.println(""+instance+"--done.");
    public static void main(String[] args) {
        System.out.println(
            System.getProperty("java.vendor")+" "+
            System.getProperty("java.version")+" running on "+
            System.getProperty("os.name")+" "+
            System.getProperty("os.version"));
        Vector v=new Vector();
        System.out.println("\nTest 1: One after another:");
        for(int i=0;i<10;i++){
            IsReachableTest_1 t;
            t=new IsReachableTest_1();
            t.start();
            try{
                t.join();
            }catch(Exception e){System.out.println("MAIN1: "+e.toString());}
        System.out.println("\nTest 2: All together:");
        inst=1;
        for(int i=0;i<10;i++){
            IsReachableTest_1 t;
            t=new IsReachableTest_1();
            t.start();
            v.addElement(t);
        for(Iterator i=v.iterator();i.hasNext();)
            try{
                ((IsReachableTest_1)i.next()).join();
            }catch(Exception e){System.out.println("MAIN2: "+e.toString());}
            System.out.println("\nALL DONE");
And here is the output, when running on WinXp:
Sun Microsystems Inc. 1.5.0-beta running on Windows XP 5.1
Test 1: One after another:
1--no host at:192.168.111.19
1--no host at:192.168.111.20
1--host found at:192.168.111.21--time:2
1--no host at:192.168.111.22
1--done.
2--no host at:192.168.111.19
2--no host at:192.168.111.20
2--host found at:192.168.111.21--time:4
2--no host at:192.168.111.22
2--done.
3--no host at:192.168.111.19
3--no host at:192.168.111.20
3--host found at:192.168.111.21--time:1
3--no host at:192.168.111.22
3--done.
4--no host at:192.168.111.19
4--no host at:192.168.111.20
4--host found at:192.168.111.21--time:1
4--no host at:192.168.111.22
4--done.
5--no host at:192.168.111.19
5--no host at:192.168.111.20
5--host found at:192.168.111.21--time:3
5--no host at:192.168.111.22
5--done.
6--no host at:192.168.111.19
6--no host at:192.168.111.20
6--host found at:192.168.111.21--time:1
6--no host at:192.168.111.22
6--done.
7--no host at:192.168.111.19
7--no host at:192.168.111.20
7--host found at:192.168.111.21--time:1
7--no host at:192.168.111.22
7--done.
8--no host at:192.168.111.19
8--no host at:192.168.111.20
8--host found at:192.168.111.21--time:1
8--no host at:192.168.111.22
8--done.
9--no host at:192.168.111.19
9--no host at:192.168.111.20
9--host found at:192.168.111.21--time:1
9--no host at:192.168.111.22
9--done.
10--no host at:192.168.111.19
10--no host at:192.168.111.20
10--host found at:192.168.111.21--time:1
10--no host at:192.168.111.22
10--done.
Test 2: All together:
1--no host at:192.168.111.19
2--no host at:192.168.111.19
3--no host at:192.168.111.19
4--no host at:192.168.111.19
5--no host at:192.168.111.19
6--no host at:192.168.111.19
7--no host at:192.168.111.19
8--no host at:192.168.111.19
9--no host at:192.168.111.19
10--no host at:192.168.111.19
2--no host at:192.168.111.20
3--no host at:192.168.111.20
6--host found at:192.168.111.20--time:924 <----- this host does not exist!!
5--host found at:192.168.111.20--time:961 <----- this host does not exist!!
10--host found at:192.168.111.20--time:778 <----- this host does not exist!!
9--host found at:192.168.111.20--time:815 <----- this host does not exist!!
2--host found at:192.168.111.21--time:37
7--host found at:192.168.111.20--time:888 <----- this host does not exist!!
8--host found at:192.168.111.20--time:852 <----- this host does not exist!!
4--host found at:192.168.111.20--time:997 <----- this host does not exist!!
1--host found at:192.168.111.20--time:1107 <----- this host does not exist!!
3--host found at:192.168.111.21--time:38
6--host found at:192.168.111.21--time:1
5--host found at:192.168.111.21--time:1
10--host found at:192.168.111.21--time:2
2--host found at:192.168.111.22--time:3 <----- this host does not exist!!
9--host found at:192.168.111.21--time:2
7--host found at:192.168.111.21--time:1
4--host found at:192.168.111.21--time:3
1--host found at:192.168.111.21--time:39
2--done.
1--host found at:192.168.111.22--time:5 <----- this host does not exist!!
1--done.
10--host found at:192.168.111.22--time:40 <----- this host does not exist!!
3--host found at:192.168.111.22--time:192 <----- this host does not exist!!
6--host found at:192.168.111.22--time:75 <----- this host does not exist!!
8--host found at:192.168.111.21--time:230
5--host found at:192.168.111.22--time:155 <----- this host does not exist!!
4--host found at:192.168.111.22--time:78 <----- this host does not exist!!
9--host found at:192.168.111.22--time:77 <----- this host does not exist!!
7--host found at:192.168.111.22--time:76 <----- this host does not exist!!
10--done.
6--done.
4--done.
5--done.
3--done.
7--done.
9--done.
8--no host at:192.168.111.22
8--done.
ALL DONE

