- Threads are lightweight processes that can be executed concurrently within a process to improve responsiveness and resource utilization. - Threads share the same memory as the process they belong to, making communication between threads cheaper than between processes. - The main() method represents the initial thread when a Java program starts. Additional threads can be created by extending the Thread class or implementing the Runnable interface.

1. 
THREADING CONCEPTS
by
U.Raheema parveen

2. 
 Light weight process
 Smallest unit of processing
 Share some memory area of the process
 Thread is executed inside the process
 Executing multi threads simultaneously
WHAT IS THREAD

3. 
WHAT IS MULTITHREADING
Multi processing Multi threading
Separate memory space Share same memory
Heavy weight Light weight process
Time and cost is more Less cost and time

4. 
 Threads are light weight process
Because they share same memory space for child
threads too. whereas process , do not allocate same
memory space.
 Interthread communication is in expensive
 Context switching of threads are in expensive
 Process inside the interthread and context sensitive is
costly
Advantages of threads

5. 
 Threads are implemented in the form of objects that
contain a method is called run() method is the heart
and soul of any thread
public void run()
{
………. (statement for implementing thread)
……….
}
Creating threads

6. 
 The run() method should be invoked by an object of the
concerned thread.
 This can be achieved by creating the thread the initiating it
with help of another thread method called start().
 Following two ways
By creating a thread class: A class that extends thread class and
override its run() method with the code required method
Creating threads-con’d

7. 
 By converting a class to a thread: Define a class that
implements Runnable interface. The Runnable
interface has only one method , run() that is to be
defined in the method the code to be executed by the
thread
Creating threads-con’d

8.  Declare the class as extending the thread class
 Implement the run() method
 Create a thread object and call the start() method to initiate the
thread execution
Declaring the class
the thread class can be extended as follows
Class MyThread extends Thread
{
………….
………….
………….
}
Extending the thread class

9. 
Implementing the run() method:
 The run() method has been inherited by the Mythread.
 This method in order to implement the code to be executed by
our thread.
 The basic implementation of run() like
public void run()
{
………
………
………
}
Extending the thread class

10. 
Starting new thread:
to actually create and run an instance of our thread class
MyThread aThread = new MyThread();
aThread.start();
 New objects of class MyThread, the thread will be
Newborn state.
 The start() method to move into the runnable state
Extending the thread class

11. class MultithreadingDemo extends Thread{
public void run()
{
System.out.println("My thread is in running state.");
}
public static void main(String args[])
{
MultithreadingDemo obj=new MultithreadingDemo();
obj.start();
} }
Output:
 My thread is in running state.
Example program

12. 
Life cycle

13.  We create a thread object, the
thread is born and is said to be
in newborn state.
 The thread is not yet scheduled
for running
Following things
 Schedule it for running using start() method
 Kill it using stop() method
Life cycle – New born state

14. 
 The running state means that the thread is ready for execution
and is waiting for the availability of the process
 The thread has joined the queue of threads they are waiting for
execution
 The process of assigning time to thread is called a time slicing
 We can using the yield() method
Life cycle – Runnable state

15. 
Running means the process has been time to the thread for
execution
Following situations
1. It has been suspended using suspend() method. A
suspended thread can be revived by using the resume()
method.
2. It has been made to sleep. We can a thread to sleep for a
specified time period using the method sleep(time).where
time is in milliseconds
Life cycle –Running state

16. 
3. It has been hold to wait until some event occurs. This
is done using wait() method. The thread can be
scheduled to run again for the notify() method.
Running state-con’d

17. 
 A thread is said to be blocked when it is prevented
from entering into the runnable state and
subsequently the running state.
 The thread is suspended, sleeping, or waiting in
order to satisfy certain requirement.
 A blocked thread is “not runnable” but not dead it
has access to run again.
Life cycle-blocked state

18. 
 A running thread ends its life when it has completed
executing its run() method.
 It is natural death
 A thread can be killed as soon it is born , or while it
is running ,or even when it is “not runnable”
(blocked) condition.
Life cycle-Dead state

19. 
 It can be default running
 When a program begins , one thread begins running
immediately
Importance of main threads
 A thread from which other “child” thread can be created
 Must be the threads to finish execution
 Current Thread() returns reference to the current thread
 It is public and static in nature thread objects
Main thread

20. 
 getName – get in thread name
 getPriority – thread get priorities
 isAlive – check if a thread is still running
 Join – wait for a thread to terminated
 run – entry point for the thread
 sleep – suspend a thread for a period of time
 start() – start a thread by calling its run method
Thread methods

21. 
 The call to sleep() method is enclosed in a try block
and followed by a catch block. This is necessary
because the sleep() method throws an exception. if
we fail to catch the exception, program will not
compile.
 Syntax
Catch(threadDeath e) {
……..
……..
}
Thread execptions

22. Catch(InterruptedException e)
{
………..
………..
}
Catch(Illegal ArgumentException e)
{
………..
………..
}
Catch(Exception e)
{
………..
………..
}
Thread exceptions-con’d

23. 
 thread scheduler assigns processor to a thread based on
priority of thread.
 Whenever we create a thread in Java, it always has some
priority assigned to it.
 Java is set the priority is using method is setpriority()
method.
ThreadName.setPriority(intNumber);
The intNumber is an integer value
Thread priority

24. 
 public static int MIN_PRIORITY: This is minimum
priority that a thread can have. Value for this is 1.
 public static int NORM_PRIORITY: This is default
priority of a thread if do not explicitly define it.
Value for this is 5
 public static int MAX_PRIORITY: This is maximum
priority of a thread. Value for this is 10.
Priority-con’d

25.  Capability to control the access of multiple threads to a
shared resource
Why?
 To prevent the interference of threads
 To prevent consistency problems.
 Understanding locks
 Every object has a lock or monitor.
 A thread needs to acquire lock before accessing objects
Types
Process ,Thread
synchronization

26. Mutual extension Co-operation
Keeps threads from
interfering with one another
while sharing data
 Synchronized method
 Synchronized block
 Static synchronization
Inter-thread communication
 synchronized threads to
communicate with each
others
Thread synchronization

27. 
 We can create two ways
 Using the extended Thread class
 Implementing the Runnable interface
The Runnable interface declares the run()
Method that is required for implementing threads in
programs.
Runnable interface

28. 
 Following steps
 Declare the class as implementing the Runnable
interface.
 Implement the run() method.
 Create a thread by defining an object that is
instantiated from “runnable” class as the target of
the thread
 Call the thread start() method to run the thread.
Runnable interface

29. class MultithreadingDemo implements Runnable
{
public void run()
{
System.out.println("My thread is in running state.");
}
public static void main(String args[])
{
MultithreadingDemo obj=new MultithreadingDemo();
Thread tobj=new Thread(obj);
tobj.start();
} }
Output:
 My thread is in running state.
Runnable interface-example program

30. 
Thank you