Threads

A thread is a lightweight sub process, a smallest unit of processing. It is a separate path of execution.

Threads are independent, if there occurs exception in one thread, it doesn't affect other threads. It shares a common memory area.

Thread is executed inside the process.

Thread life cycle

Ways of creating threads in java


Example 1,

Implements Runnable interface,

class MyThread implements Runnable
{
 public void run()
 {
  System.out.println("concurrent thread started running..");
 }
}

class MyThreadDemo
{
 public static void main( String args[] )
 {
  MyThread mt = new MyThread();
  Thread t = new Thread(mt);
  t.start();
 }
}

Output : concurrent thread started running..

By Extending Thread class,

class MyThread extends Thread
{
 public void run()
 {
  System.out.println("Concurrent thread started running..");
 }
}

classMyThreadDemo
{
 public static void main( String args[] )
 {
  MyThread mt = new  MyThread();
  mt.start();
 }
}

Output : concurrent thread started running..

Note on creating threads,

Using the Thread class directly has the following disadvantages.

• Creating a new thread causes some performance overhead
• Too many threads can lead to reduced performance, as the CPU needs to switch between these threads.
• You cannot easily control the number of threads, therefore you may run into out of memory errors due to too many threads.