I created this test (it's basically the same as your class):
import java.util.*;
import java.net.*;
public class IsReachableTest_2 implements Runnable {
    private final String[] addresses = new String[] {
         "www.sun.com",
         "129.42.16.99" // www.ibm.com which is not reachable
    public void run(){
        try {
            for (int i = 0; i < addresses.length; i++) {
                final long start = System.nanoTime();
                final String address = addresses;
     if (InetAddress.getByName(address).isReachable(5000)) {
     System.out.println(Thread.currentThread().getName() + ": Host found at: " + address +
          " --time: " + (System.nanoTime() - start) / 1000);
     } else System.out.println("no host at: " + address);
} catch(Exception e){
e.printStackTrace();
System.out.println("Thread " + Thread.currentThread().getName() + " DONE");
public static void main(String[] args) {
System.out.println(
     System.getProperty("java.vendor") +
     " " +
     System.getProperty("java.version") +
     " running on " +
     System.getProperty("os.name") +
     " " +
     System.getProperty("os.version")
for (int i = 0; i < 10; i++) {
     final Thread t = new Thread(new IsReachableTest_2(), "THREAD " + (i+1));
     t.start();
And I get:
Sun Microsystems Inc. 1.5.0-beta running on Windows 2000 5.0
THREAD 1: Host found at: www.sun.com --time: 217653
THREAD 3: Host found at: www.sun.com --time: 214404
THREAD 6: Host found at: www.sun.com --time: 214900
THREAD 4: Host found at: www.sun.com --time: 215901
THREAD 5: Host found at: www.sun.com --time: 216666
THREAD 10: Host found at: www.sun.com --time: 216620
THREAD 9: Host found at: www.sun.com --time: 217405
THREAD 2: Host found at: www.sun.com --time: 220705
THREAD 7: Host found at: www.sun.com --time: 220845
THREAD 8: Host found at: www.sun.com --time: 221384
no host at: 129.42.16.99
Thread THREAD 4 DONE
no host at: 129.42.16.99
Thread THREAD 6 DONE
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
Thread THREAD 5 DONE
Thread THREAD 10 DONE
Thread THREAD 9 DONE
Thread THREAD 7 DONE
Thread THREAD 3 DONE
Thread THREAD 1 DONE
Thread THREAD 2 DONE
Thread THREAD 8 DONE
HOWEVER: I was getting some strange results every so often. Results like:
Sun Microsystems Inc. 1.5.0-beta running on Windows 2000 5.0
THREAD 3: Host found at: www.sun.com --time: 261132
THREAD 9: Host found at: www.sun.com --time: 264183
THREAD 2: Host found at: www.sun.com --time: 266447
THREAD 6: Host found at: www.sun.com --time: 266596
THREAD 8: Host found at: www.sun.com --time: 267192
THREAD 5: Host found at: www.sun.com --time: 268610
THREAD 4: Host found at: www.sun.com --time: 269849
THREAD 1: Host found at: www.sun.com --time: 280978
THREAD 7: Host found at: www.sun.com --time: 272589
THREAD 10: Host found at: www.sun.com --time: 273162
THREAD 3: Host found at: 129.42.16.99 --time: 13657
Thread THREAD 3 DONE
THREAD 4: Host found at: 129.42.16.99 --time: 4123
THREAD 2: Host found at: 129.42.16.99 --time: 9439
THREAD 5: Host found at: 129.42.16.99 --time: 6681
THREAD 8: Host found at: 129.42.16.99 --time: 7655
THREAD 6: Host found at: 129.42.16.99 --time: 8627
THREAD 9: Host found at: 129.42.16.99 --time: 10586
Thread THREAD 4 DONE
Thread THREAD 2 DONE
Thread THREAD 5 DONE
Thread THREAD 8 DONE
Thread THREAD 6 DONE
Thread THREAD 9 DONE
no host at: 129.42.16.99
Thread THREAD 7 DONE
no host at: 129.42.16.99
no host at: 129.42.16.99
Thread THREAD 10 DONE
Thread THREAD 1 DONE
Usually the first run after I had compiled the class (!?) This isn't a thread safety problem.

