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.
Thread Creation
There are two ways to create thread in java;
Implement the Runnable interface (java.lang.Runnable) By Extending the Thread class (java.lang.Thread)
Implementing the Runnable Interface
The Runnable Interface Signature
public interface Runnable {
void run();
}
One
way to create a thread in java is to implement the Runnable Interface
and then instantiate an object of the class. We need to override the
run() method into our class which is the only method that needs to be
implemented. The run() method contains the logic of the thread.
The procedure for creating threads based on the Runnable interface is as follows:
1.
A class implements the Runnable interface, providing the run() method
that will be executed by the thread. An object of this class is a
Runnable object.
2. An object of Thread class is created by
passing a Runnable object as argument to the Thread constructor. The
Thread object now has a Runnable object that implements the run()
method.
3. The start() method is invoked on the Thread object
created in the previous step. The start() method returns immediately
after a thread has been spawned.
4. The thread ends when the run() method ends, either by normal completion or by throwing an uncaught exception.
Below
is a program that illustrates instantiation and running of threads
using the runnable interface instead of extending the Thread class. To
start the thread you need to invoke the start() method on your object.
