What are thread.

Multithreading refers to two or more tasks executing concurrently within a single program. A thread is an independent path of execution within a program. Many threads can run concurrently within a program. Every thread in Java is created and controlled by the java.lang.Thread class. A Java program can have many threads, and these threads can run concurrently, either asynchronously or synchronously.

Multithreading has several advantages over Multiprocessing such as;

• Threads are lightweight compared to processes
• Threads share the same address space and therefore can share both data and code
• Context switching between threads is usually less expensive than between processes
• Cost of thread intercommunication is relatively low that that of process intercommunication
• Threads allow different tasks to be performed concurrently.

Life cycle of a Thread

1. New : A thread begins its life cycle in the new state. It remains in this state until the start() method is called on it.
2. Runable : After invocation of start() method on new thread, the thread becomes runable.
3. Running : A method is in running thread if the thread scheduler has selected it.
4. Waiting : A thread is waiting for another thread to perform a task. In this stage the thread is still alive.
5. Terminated : A thread enter the terminated state when it complete its task.