synch in threads

[zaeem masood ashar]

Hello
By adding the "synchronized" keyword, the output is not synchronized i.e. "Logic" should always get printed as one word as lock on the object should ensure that the entire block is entertained before any other thread makes an attempt to enter
help needed.......

 <font size=3.0>
package thrproj;
public class Thr implements Runnable{
  Thread t;
  String g,h;
  public Thr(String name) {
  h=name;
  t=new Thread(this);
 // g=t.getName();
  t.start();
  }
  public void run(){
  meth();
    }
  synchronized void meth(){
  //Untitled1 ut1=new Untitled1();
  for (int i=0;i<3 ;i++) {
  System.out.print("Lo");
  System.out.print("gic");
  }
  System.out.print(h);
    }
  }
public class Untitled1 {
   public static void main(String[] args) {
    Untitled1 untitled11 = new Untitled1();
    new Thr("Thread A calling"+ "  ");
    new Thr("Thread B calling"+ "  ") ;
    new Thr("Thread C calling"+ "  ");
    new Thr("Thread D calling"+ "  ");
  }
  }
</font>

[This message has been edited by Cindy Glass (edited May 01, 2001).]

[Cindy Glass]

But you have 4 separate objects, each with it's own separate lock (you lock an object - not a class). Just because ONE of them is locked, does not prevent the other 3 from running indepentantly in their own threads at the same time.

[atul kashyap]

Cindy can you please explain what actually synchronization does in this example or in general.
Thanks in advance
[This message has been edited by atul kashyap (edited May 02, 2001).]

[zaeem masood ashar]

thanks
more elaboration would definitly do
Zaeem

[Cindy Glass]

I took the liberty of reworking your code so that the synchronized code is in an object other than the one that has the thread. Now I have 1 object whose class has a synchronized method and 4 threads that all try to use the one object at the same time. Each one will complete before the next begins.

<font size = 2.5>
 class Thr implements Runnable{
      Test test1;
      Thread t;
      String h;
      public Thr(String name, Test tst) {
          test1 = tst;
          h=name;
          t = new Thread(this);
          t.start();
       }
     
      public void run(){
         test1.meth();
         System.out.println(h);
      }
 }
//******************************
public class Test {

   synchronized void meth(){
   for (int i=0;i<3 ;i++) {
       System.out.print("Lo");
       System.out.print("gic");
       }
   }
   public static void main(String[] args) {
       System.out.println("Starting");
       Test myTest = new Test();
       Thr t1 = new Thr("Thread A calling"+ "  ", myTest);
       Thr t2 = new Thr("Thread B calling"+ "  ", myTest);
       Thr t3 = new Thr("Thread C calling"+ "  ", myTest);
       Thr t4 = new Thr("Thread D calling"+ "  ", myTest);
   }
}

if you remove the synchronized keyword it comes out scrambled. If you create each Thr with different myTests then it comes out scrambled.