A question about thread programming ...

Is it possible to modify the following program such that the output is
ABCABCABC ...
I tried yield, but not getting results on every run.
The program is:
public class Example1 {
public static void main(String[] args) {
MyThread t1 = new MyThread("A");
MyThread t2 = new MyThread("B");
MyThread t3 = new MyThread("C");
t1.start();
t2.start();
t3.start();
class MyThread extends Thread {
private String message = "Hallo!";
public MyThread() {}
public MyThread(String s) {message = s;}
public void run() {
for (int i = 1; i <= 5; i++) {
System.out.print(message);
}

Not really, no. It's possible (not using yield) to force threads to run in a particular order, but it's kind of missing the point of using threads in the first place!
Yield is there purely to allow other threads the opportunity to run. It makes no guarantee about which thread will run next.
If you really must, you need to use a wait() call to force the thread to block, notifyAll calls to resurrect them, and some commonly accessed resource that allows each thread in turn to determine IF it is its turn to run when it is awakened by the notifyAll call. That seems to be the closest to the spirit of what you're trying to do.
It's a lot of work for something that you can more simply achieve by having only one thread of execution in the first place!

A question about search help and input help,PLZ take a look at it.

hi everyone,
i want to know the difference between search hlep and inpu help
can anyone tell me about that?
thanks

