Short notes on Thread

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:

1. Improved performance

2. Minimized system resource usage.

3. Simultaneusly to use multiple application.

4. 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.