IllegalThreadStateException

[Swati Kadam]

class Mits implements Runnable {

public static void main ( String args [ ] ) {
Thread tx = new Thread ( new Mits ( ) , " Krux " ) ;
tx . start ( ) ;
System . out . println ( " Terminated " ) ;
}

public void run ( ) {
try
{
Thread . currentThread ( ) . setDaemon ( true ) ;
Thread . sleep ( 10000 ) ;
}
catch (InterruptedException e) { }
}
};
The output is:

Terminated
Exception in thread " Krux " java.lang.IllegalThreadStateException
at java.lang.Thread.setDaemon(Unknown Source)
at Mits.run(Mits.java:12)
at java.lang.Thread.run(Unknown Source)

Why this exception comes???

[Tim Weide]

setDaemon() throws IllegalThreadStateException if the thread is active.

[Swati Kadam]

Originally posted by Tim Weide:
setDaemon() throws IllegalThreadStateException if the thread is active.

So can we call setdeamon() after start() method???

[Henry Wong]

Originally posted by Swati Kadam:
So can we call setdeamon() after start() method???

Here is the relevant excerpt from the JavaDoc....

This method must be called before the thread is started.

Henry

[Deepak Chopra]

Hi Swati,

You are making the thread a Daemon thread, Just want to ask you one thing:

Once a thread started, Can you change it properties ? Like its name or something else..!!

I know most probably your answer will be "NO". Similarly setDaemon cause your thread to run as a Daemon thread in the background. So you must set the Daemon property of thread before running. By default it start running like a non-Daemon, now in between its running state we can not make it Daemon.

It will be either fully Daemon or non-Daemon.