HI
BOTH ARE SAME
you can define F4 help in 2 ways
in SE11 or in the report program
IN SE11
Attaching a search help to a table field
Choose the field name, click on search help tab and
provide the name of the search help.
A search help is attached to a field of a table or structure in the maintenance transaction for this table/structure, analogously to attaching to a table. You must assign the interface parameters of the search help to any fields of the table/structure. The search field must be assigned to an EXPORT parameter of the search help at this time.
Attach the search help to the table field
The search help ZSTRAVELAG_NAME is therefore directly attached to the field AGENCYNUM of table ZSTRAVELAG.
Attaching a search help to a data element
Provide the search help name and the parameter name
under the further characteristics tab of the data element.
If the input help of a field is defined by its data element, no further screen fields can be used in the input help.
Also note that the input F4 help would be available wherever the data element is used.
Attaching a search help to a screen element
A search help can be directly assigned to a screen field in two ways.
The name of the search help must be entered in the Screen Painter in the Attributes for the field in the field Search help.
The name of the search help can be defined for selection screens in ABAP reports in the PARAMETERS or SELECT-OPTIONS statement directly following the supplement MATCHCODE OBJECT.
However, input help is only available for this particular screen.
in REPORT PROGRAM
in this way we declare in report program
TYPES : BEGIN OF ST_OBJID_SH,
OTYPE TYPE HRP1000-OTYPE,
OBJID TYPE HRP1000-OBJID,
END OF ST_OBJID_SH.
DATA : IT_OBJID_SH TYPE STANDARD TABLE OF ST_OBJID_SH.
DATA : WA_OBJID_SH TYPE ST_OBJID_SH.
SELECTION-SCREEN BEGIN OF BLOCK B1 WITH FRAME TITLE TEXT-001.
*SELECT-OPTIONS : S_OTYPE FOR HRP1001-OTYPE NO INTERVALS .
SELECT-OPTIONS : S_OBJID FOR HRP1001-OBJID NO INTERVALS .
SELECT-OPTIONS : DATE FOR SY-DATUM NO-EXTENSION OBLIGATORY.
SELECTION-SCREEN END OF BLOCK B1.
AT SELECTION-SCREEN ON VALUE-REQUEST FOR S_OBJID-LOW.
IF S_OBJID IS NOT INITIAL.
SELECT OTYPE OBJID FROM HRP1000
INTO TABLE IT_OBJID_SH
WHERE OTYPE = 'D'.
IF SY-SUBRC EQ 0.
SEARCH HELP FOR QUALIFICATION.
CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'
EXPORTING
DDIC_STRUCTURE = ' '
RETFIELD = 'OBJID'
PVALKEY = ' '
DYNPPROG = SY-REPID
DYNPNR = SY-DYNNR
DYNPROFIELD = 'S_OBJID'
STEPL = 0
WINDOW_TITLE =
VALUE = ' '
VALUE_ORG = 'S'
MULTIPLE_CHOICE = ' '
DISPLAY = ' '
CALLBACK_PROGRAM = ' '
CALLBACK_FORM = ' '
MARK_TAB =
IMPORTING
USER_RESET =
TABLES
VALUE_TAB = IT_OBJID_SH
FIELD_TAB =
RETURN_TAB = RETURN_TAB
DYNPFLD_MAPPING =
EXCEPTIONS
PARAMETER_ERROR = 1
NO_VALUES_FOUND = 2
OTHERS = 3
IF SY-SUBRC <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
ENDIF.
Check this out
http://www.sap-img.com/abap/value-request-for-parameter.htm
******************************8
sample program
report zrich_0001 .
data: begin of ihelp occurs 0,
field type char10,
ftext type char50,
end of ihelp.
data: a_field(20) type c.
select-options s_field for a_field.
initialization.
ihelp-field = 'A'.
ihelp-ftext = 'Description A'.
append ihelp.
ihelp-field = 'B'.
ihelp-ftext = 'Description B'.
append ihelp.
ihelp-field = 'C'.
ihelp-ftext = 'Description C'.
append ihelp.
at selection-screen on value-request for s_field-low.
call function 'F4IF_INT_TABLE_VALUE_REQUEST'
exporting
retfield = 'FIELD'
dynprofield = 'S_FIELD'
dynpprog = sy-cprog
dynpnr = sy-dynnr
value_org = 'S'
tables
value_tab = ihelp.
start-of-selection.
one more program....
REPORT ZHELP .
TABLES : MARA.
SELECTION-SCREEN BEGIN OF BLOCK B1 WITH FRAME TITLE TEXT-001.
PARAMETERS : P_MATNR(10) TYPE C.
SELECTION-SCREEN END OF BLOCK B1.
DATA : BEGIN OF ITAB OCCURS 0,
MATNR TYPE MATNR,
END OF ITAB.
AT SELECTION-SCREEN ON VALUE-REQUEST FOR P_MATNR.
SELECT MATNR
FROM MARA
INTO TABLE ITAB
UP TO 10 ROWS.
CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'
EXPORTING
RETFIELD = 'MATERIAL NUMBER'
DYNPPROG = SY-REPID
DYNPNR = SY-DYNNR
DYNPROFIELD = 'P_MATNR'
VALUE_ORG = 'S'
TABLES
VALUE_TAB = ITAB
EXCEPTIONS
PARAMETER_ERROR = 1
NO_VALUES_FOUND = 2
OTHERS = 3.
Create it from SE11.
enter search help
and create elementary
enter description and below Table name
and the fields
see the doc
1) Elementary search helps describe a search path. The elementary search help must define where the data of the hit list should be read from (selection method), how the exchange of values between the screen template and selection method is implemented (interface of the search help) and how the online input help should be defined (online behavior of the search help).
2) Collective search helps combine several elementary search helps. A collective search help thus can offer several alternative search paths.
3)An elementary search help defines the standard flow of an input help.
4) A collective search help combines several elementary search helps. The user can thus choose one of several alternative search paths with a collective search help.
5)A collective search help comprises several elementary search helps. It combines all the search paths that are meaningful for a field.
6)Both elementary search helps and other search helps can be included in a collective search help. If other collective search helps are contained in a collective search help, they are expanded to the level of the elementary search helps when the input help is called.
http://help.sap.com/saphelp_nw04/helpdata/en/cf/21ee38446011d189700000e8322d00/content.htm
http://help.sap.com/saphelp_nw04/helpdata/en/cf/21ee45446011d189700000e8322d00/content.htm
pls go through this for search help creation
http://help.sap.com/saphelp_nw2004s/helpdata/en/41/f6b237fec48c67e10000009b38f8cf/content.htm

