Thread:
A Thread is a path of execution of a program. A thread is a sequence of instructions that executed in a define unique flow of control.
SingleThread: A process is made up of one thread.
MultiThread: A process is made up of two or more thread.
Multitasking: It is a ability to do two or more tasks at a same time.
Create a Thread
-> extends Thread class
-> implements Runnable interface (its to be more useful because in big projects super class to be reserved one)
Process based:
It enables a computer to create more process concurrently. Each process having separate memory address location. So switches from one process to another , processor have face more overloads.
Thread based:
A program cotains more threads , it can do more tasks simultaneusly.
A processor switches from one thread to another with fewer overloads. It is also called as Light process.
Advantage:
Improved performance
Minimized system resource usage.
Simultaneusly to use multiple application.
Program structure simplification.
DisAdvantage:
Race condition: When two or more threads try to access the same variable atleast one thread should to write that variable before to access. Its arised because of lack of synchronization.
DeadLock: When two threads are waiting for each other for complete their operation before complete their individual actions.
Lock-starvation: While execution of thread postponed because of that low priority. Java runtime environment executes the thread based on priority. Because CPU executes one thread at a time. Thread priority value 1-10.
Life Cycle:
1.New: While thread initialized it will enter to init state. After we should call start() method, Otherwise it will cause IllegalThreadStateException.
2.Runnable: Once start method called then it will enter to runnable state. Start method allocate each thread resource and sheduldes it ,then it will call run() method.
3.NotRunnable: 3 ways
-> sleep() - wait for specified time.
-> wait() - wait until notify.
-> Blocked by another thread – Blocked thread while I/O opeartion.
4.Dead: if run method completed or thread object to be asign to null then its enter to this state.
Synchronization: Used to avoid racecondition or deadLock effects . Synchronization means serializing the threads. It allows to execute one thread at a time.
