1. Thread Lifecycle and Thread Methods
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2. Objective
On completion of this period, you would be
able to learn
• Thread Lifecycle
• Thread methods
• Example Programs
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3. Recap
• In the previous class we have seen how to set the
priorities of threads
• Thread class provides 3 constants for setting
priorities
• Thread.NORM_PRIORITY
• Thread.MAX_PRIORITY
• Thread.MIN_PRIORITY
• Thread class also provides two methods
• setPriority()
• getPriority()
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4. Thread Life Cycle
• Just like a Process has life cycle
• Thread also has a life cycle
• A Thread under goes different states while it is
executing
• We know the process state diagram
• It is used to represent the life cycle of a process
• Similarly the life cycle of a thread can be represented by
thread state diagram
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5. Thread Life Cycle
Contd . . .
• A Thread can be in one of the following states
• New born
• Running
• Ready to run
• Blocked
• Dead
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6. Thread Life Cycle
Contd . . .
The following figure shows the life cycle of a thread
New born
New born
start() stop()
stop()
Ready to
Running Dead
Dead
Run
yield()
suspend() resume()
wait() notifyAll() stop()
sleep() notify()
Blocked
Blocked
Fig. 36.1. Thread lifecycle – state transition diagram
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7. Thread Life Cycle
Contd . . .
• When a thread object is created, it enters new born state
• start() method changes the state to either running or
ready to state
• suspend(), sleep()or wait() methods moves the thread to
a blocked state
• resume(), notify() or notifyAll() methods moves the
blocked thread to running/ready to run state
• A call to stop() method kills the thread
• A running thread can give away the control of execution
to another thread by calling yield() methods
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8. Methods of Thread
•Some of the methods of the Thread class are
• start()
• stop()
• suspend()
• resume()
• wait()
• notify()
• notifyAll()
• isAlive()
• yield()
• join()
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9. isAlive() method
• The signature of this method
public final boolean isAlive()
• Returns true if the thread is not dead (run has not
completed)
• Returns false if the thread is dead
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10. join() method
• The signature of join() method
public final void join();
public final void join(long t);
• Calling thread waits for thread receiving message to die
before it can proceed
• No argument or 0 millisecond argument means thread
will wait indefinitely
• Can lead to deadlock/indefinite postponement
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11. Example Program
class NewThread implements Runnable {
String name; // name of thread
Thread t;
NewThread(String threadname) {
name = threadname;
t = new Thread(this, name);
System.out.println("New thread: " + t);
t.start(); // Start the thread
}
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12. Example Program
Contd . . .
public void run() {
try {
for(int i = 5; i > 0; i--) {
System.out.println(name + ": " + i);
Thread.sleep(1000);
}
} catch (InterruptedException e) {
System.out.println(name + "
interrupted.");
}
System.out.println(name + " exiting.");
}
}
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13. Example Program
Contd . . .
class DemoJoin {
public static void main(String args[]) {
NewThread ob1 = new NewThread("One");
NewThread ob2 = new NewThread("Two");
NewThread ob3 = new NewThread("Three");
System.out.println("Thread One is alive: “ +
ob1.t.isAlive());
System.out.println("Thread Two is alive: “ +
ob2.t.isAlive());
System.out.println("Thread Three is alive: “ +
ob3.t.isAlive()); Use of isAlive()
At this moment all threads
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are alive and return true

14. Example Program
Contd . . .
try {
System.out.println("Waiting for threads to finish."); main() thread waits
ob1.t.join(); until all threads finish
their work
ob2.t.join();
ob3.t.join(); As threads have
} catch (InterruptedException e) { finished,
isAlive() returns false
System.out.println("Main thread Interrupted");
}
System.out.println("Thread One is alive: “ + ob1.t.isAlive());
System.out.println("Thread Two is alive: “ + ob2.t.isAlive());
System.out.println("Thread Three is alive: “ + ob3.t.isAlive());
System.out.println("Main thread exiting.");
}
} 14

15. Example Program
Contd . . .
Output
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16. suspend() method
• The signature of this method
public final void suspend();
• If the thread is alive, it is suspended and makes no
further progress unless and until it is resumed
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17. resume() method
• The signature of this method
public final void resume();
• If the thread is alive but suspended, it is resumed
and is permitted to make progress in its execution.
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18. Example Program
class NewThread implements Runnable {
string name; // name of thread
Thread t;
NewThread(String threadname) {
name = threadname;
t = new Thread(this, name);
System.out.println("New thread: " + t);
t.start(); // Start the thread
}
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19. Example Program
Contd . . .
public void run() {
try {
for(int i = 10; i > 0; i--) {
System.out.println(name + ": " + i);
Thread.sleep(200);
}
} catch (InterruptedException e) {
System.out.println(name + " interrupted.");
}
System.out.println(name + " exiting.");
}
} 19

20. Example Program
Contd . . .
class SuspendResume {
public static void main(String args[]) {
NewThread ob1 = new NewThread("One");
NewThread ob2 = new NewThread("Two");
try {
Thread.sleep(1000);
ob1.t.suspend();
System.out.println("Suspending thread One");
Thread.sleep(1000);
ob1.t.resume();
System.out.println("Resuming thread One");
ob2.t.suspend();
System.out.println("Suspending thread Two");
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21. Example Program
Contd . . .
Thread.sleep(1000);
ob2.t.resume();
System.out.println("Resuming thread Two");
} catch (InterruptedException e) {
System.out.println("Main thread Interrupted");
}
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22. Example Program
Contd . . .
// wait for threads to finish
try {
System.out.println("Waiting for threads to
finish.");
ob1.t.join();
ob2.t.join();
} catch (InterruptedException e) {
System.out.println("Main thread Interrupted");
}
System.out.println("Main thread exiting.");
}
} 22

23. Example Program
Output
Contd . . .
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24. Summary
• In this class we have discussed
• The life cycle of thread
• The state transition diagram
• The thread methods
• isAlive()
• join()
• suspend()
• resume()
• In the next lesson we look at the concept of
synchronization
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25. Quiz
1. A suspended thread goes to ready state by
calling
A. start() method
B. ready() method
C. resume() method
D. None
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26. Quiz Contd..
2. Which of the following method changes the
state of the thread to blocked state ?
A. stop()
B. suspend()
C. notify()
D. notify All()
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27. Quiz Contd..
3. What is the return type of isAlive() method ?
A. int
B. float
C. double
D. boolean
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28. Quiz Contd..
4. Which of the following method kills the
thread ?
A. kill()
B. stop()
C. end()
D. None
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29. Frequently Asked Questions
1. Draw and explain the state-transition diagram of
thread
2. What are the different states the thread enters
while it is executing ?
3. Write the syntax of using isAlive(), join()
methods
4. Write the syntax of using suspend(), resume()
methods
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