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Thread: synchronised

  1. #1
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    Default synchronised

    class B 
    {    
        public static synchronized void printName()
        {
            try
            {
    	           System.out.println("printName");
    	           Thread.sleep(5*1000);
            }
            catch(InterruptedException e)
            {             
            }
        }
        public synchronized void printValue()
        {      
                   System.out.println("printValue");                
        }
    }
    public class test extends Thread
    {
        B b = new B();
        public static void main(String argv[]) throws Exception
        {
    	    test t = new test();
    	    test v=new test();
    	    Thread t1 = new Thread(t,"t1");
    	    Thread t2 = new Thread(t,"t2");
    	    t1.start();
    	    t2.start();
        }  
        public void run()
        {      
            if(Thread.currentThread().getName().equals("t1"))
            {
                b.printName();
            }
            else
            {
                b.printValue();
            }       
        }   
    }
    static synchronised means locked for the class so why it is printing without any delay of 5 sec


  2. #2
    Moderators helloworld922's Avatar
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    Default Re: synchronised

    Here's how your program flow is going:
    1. main thread
    start thread 2 and thread 3
    2. t1 thread
    print out text, wait 5 seconds
    3. t2 thread
    print out text

    Because thread 2 and 3 are running concurently, thread 2's wait only affects thread two. Ex:

    // changed the run to do something in thread 2 after the wait
    if (Thread.currentThread().getName().equals("t1"))
    {
         b.printName();
         System.out.println("done waiting!");
    }...

    After running this, you'll see:

    printName
    printValue
    done waiting!

    Also, fyi if all you're running is a static method, you don't need to create a B object in your main class. Call the static method using the class name.

    B.printName();
    B.printValue();

  3. #3
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    Default Re: synchronised

    no its not locking the object in case of static synchronised
    in case of static
    the output is
    printname
    printvalue
    donewaiting
    why

  4. #4
    Moderators helloworld922's Avatar
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    Default Re: synchronised

    The static refers to a class state, not a specific instanced object. So, any static methods are locked to the static synchronized method, but all instance methods are left unlocked. See Instrinsic Locks and Synchronization (second section).

  5. #5
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    Default Re: synchronised

    nice post!
    -------
    Greensboro Press Release Service