Some method still running when my program should be finished... how do I find out?

[blazedaces]

My program is still running when I am finished. I outputted text at the end of the main, so I know it gets there just fine and the program finished everything just fine... but the jvm is still running. How do I find out where it's still running so I can at least know specifically what's the problem? Any special programs or ideas?

Thanks,

-blazed

[JosAH]

You must have started threads then somewhere in your program. Make those
threads 'daemon threads' (check the API documentation) before you start them.
Daemon threads die when the main thread dies so the JVM will stop (it has
nothing more to do).

kind regards,

Jos

[blazedaces]

You must have started threads then somewhere in your program. Make those
threads 'daemon threads' (check the API documentation) before you start them.
Daemon threads die when the main thread dies so the JVM will stop (it has
nothing more to do).

kind regards,

Jos

I'm sorry, but unfortunately I have 0 experience with threads. I looked into daemon threads, but honestly, I'm not starting a new thread anywhere in the program. I also checked and closed all streams, I don't know what this could be, really.

I did find this in the class thread API:

"When a Java Virtual Machine starts up, there is usually a single non-daemon thread (which typically calls the method named main of some designated class)."

I could try to call this class from another program (which I'm planning on doing anyway) instead of using its own main... but I wonder if something will continue to run in the background.

I know of threads, and a fairly good idea of what they are and how they work. I'm wondering if whatever methods I'm calling create threads (SAX ? ). I've been using sax for a while though and never had this problem before...

Thanks for all your help,

-blazed

[r035198x]

I'm sorry, but unfortunately I have 0 experience with threads. I looked into daemon threads, but honestly, I'm not starting a new thread anywhere in the program. I also checked and closed all streams, I don't know what this could be, really.

I did find this in the class thread API:

"When a Java Virtual Machine starts up, there is usually a single non-daemon thread (which typically calls the method named main of some designated class)."

I could try to call this class from another program (which I'm planning on doing anyway) instead of using its own main... but I wonder if something will continue to run in the background.

I know of threads, and a fairly good idea of what they are and how they work. I'm wondering if whatever methods I'm calling create threads (SAX ? ). I've been using sax for a while though and never had this problem before...

Thanks for all your help,

-blazed

May I know
1.) What your program does
2.) How you determined that the JVM is still running after your program has exited

[blazedaces]

May I know
1.) What your program does
2.) How you determined that the JVM is still running after your program has exited

Sure thing:

1) My program parses an xml file and writes to another file all the "tags" in the xml file. Tags are basically locations in which characters/data are read... It also records specific pieces of data that I will need. I haven't written it yet, but afterwards, I will read the file again after the user chooses what "tags" or data they are interested in, and then store the data into a predetermined format of bytecode.

To keep things simple, it parses the xml file and writes certain things to a file that it read. That's about it. To be even more specific, for a file that looks like this:

<?xml version="1.0"?>
 
<poem xmlns="http://www.megginson.com/ns/exp/poetry">
    <title>Roses are Red</title>
    <l>  Roses are red,</l>
    <l>Violets are blue;</l>
    <l>Sugar is sweet,</l>
    <l>And I love you.</l>
</poem>
 

the outputted text looks look like this:

    * setDocumentLocator() called
Parsing begins...
Mapping starts for prefix  mapped to URI http://www.megginson.com/ns/exp/poetry
Mapping ends for prefix 
...Parsing ends.
 
Start gps-time(s): 0.0
End gps-time(s): 0.0
Total time(s): 0.0
Tags:
 
poem\title\
poem\l\
 

I actually ran the program on that file and spit out that text file.

The tags are "poem\title\" and "poem\l\".

2) I'm using JCreator and if you look on the top part there's an execute button and next to it or after a few more buttons there is a "stop" or kill button. You can't hit the execute button while it's still running and you can't hit the kill button unless something is running. When the program is finished the execute button is disabled and the kill button is able to be clicked. Unless I hit the kill button or put system.exit(number) at the end of my main it won't stop.