Question about Threads

Hi,
imagine that I have a class as below:
public class MyVector
private IntegerVector vect;
public Synchronized void write(){
vect.f();
public Synchronized void read(){
vect.g();
Where f and g are non Synchronized and non-static public methods of IntegerVector .
Imagine that two threads as below:
thread one :
class ThreadOne extends Thread
public ThreadOne(MyVector v)
this.v=v;
public void run()
v.write();
class ThreadTwo extends Thread
public ThreadTwo(MyVector v)
this.v=v;
public void run()
v.read();
My question is that if there will be any conflict between thread1 and thread2 for having the lock on
object MyVector v ?the methods read and write are Synchronized but they call non-Synchronized methods f() and g()
of field "IntegerVector vect" of "MyVector v "!
Thanks,
Behnaz

bandarurm wrote:
jverd wrote:
bandarurm wrote:
@OP - Also, remember that there are only two types of locks (aka monitors), which are Object level lock and Class level lock. No. All locks are identical.Could you explain this further? As I thought there is a class level lock (java.lang.Class) for a class with static synchronized methods. And, there is an object level lock, which is a built-in lock that every object has in java, by default.Whenever you synchronize a block of code or a method, you're just obtaining some object's lock. Synchronized methods are just shorthand for obtaining particular objects' locks.
Synchronization is always the same. Declaring a method synchronized is just shorthand for what you could do by explicitly syncing a block of code on a particular object.
class Foo {
synchronized void bar() {
    // body
// is the same as
void bar() {
    synchronized (this) {
      // body
// and
static synchronized qux() {
    // body
// is the same as
static qux() {
    synchronized (Foo.class) {
      // body
}In all cases, you're just syncing on an object, and which object doesn't matter, except to other methods or blocks that sync on the same object. Everything else is identical.
The fact that synchronized static methods obtain one particular lock and non-static ones obtain a different one is not indicative of different kinds of locks. It's always just some object's lock, and no lock behaves differently from any other.
Edited by: jverd on Apr 20, 2009 10:46 AM

Question about Threads/Servlets

Let's say I have a servlet that opens a socket connection to a server application. On the server end, I would have to make a thread for each connection. But what about the Servlet? do I have to deal with Threads on the servlet side or does the servlet engine takes care of that?

