Advanced Java Programming - Old Questions
9. Write down the life cycle of thread. Write a program to execute multiple threads in priority base. [2+3]
Answer
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Life Cycle of Thread
A thread in Java at any point of time exists in any one of the following states.
- New: A new thread begins its life cycle in the new state. It remains in this state until the program starts the thread. It is also referred to as a born thread. In simple words, a thread has been created, but it has not yet been started. A thread is started by calling its start() method.
- Runnable: The thread is in the runnable state after the invocation of start() method, but the thread scheduler has not selected it to be the running thread. A thread starts life in the Ready-to-run state by calling the start method and wait for its turn. The thread scheduler decides which thread runs and for how long.
- Running: When the thread starts executing, then the state is changed to a “running” state. The scheduler selects one thread from the thread pool, and it starts executing in the application.
- Dead: This is the state when the thread is terminated. The thread is in running state and as soon as it completed processing it is in “dead state”. Once a thread is in this state, the thread cannot even run again.
- Blocked (Non-runnable state):This is the state when the thread is still alive but is currently not eligible to run. A thread that is blocked waiting for a monitor lock is in this state. A running thread can transit to one of the non-runnable states depending on the situation. A thread remains in a non-runnable state until a special transition occurs. A thread doesn’t go directly to the running state from a non-runnable state but transits first to the Ready-to-run state.
Program to execute multiple threads in priority base
class First extends Thread
{
@Override
public
void run()
{
for
(int i = 1; i <= 10; i++)
{
System.out.println(i);
}
}
}
class Second extends Thread
{
@Override
public
void run()
{
for
(int i = 11; i <= 20; i++)
{
System.out.println(i);
}
}
}
class Third extends Thread
{
@Override
public
void run()
{
for
(int i = 21; i <= 30; i++)
{
System.out.println(i);
}
}
}
public class ThreadPriority
{
public
static void main(String[] args) throws InterruptedException
{
Thread t1 = new First();
Thread t2 = new Second();
Thread t3 = new Third();
t1.setPriority(Thread.MAX_PRIORITY);
t2.setPriority(Thread.MIN_PRIORITY);
t3.setPriority(Thread.NORM_PRIORITY);
t1.start();
t2.start();
t3.start();
}
}