Here's my main just in case it'll help:

public static void main(String args[]) {
 
        OutputTagsXMLReader XMLReader = new OutputTagsXMLReader();
 
        XMLReader.parseFile();
        //I tried putting a system.out.println("text") here and printed the "text" to the screen, meaning it must be finishing the .parseFile() method and all methods along the way, right?
    }
 

Since I don't visibly start threads along the way I'm lead to believe something else in the parser perhaps is starting a thread, but I've never ran into this problem before and have been reading these xml files for quite a bit of time now since I started working here.

Hope that answers your questions and thanks for your help,

-blazed

[r035198x]

Sure thing:

1) My program parses an xml file and writes to another file all the "tags" in the xml file. Tags are basically locations in which characters/data are read... It also records specific pieces of data that I will need. I haven't written it yet, but afterwards, I will read the file again after the user chooses what "tags" or data they are interested in, and then store the data into a predetermined format of bytecode.

To keep things simple, it parses the xml file and writes certain things to a file that it read. That's about it. To be even more specific, for a file that looks like this:

<?xml version="1.0"?>
 
<poem xmlns="http://www.megginson.com/ns/exp/poetry">
    <title>Roses are Red</title>
    <l>  Roses are red,</l>
    <l>Violets are blue;</l>
    <l>Sugar is sweet,</l>
    <l>And I love you.</l>
</poem>
 

the outputted text looks look like this:

    * setDocumentLocator() called
Parsing begins...
Mapping starts for prefix  mapped to URI http://www.megginson.com/ns/exp/poetry
Mapping ends for prefix 
...Parsing ends.
 
Start gps-time(s): 0.0
End gps-time(s): 0.0
Total time(s): 0.0
Tags:
 
poem\title\
poem\l\
 

I actually ran the program on that file and spit out that text file.

The tags are "poem\title\" and "poem\l\".

2) I'm using JCreator and if you look on the top part there's an execute button and next to it or after a few more buttons there is a "stop" or kill button. You can't hit the execute button while it's still running and you can't hit the kill button unless something is running. When the program is finished the execute button is disabled and the kill button is able to be clicked. Unless I hit the kill button or put system.exit(number) at the end of my main it won't stop.

Here's my main just in case it'll help:

public static void main(String args[]) {
 
        OutputTagsXMLReader XMLReader = new OutputTagsXMLReader();
 
        XMLReader.parseFile();
        //I tried putting a system.out.println("text") here and printed the "text" to the screen, meaning it must be finishing the .parseFile() method and all methods along the way, right?
    }
 

Since I don't visibly start threads along the way I'm lead to believe something else in the parser perhaps is starting a thread, but I've never ran into this problem before and have been reading these xml files for quite a bit of time now since I started working here.

Hope that answers your questions and thanks for your help,

-blazed

Does it not open a console window written "press any key to continue" after execution?

[blazedaces]

Does it not open a console window written "press any key to continue" after execution?

No.

But what do you mean? Should it? Why? Do netbeans and other IDE's do that? Or are you saying my program should do that?

-blazed

[r035198x]

No.

But what do you mean? Should it? Why? Do netbeans and other IDE's do that? Or are you saying my program should do that?

-blazed

No, different IDE's show the output on different windows. I thought you had said something about a message being printed to the screen.
I remember now that JCreator shows a console window somewhere at the bottom. What is the message printed there?
I don't like having to ask for the code ...

[JosAH]

Just another question: do you do *anything* with AWT or Swing in your program?

kind regards,

Jos

[blazedaces]

No, different IDE's show the output on different windows. I thought you had said something about a message being printed to the screen.
I remember now that JCreator shows a console window somewhere at the bottom. What is the message printed there?
I don't like having to ask for the code ...

The message simply says this:

--------------------Configuration: <Default>--------------------
Finished Writing Tag Log File

Sorry, I took out that message that I said I was writing. I just wrote it to the screen at one point to verify that the program got to that stage. If I'm misunderstanding what you mean could you specify what message of mine you're referring to?

