Java - Tips n Tricks

• Runnable — waiting for its turn to be picked for execution by the thread schedular based on thread priorities.
  
• Running: The processor is actively executing the thread code. It runs until it becomes blocked, or voluntarily
• gives up its turn with this static method Thread.yield(). Because of context switching overhead, yield() should not be used very frequently.
  
• Waiting: A thread is in a blocked state while it waits for some external processing such as file I/O to finish.
• Sleeping: Java threads are forcibly put to sleep (suspended) with this overloaded method: Thread.sleep(milliseconds), Thread.sleep(milliseconds, nanoseconds);
• Blocked on I/O: Will move to runnable after I/O condition like reading bytes of data etc changes.
• Blocked on synchronization: Will move to Runnable when a lock is acquired.
• Dead: The thread is finished working.

Creation of Thread:

Threads can be used by either :

• Extending the Thread class
• Implementing the Runnable interface.

class Counter extends Thread {

//method where the thread execution will start
public void run(){
//logic to execute in a thread
}

//let’s see how to start the threads
public static void main(String[] args){
Thread t1 = new Counter();
Thread t2 = new Counter();
t1.start(); //start the first thread. This calls the run() method
t2.start(); //this starts the 2nd
thread. This calls the run() method
}
}
class Counter extends Base implements Runnable {

//method where the thread execution will start
public void run(){
//logic to execute in a thread
}

//let us see how to start the threads
public static void main(String[] args){
Thread t1 = new Thread(new Counter());
Thread t2 = new Thread(new Counter());
t1.start(); //start the first thread. This calls the run() method
t2.start(); //this starts the 2nd
thread. This calls the run() method
}
}