— Scott McNealy, Sun Microsystems Chairman, President and ceo

main()
myThread.start()
1
1
2
2
new thread
brainbarbell
Brain Barbell
What do you think the output will be if you run the 
ThreadTester class? (we’ll find out in a few pages)
Runnable 
interface

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networking 
and
threads
you are here
4
495
The three states of a new thread
A Thread instance has been 
created but not started. 
In other words, there is a 
Thread 
object, but no thread 
of execution.
NEW
RUNNABLE
T
hread t = new Thread(r);
When you start the thread, it 
moves into the runnable state. 
This means the thread is ready 
to run and just waiting for its 
Big Chance to be selected for 
execution. At this point, there is 
a new call stack for this thread.
t.start();
RUNNING
t.start();
Selected to run
This is the state all threads lust 
after! To be The Chosen One. 
The Currently Running Thread. 
Only the JVM thread scheduler 
can make that decision. You 
can sometimes 
influence that 
decision, but you cannot force a 
thread to move from runnable 
to running. In the running 
state, a thread (and ONLY this 
thread) has an active call stack, 
and the method on the top of 
the stack is executing.
Thread t = new Thread(r);
this is where a thread 
wants to be! 
But there’s more. Once the thread becomes 
runnable, it can move back and forth between 
runnable, running, and an additional state: 
temporarily not runnable (also known as ‘blocked’).
“I’m good to go!”
“Can I 
supersize 
that for 
you?”
“I’m waiting to 
get started.”

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