The document discusses thread lifecycle and methods in Java. It explains that a thread goes through different states like new, ready, running, blocked, and dead. It provides a state transition diagram and describes each state. It also discusses various thread methods like start(), stop(), suspend(), resume(), wait(), notify(), isAlive(), and join(). Example programs are provided to demonstrate using these methods and the thread lifecycle.

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
2

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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