Listen, if this was shorter I would post all my code, but it's a little too much to put all on the forum. The reader class isn't that big and this is it:

/**
 * @(#)PrettyPrintXMLReader.java
 *
 *
 * @author 
 * @version 1.00 2007/5/14
 */
 
import java.util.*;
import java.io.*;
import org.xml.sax.*;
import org.xml.sax.helpers.XMLReaderFactory;
import java.awt.*;
import AsafUtil.OnlyExt;
 
public class OutputTagsXMLReader {
    private String fileName = "";
 
    public String fileName() { return this.fileName; }
 
    private FilenameFilter filter = new OnlyExt("xml");
 
    FileReader FID;
 
    // Initiate handler
    public OutputTagsHandler handler;
 
    public OutputTagsXMLReader() {
        FileDialog fd = new FileDialog(new Frame(), "Choose a .out file to open...", FileDialog.LOAD);
        fd.setFilenameFilter(filter);
        fd.setFile("*.xml"); 
        fd.setLocation(50, 50);
        fd.setVisible(true);
 
        fileName = fd.getDirectory() + System.getProperty("file.separator") + fd.getFile();
 
        handler = new OutputTagsHandler(fd.getFile());
    }
 
    public static void main(String args[]) {
 
        OutputTagsXMLReader XMLReader = new OutputTagsXMLReader();
 
        XMLReader.parseFile();
    }
 
    // parseFile chooses the filename and then reads the file and sends it
    // to parseFile(FID)
    public void parseFile() {
        FID=null;
        try {
            if (!fileName.equals(""))
                FID = new FileReader(fileName);
            else {
                System.out.println("Filename not inputted, can't parse... exiting");
                try {
                    FID.close();
                } catch (IOException e) {
                    System.out.println("Error trying to close FID:\n");
                    e.printStackTrace();
                    System.out.println();
                }
                System.exit(0);
            }
            parseFile(FID);
        }
        catch (FileNotFoundException e) {
            System.out.println("File not found exception: ");
            e.printStackTrace();
        } finally {
            try {
                FID.close();
            } catch (IOException e) {
                System.out.println("Error trying to close FID:\n");
                e.printStackTrace();
                System.out.println();
            }
        }
    }
 
    // This method initiates the XMLReader, sets the handlers, and finally,
    // parses the file.
    //
    // @param = "FID" - FileReader of a prechosen filename that is to be parsed
    public void parseFile(FileReader FR) {
        try {
            // Create the XML reader;
            XMLReader reader = null;
            try {
                reader = XMLReaderFactory.createXMLReader();
            } catch (SAXException e) {
                System.out.println("Failed to create XMLReader:\n"); 
                e.printStackTrace();
                System.exit(1);
            }
 
            // Assign the handlers    
            reader.setContentHandler(handler);
            reader.setErrorHandler(handler);
 
            // Parse the document
            InputSource systemId = new InputSource(FR);
            try {
                reader.parse(systemId);
            } catch (SAXException e1) {
                System.out.println(systemId +
                           " failed with XML error:\n");
                           e1.printStackTrace();
            } catch (IOException e2) {
                System.out.println(systemId +
                           " failed with I/O error:\n");
                           e2.printStackTrace();
            }
            System.out.print("\n");
        } finally {
            try {
                FR.close();
            } catch (java.io.IOException e) {
                System.out.println("Unable to close FR, must exit...");
                e.printStackTrace();
                System.exit(1);
            }
        }
    }
}

Thanks for all your help and sorry for the misunderstanding,

-blazed

[JosAH]

Got it. As I suspected (see my previous reply) you are using the AWT event
dispatcher thread (you're using a FileDialog). That thread isn't a daemon thread
so it keeps on running after the main thread died. Terminate your program with
a System.exit(<some number>) and all will be fine again.

kind regards,

Jos

[r035198x]

Most probably the parsing is not completing then.The parse method is synchronous. see the specs for it.

[r035198x]

Got it. As I suspected (see my previous reply) you are using the AWT event
dispatcher thread (you're using a FileDialog). That thread isn't a daemon thread
so it keeps on running after the main thread died. Terminate your program with
a System.exit(<some number>) and all will be fine again.

kind regards,

Jos

Oh, I missed that thread.

