1. Multi-Threading in Java

2. Thread Thread: a flow of control in a program In Java,
Process: a running instance of a program including all variables and other states
In Java,
Application: the Java interpreter starts a thread for the main method.
Applet: the Web browser starts a thread to run the applet.
Java has built-in support for multi-threading.

3. A typical program Multi-Thread Start Task1 Task2 Task1 Task2 Task3
Stop
Stop

4. Multi-Threading
Multi-threading is the capability of running multiple tasks concurrently within a program.
Multi-threading can make your program more responsive and interactive, and run faster than a non-threaded version.
Issues
Prioritization
Synchronization

5. Creating Thread Thread class Example
Extend Thread class and override the run method
Example
class SimpleThread extends Thread {
            public void run() {
            // work for thread
          }
       }
SimpleThread t = new SimpleThread () ;// create thread
t.start(); // begin running thread

6. Runnable interface Example
Create object implementing Runnable interface
Pass it to Thread object via Thread constructor
Example
class SimpleThread extends Frame
implements Runnable {
            public void run() {
            // work for thread
          }
       }
Thread t = new Thread(new SimpleThread()); // create thread
t.start(); // begin running thread

7. Life cycle of Thread new start new ready I/O complete, time-out,
notify, resume
yield
(dispatch)
running
blocked
Yield --- a thread may be in queing status which is controlled by java runtime scheduler.
I/O, sleep,
wait, suspend
terminate
dead

8. Overview of the Thread Methods
run():void
start():void – to make a Thread eligible for use
sleep():void – to make a Thread inactive
interrupt():void – to interrupt a running Thread
isAlive():boolean – to check status of a Thread
Other methods
Stop(), setPriority(p: int), wait(), notify()…

9. Examples MyThread PriThread Show simple multi-threading
Use the method setPriority(p: int)

10. Thread Synchronization
To avoid resource conflicts, may synchronize method invocation so that only one thread can access a method at a time.
Keyword synchronized
Only one thread at a time to execute statements within synchronized blocks.
All other threads block until the method finishes.
If several synchronized statements are trying to execute on an object at the same time, only one of them is active on the object.
Example: ConcurrenyDemo