CODEWITHSUNDEEP
javamultithreading
fool
fool

Reputation: 80

Multi-Threading in JAVA concept

 class MyThread extends Thread
    {
        public void run()
        {
            try
            {
                for(int i=0 ; i<10 ; i++)
                {
                    System.out.println("I am Lazy Thread.");
                    Thread.sleep(2000);
                }
            }
            catch (InterruptedException e)
            {
                    System.out.println("I got interrrupted.");              
            }
        }
    }
    class Test
    {
        public static void main(String[] args) 
        {
            MyThread t = new MyThread();
            t.start();        //after this line 
            t.interrupt();
            System.out.println("end of main.");
        }

    }

After t.start(); and t.interrupt(); why it is printing end of main first then the child thread statement .

According to multi threading concept it may be child class thread statement also but it is always executing the main Thread statement first .

What is the concept and working procedure behind this .Because its always executing end of main first than others.

Upvotes: 0

Views: 94

Answers (4)

Ricode
Ricode

Reputation: 75

After t.start(); there is two Thread one is main and another is child thread.

both thread are independent to each other ... : main thread initialization already done before the child thread creation and for CPU (Thread Scheduler :T.S.) its is easy to handle and execute the main thread first than the child thread. If T.S. goes for child thread execution than definitely it will takes more time to complete . There are some algorithm which works inside T.S. which threads it wants to choose first and it is always vary form T.S. to T.S.

Upvotes: 1

Prashant_M
Prashant_M

Reputation: 3124

In simple language, preparing a new thread requires a lot of initialization work. Even the main thread takes its own time to start, but because main thread is already initialized and running it completes its execution even when the threads spawned out of it is in their initialization and execution phase.

Upvotes: 1

Zulfi
Zulfi

Reputation: 586

As the docs say

public void interrupt()

Interrupts this thread.

Unless the current thread is interrupting itself, which is always permitted, the checkAccess method of this thread is invoked, which may cause a SecurityException to be thrown.

If this thread is blocked in an invocation of the wait(), wait(long), or wait(long, int) methods of the Object class, or of the join(), join(long), join(long, int), sleep(long), or sleep(long, int), methods of this class, then its interrupt status will be cleared and it will receive an InterruptedException.

If this thread is blocked in an I/O operation upon an interruptible channel then the channel will be closed, the thread's interrupt status will be set, and the thread will receive a ClosedByInterruptException.

If this thread is blocked in a Selector then the thread's interrupt status will be set and it will return immediately from the selection operation, possibly with a non-zero value, just as if the selector's wakeup method were invoked.

If none of the previous conditions hold then this thread's interrupt status will be set.

Interrupting a thread that is not alive need not have any effect.

Throws: SecurityException - if the current thread cannot modify this thread

Note : With threads you don't get any guarantee in the order of how things will be executed unless you explicitly synchronize them

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533492

why it is printing end of main first then the child thread statement .

This is because each thread run independently, which is the point.

What is the concept and working procedure behind this .Because its always executing end of main first than others.

In particular, threads take time to start, far longer than the time it takes to finish running the main() method.

You can slow down the main thread so see this happen more the way you expect.

public static void main(String[] args) throws InterruptedException {
        MyThread t = new MyThread();
        t.start();        //after this line 
        Thread.sleep(1);  // thread might not start in this time or might complete.
        t.interrupt();
        Thread.sleep(1);
        System.out.println("end of main.");
    }

In fact, 1 milli-second might be too long as a CPU can execute 3,000,000 instructions in a milli-second.

Upvotes: 4

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