Java Multi-threading programming

Multithreading allows concurrent execution of two or more process or threads of a program for maximum utilization of CPU and increase the throughput

1. Multithreading Programming
Multithreading is conceptual programming where a
program (processes) are divided into two or more
subprograms (processes).
A thread is similar to program that has a single flow of
control
It has beginning , body , an end and executes command
Sequentially
Every program will have at least one thread.
1 RAJESHREE KHANDE

2. What are Threads?
A piece of code that run in concurrent with other
threads.
Each thread is a statically ordered sequence of
instructions.
Threads are being extensively used express
concurrency on both single and multiprocessors
machines.
2 RAJESHREE KHANDE

3. A single threaded program
class ABC
{
….
public void main(..)
{
…
..
}
}
begin
body
end
3 RAJESHREE KHANDE

4. A Multithreaded Program
Main Thread
Thread A Thread B Thread C
start
start
start
Threads may switch or exchange data/results
Main Method
Module
Switching
Switching
4 RAJESHREE KHANDE

5. Printing Thread
Editing Thread
Modern Applications need Threads (ex1):
Editing and Printing documents in background.
5 RAJESHREE KHANDE

6. Thread Class
Multithreading System built upon Threadclass it’s method,
it’s interface Runnable.
To create a new Thread , either extends Threador
implement the Runnable interface
Thread class defines several Methods. Some of the method
are
1) getName():Obtain a thread Name.
6 RAJESHREE KHANDE

7. Thread Class
2) getPriority() :Obtain a Thread Priority
3) isAlive() :Determine if the thread is still running
4) join() :Wait for thread to terminate.
5) run() :Entry point for the thread.
6) sleep() :Suspend a thread for a period of time.
7) start() :Start a thread by calling it’s run()
method
7 RAJESHREE KHANDE

8. Creating Thread
Java threads may be created by:
1. Extending Thread class
2. Implementing the Runnable interface
Java threads are managed by the JVM.
8 RAJESHREE KHANDE

9. 1. Extending Thread class
Declare a classas extending the Threadclass
Create instance of that class
This class must override the run()method which is
entry point for the new thread.
It must also call start()to begin the execution of new
thread.
9 RAJESHREE KHANDE

10. Extending Thread class
Syntax
class MyThread extends Thread
{
public void run()
{
// thread body of execution
}
}
10 RAJESHREE KHANDE

11. Create a thread:
MyThread thr1 = new MyThread();
Start Execution of threads:
thr1.start();
Create and Execute:
new MyThread().start();
1.Extending Thread class
11 RAJESHREE KHANDE

12. The Main Thread
When Java Program start up one thread begins
immediately called Main Thread.
It can be control through a object Thread
For this obtain a reference to it by calling the method
currentThread()which is public staticmember of Thread
It’s General Form
static Thread CurrentThread()
12 RAJESHREE KHANDE

13. Life Cycle of Thread
13
new
runnable non-runnable
dead
wait()
sleep()
suspend()
blocked
notify()
slept
resume()
unblocked
start()
stop()
RAJESHREE KHANDE

14. 2: Threads by implementing Runnable interface
class MyThread implements Runnable
{
.....
public void run()
{
// thread body of execution
}
}
Creating Object:
MyThread myObject = new MyThread();
Creating Thread Object:
Thread thr1 = new Thread( myObject );
Start Execution:
thr1.start();
14 RAJESHREE KHANDE

15. An example
15
class MyThread implements Runnable
{
public void run()
{
System.out.println(" this thread is running ... ");
}
} // end class MyThread
class ThreadEx2
{
public static void main(String [] args ) {
Thread t = new Thread(new MyThread());
// due to implementing the Runnable interface
// I can call start(), and this will call run().
t.start();
} // end main()
} // end class ThreadEx2
RAJESHREE KHANDE