But for better understanding the threads, we are explaining it in the 5 states.

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Ashlee Houston
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Life cycle f a Thread (Thread States) A thread can be in ne f the five states. Accrding t sun, there is nly 4 states in thread life cycle in java new, runnable, nn-runnable and terminated.

1 Life cycle f a Thread (Thread States) A thread can be in ne f the five states. Accrding t sun, there is nly 4 states in thread life cycle in java new, runnable, nn-runnable and terminated. There is n running state. But fr better understanding the threads, we are explaining it in the 5 states. The life cycle f the thread in java is cntrlled by JVM. The java thread states are as fllws: 1. New 2. Runnable 3. Running 4. Nn-Runnable (Blcked) 5. Terminated

2 1) New The thread is in new state if yu create an instance f Thread class but befre the invcatin f start() methd. When we create a new Thread bject using new peratr, thread state is New Thread. At this pint, thread is nt alive and it s a state internal t Java prgramming. 2) Runnable The thread is in runnable state after invcatin f start() methd, but the thread scheduler has nt selected it t be the running thread. When we call start() functin n Thread bject, it s state is changed t Runnable. The cntrl is given t Thread scheduler t finish it s executin. Whether t run this thread instantly r keep it in runnable thread pl befre running, depends n the OS implementatin f thread scheduler. 3) Running The thread is in running state if the thread scheduler has selected it. When thread is executing, it s state is changed t Running. Thread scheduler picks ne f the thread frm the runnable thread pl and change it s state t Running. Then CPU starts executing this thread. A thread can change state t Runnable, Dead r Blcked frm running state depends n time slicing, thread cmpletin f run() methd r waiting fr sme resurces. 4) Nn-Runnable (Blcked) This is the state when the thread is still alive, but is currently nt eligible t run. A thread can be waiting fr ther thread t finish using thread jin r it can be waiting fr sme resurces t available. Fr example prducer cnsumer prblem r waiter ntifier implementatin r IO resurces, then it s state is changed t Waiting. Once the thread wait state is ver, it s state is changed t Runnable and it s mved back t runnable thread pl.

3 5) Terminated A thread is in terminated r dead state when its run() methd exits. Once the thread finished executing, it s state is changed t Dead and it s cnsidered t be nt alive. Java Thread Benefits 1. Java Threads are lightweight cmpared t prcesses; it takes less time and resurce t create a thread. 2. Threads share their parent prcess data and cde 3. Cntext switching between threads is usually less expensive than between prcesses. 4. Thread intercmmunicatin is relatively easy than prcess cmmunicatin. Hw t create thread There are tw ways t create a thread: 1. By extending Thread class 2. By implementing Runnable interface. Thread class: Thread class prvide cnstructrs and methds t create and perfrm peratins n a thread. Thread class extends Object class and implements Runnable interface. Cmmnly used Cnstructrs f Thread class: Thread() Thread(String name) Thread(Runnable r) Thread(Runnable r,string name)

4 Cmmnly used methds f Thread class: 1. public vid run(): is used t perfrm actin fr a thread. 2. public vid start(): starts the executin f the thread.jvm calls the run() methd n the thread. 3. public vid sleep(lng milisecnds): Causes the currently executing thread t sleep (temprarily cease executin) fr the specified number f millisecnds. 4. public vid jin(): waits fr a thread t die. 5. public vid jin(lng milisecnds): waits fr a thread t die fr the specified milisecnds. 6. public int getpririty(): returns the pririty f the thread. 7. public int setpririty(int pririty): changes the pririty f the thread. 8. public String getname(): returns the name f the thread. 9. public vid setname(string name): changes the name f the thread. 10. public Thread currentthread(): returns the reference f currently executing thread. 11. public int getid(): returns the id f the thread. 12. public Thread.State getstate(): returns the state f the thread. 13. public blean isalive(): tests if the thread is alive. 14. public vid yield(): causes the currently executing thread bject t temprarily pause and allw ther threads t execute. 15. public vid suspend(): is used t suspend the thread(depricated). 16. public vid resume(): is used t resume the suspended thread(depricated). 17. public vid stp(): is used t stp the thread(depricated). 18. public blean isdaemn(): tests if the thread is a daemn thread. 19. public vid setdaemn(blean b): marks the thread as daemn r user thread. 20. public vid interrupt(): interrupts the thread. 21. public blean isinterrupted(): tests if the thread has been interrupted. 22. public static blean interrupted(): tests if the current thread has been interrupted.

5 Runnable interface: The Runnable interface shuld be implemented by any class whse instances are intended t be executed by a thread. Runnable interface have nly ne methd named run(). 1. public vid run(): is used t perfrm actin fr a thread. Starting a thread: start() methd f Thread class is used t start a newly created thread. It perfrms fllwing tasks: A new thread starts(with new callstack). The thread mves frm New state t the Runnable state. When the thread gets a chance t execute, its target run() methd will run. 1) Java Thread Example by extending Thread class class Multi extends Thread{ public vid run(){ System.ut.println("thread is running..."); public static vid main(string args[]){ Multi t1=new Multi(); t1.start(); Output:thread is running...

6 2) Java Thread Example by implementing Runnable interface class Multi3 implements Runnable{ public vid run(){ System.ut.println("thread is running..."); public static vid main(string args[]){ Multi3 m1=new Multi3(); Thread t1 =new Thread(m1); t1.start(); Output: thread is running... If yu are nt extending the Thread class, yur class bject wuld nt be treated as a thread bject. S yu need t explicitely create Thread class bject. We are passing the bject f yur class that implements Runnable s that yur class run() methd may execute.

CSE 3320 Operating Systems Synchronization Jia Rao

CSE 3320 Operating Systems Synchrnizatin Jia Ra Department f Cmputer Science and Engineering http://ranger.uta.edu/~jra Recap f the Last Class Multiprcessr scheduling Tw implementatins f the ready queue