Process
A process runs independently and isolated of other processes. It cannot directly access shared data in other processes. The resources of the process, e.g. memory and CPU time, are allocated to it via the operating system.
Thread
Threads are sometimes called lightweight processes. Both processes and threads provide an execution environment, but creating a new thread requires fewer resources than creating a new process. Threads exist within a process — every process has at least one. Threads share the process’s resources, including memory and open files. This makes for efficient, but potentially problematic, communication.
Defining and Starting a Thread
By implementing the Runnable Interface
public class HelloRunnable implements Runnable
{
public void run()
{
System.out.println("Hello from a thread!");
}
public static void main(String args[])
{
(new Thread(new HelloRunnable())).start();
}
}
By extending the Thread class
public class HelloThread extends Thread
{
@Override
public void run()
{
System.out.println("Hello from a thread!");
}
public static void main(final String args[])
{
(new HelloThread()).start();
}
}