[blazedaces]

Got it. As I suspected (see my previous reply) you are using the AWT event
dispatcher thread (you're using a FileDialog). That thread isn't a daemon thread
so it keeps on running after the main thread died. Terminate your program with
a System.exit(<some number>) and all will be fine again.

kind regards,

Jos

Well, here's the thing. I want to call this class, run it, then continue running a program which will read that file, and reparse for specific data to turn it into bytecode. If I system.exit(0) won't it stop everything? I know I could just let that old file dialog run in the background, but it seems like a waste of processor? Is there a way to specifically stop this class/program from running and continue the rest?

... Am I going to have to run it as a thread and kill it when it's finished or something like that?

-blazed

[JosAH]

Well, here's the thing. I want to call this class, run it, then continue running a program which will read that file, and reparse for specific data to turn it into bytecode. If I system.exit(0) won't it stop everything? I know I could just let that old file dialog run in the background, but it seems like a waste of processor? Is there a way to specifically stop this class/program from running and continue the rest?

... Am I going to have to run it as a thread and kill it when it's finished or something like that?

-blazed

Yep, if you System.exit(<number>) everything dies. About that AWT thread:
the thread doesn't do anything at all (read: doesn't take up cpu time) when there
are no user instigated events and nothing needs to be repainted, so you can let
it run forever. It won't stop running when your main thread dies though, hence the
System.exit(<number>).

You won't lose performance because of that (waiting) thread. It was a design
issue for the designers of AWT/Swing: either have a multi threaded GUI thing,
which is a total mess (google for that) or have a single threaded, non daemon
thread take care of it all. You don't even want to terminate that thread when your
main thread terminates, i.e. it would be nearly impossible to build GUI applications
if that were the case.

Simply let that thread wait and invoke System.exit(<number>) when your main
thread dies. If you're really paranoia about it: check the ThreadGroup an use the
(deprecated) stop() method on the AWT thread.

kind regards,

Jos

[blazedaces]

Yep, if you System.exit(<number>) everything dies. About that AWT thread:
the thread doesn't do anything at all (read: doesn't take up cpu time) when there
are no user instigated events and nothing needs to be repainted, so you can let
it run forever. It won't stop running when your main thread dies though, hence the
System.exit(<number>).

You won't lose performance because of that (waiting) thread. It was a design
issue for the designers of AWT/Swing: either have a multi threaded GUI thing,
which is a total mess (google for that) or have a single threaded, non daemon
thread take care of it all. You don't even want to terminate that thread when your
main thread terminates, i.e. it would be nearly impossible to build GUI applications
if that were the case.

Simply let that thread wait and invoke System.exit(<number>) when your main
thread dies. If you're really paranoia about it: check the ThreadGroup an use the
(deprecated) stop() method on the AWT thread.

kind regards,

Jos

Thanks a lot. I guess I'll just use the system.exit(<number>) whenever I'm completely finished...

-blazed

[JosAH]

Thanks a lot. I guess I'll just use the system.exit(<number>) whenever I'm completely finished...

-blazed

Yup, that's the way to go or otherwise don't start up that AWT thread at all,
i.e. don't instantiate any AWT/Swing component at all. That 'setVisible()' method
is the culprit: it enqueues a repaint operation which is the job of that AWT thread.

kind regards,

Jos

[blazedaces]

Yup, that's the way to go or otherwise don't start up that AWT thread at all,
i.e. don't instantiate any AWT/Swing component at all. That 'setVisible()' method
is the culprit: it enqueues a repaint operation which is the job of that AWT thread.

kind regards,

Jos

What better way is there to ask the user what file to read or save to? Is there a way to make the file dialog appear without using setVisible? How can the AWT thread do it on it's own?

-blazed

[JosAH]

What better way is there to ask the user what file to read or save to? Is there a way to make the file dialog appear without using setVisible? How can the AWT thread do it on it's own?

-blazed

Nothing 'appears' out of itself without making it visible first. Either bail out if the
user didn't supply the correct command line argument(s) or use a shell or command
line interface for the correct arguments or go for the whole nine yards and
supply a gui (in which case you have to System.exit()).

kind regards,

Jos