Unless your servlet implements the SingleThreadModel interface, the servlet container shoud take care of running each request to your servlet in a separate thread.
Andy Nguyen

About Threads help! help!

my lock can not work as my expecked,the key code segments as follows:
code segment1 and code segment2 belong to different threads, when the segment1 get the observer's lock the segment2 should stop because of lacking of resource. but the true testing result is
when ran into offset() ,the segment2 got resource ,and ran. the two segments has the same object ,but it can't synchronize ,i don't know why. help!help!
code segment 1:
synchronized (observer)
if (offset() == 0)
System.out.println("success！！！");
observer.cleanCounter();
//wait
try
observer.wait();
catch (InterruptedException ex1)
code segment 2:
synchronized(observer){
observer.increase() ;
System.out.println("increase!") ;
if(observer.isLimited()){
observer.notify() ;
System.out.println("notify!") ;

ok!
private int offset()
//System.out.println("enter offset!") ;
DB db = new DB();
String sql = "select log_id,softSN,SMS_content,audit_state"
+ " from SMS_content"
+ " where audit_state != 'n'";
ResultSet rs = null;
try
//System.out.println(sql) ;
rs = db.executeQuery(sql);
if (rs == null)
return -1;
while (rs.next())
String auditState = rs.getString("audit_state");
String softSN = rs.getString("softSN");
String smsContent = rs.getString("SMS_content");
String logId = rs.getString("log_id");
//未通过审核
if (auditState.equals("d"))
//插入审核失败表
System.out.println("enter deny!");
String sqlInsert =
"insert into audit_fail(softSN,log_id,SMS_content)"
+ "values('" + softSN + "'," + logId + ",'" + smsContent + "')";
if (db.executeUpdate(sqlInsert) != 1)
return -1;
// System.out.println("success!") ;
//从SMS_content,SMS_cache表中删除数据
String sqlDel = "delete from SMS_content where log_id=" +
logId;
if (db.executeUpdate(sqlDel) != 1)
return -1;
sqlDel = "delete from SMS_cache where log_id=" +
logId;
if (db.executeUpdate(sqlDel) != 1)
return -1;
// System.out.println("sucsess2!") ;
//审核通过
else
// System.out.println("inter permit!") ;
Queue queue = new Queue();
//System.out.println(queue.i + " i指为");
//System.out.println(Integer.parseInt(logId) + " logId");
ResultSet rsSMSContent = queue.getSMSContent(Integer.parseInt(logId));
// System.out.println(rsSMSContent + " dddddddddddd");
Enterprise enterprise = new Enterprise();
int enterID = enterprise.getEnterID(softSN);
// System.out.println(enterID + " aaaaaaaaa");
PropertiesFile file = QueueCount.getInstance();
// System.out.print(file + " bbbbbbbb");
int defaultPriority = enterprise.getEnterDefaultPriority(softSN);
//System.out.println(defaultPriority + " cccccccccc");
int createResult = -1;
if (defaultPriority != 3)
createResult = queue.createQueue(rsSMSContent,
Integer.parseInt(logId), enterID,
file, defaultPriority);
// System.out.println("createResult"+createResult) ;
// System.out.println("into queue") ;
else
createResult = queue.createQueue(rsSMSContent,
Integer.parseInt(logId), enterID,
file, 2);
//System.out.println("createResult"+createResult) ;
// System.out.println("into queue") ;
rsSMSContent.close();
queue.close();
if (createResult == 0)
String sqlDel = "delete from SMS_content where log_id=" + logId;
// System.out.println("sql1") ;
if (db.executeUpdate(sqlDel) != 1)
return -1;
sqlDel = "delete from SMS_cache where log_id=" + logId;
if (! (db.executeUpdate(sqlDel) >= 1))
return -1;
// System.out.println("sql2") ;
return 0;
catch (Exception e)
e.printStackTrace();
return -1;
finally
try
if (rs != null)
rs.close();
db.close();
catch (SQLException ex)

A question about thread!(help a chinese learner)

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