Multitasking:-

  • Multiple tasks are performed at a time is called as multitasking.
  • We can perform a multiple tasks with the help of thread or a process.

Multithreading:-

  • It is a type of multitasking in which multiple tasks are performed with the help of thread.

Multiprocessing:-

  • Multiprocessing is a type of multitasking in which multiple tasks are performed with the help of multiple processes.

Multiple Programming:-

  • If the multiple tasks are performed on a multiple processor then it is called as multiple programming.

Multicore Programming:-

  • If the multiple tasks are performed with the help of different parts of same processor (core) then it is called as multiple Programming.

Multiuser:-

  • If multiuser shares a copy of an operating system then it is called as a multiuser operating system.

Thread Synchronization:-

e.g.

public class demo

{

private int balance;

public synchronized debit(int amt)

{

while(bal_amt<0)

wait();

bal = amt;

}

public synchronized credit(int amt)

{

bal = bal-amt;

notify();

}

}

Thread class constructors:-

  • Thread();
  • Thread(String tname);
  • Thread(Runnable object);
  • Thread(Runnable object, String s);
  • Thread(ThreadGroup t, String s);
  • Thread(ThreadGroup t, Runnable object);
  • Thread(ThreadGroup t, Runnable object, String s);

Inter thread communication:-

e.g.

class demo extends Thread

{

String str;

public demo(String s)

{

str = s;

}

public void run()

{

try{

for(;;)

{

System.out.println(str);

sleep(1000);

}

}

catch(InterruptException e)

{

System.out.println(e);

}

}

public ststic void main(String args[])

{

Thread t1 = new Thraed(first);

t1.start();

Thread t2 = new Thread(second);

t2.start();

}

}

class hello implements Runnable

{

String str;

public hello(String s)

{

str = s;

}

public void run()

{

try{

for(;;)

{

System.out.println(str);

sleep(1000);

}

}

catch(Exception e){…}

}

}

Multi Threading & Event Handelling

Multithreading:

  • Thread means single block or a function which run concurrently.
  • If there are multiple functions or a block in our application then that application is called as multithreaded application.

Important points about a Thread:-

  • Thread has its own local variable.
  • Threads share all the open files which are opened by its parent process.
  • Thread has its own stack.
  • Thread has its own CPU quantum.
  • Any thread can kill any other thread.
  • An operating system can kill any thread at any time without intimation but in case of java application role of an operating system is performed by JVM.
  • Thread can communicate with another thread by using communication methods

a)     notify()

b)    notifyAll()

c)     wait()

  • Each thread has its own priority.
  • When our thread gets scheduled, it is depend on the operating system strategies.

Different states of a Thread:-

Born state:-

  • Sin this state, thread is only created but its execution is not started.

Ready state:-

  • In this state, thread is created as well as it is ready to run but there is no CPU quantum is allocated for that state.

Running state:-

  • Thread is created and for that thread actual CPU quantum is allocated and that thread starts its life cycle for this point.

Dead state:-

  • At this state, thread executes its own function.
  • This dead state is achieved successfully or not successfully.
  • After the dead state, our thread cannot run again but in case of ready and running state thread can scheduled again and again.

e.g.

catch(InterruptException e)

{

System.out.println(e);

}

public static void main(String args[])

{

Runnable t1 = new hello(“first”);

new Threaf(t1).start();

Runnable t2 = new hello(“second”);

new Thread(t2).start();

}

Methods of Thread class:-

  • start()
  • isAlive()
  • run()
  • yield()
  • stop()
  • join()
  • sleep()

Thread information:-

  • setName()
  • getName()
  • dumpStack()
  • getThread()

Thread priorities:-

  • MIN_PRIORITY(1)
  • NORM_PRIORITY
  1. getPriority()
  2. setPriority()
  • MAX_PRIORITY(10)

Event handling:-

  • When we click on any device or when we interact with any device first signal is generated and that signal is accepted by the device driver of that device.
  • After accepting this signal device driver forward this signal to the operating system.
  • An operating system accepts that signal or an event and converts that event into a message.
  • Message is descriptive format of that event.
  • After creating the message an operating system forward that message to the currently running application.
  • To handle that event application has to provide a method which is used for handling that event.
  • Sending a message to our application means calling a method indirectly.
  • The method is used for accepting an event is called as event or an action listener method.
  • After invoking an actionListener method that method provides a specific action for that event.
  • The above model is called as delegation in java and in windows it is called as an event driven architecture.
  • When we write our own actionListener that actionListener must be registered towards an operating system or JVM.
  • This step of registering the actionListener is important because this actinListener method is called by the operating system directly.
  • To register the actionListener we can use addActionListener method.
  • After registering this method our operating system or JVM call this method when event is occurred.
  • This method is called as callback method in terms of operating system.
  • Above model is called as events and delegates in .NET.

 

Hardware/Device (signal to) ===>Device Driver (event) ===>Operating system (message) ===>JVM (event) ==>Application===>actionListener===>Approprite action is taken

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Written by Sourabh Bhunje

Sourabh Bhunje, B.E. IT from Pune University. Currently Working at Techliebe. Professional Skills: Programming - Software & Mobile, Web & Graphic Design, Localization, Content Writing, Sub-Titling etc. http://techliebe.com/about-us

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