Que on thread

[sanjana narayanan]

Hi,
This program was already posted but i have more questions on the program.

class thread implements Runnable
{
StringBuffer s1=new StringBuffer("Suresh");
StringBuffer s2=new StringBuffer("babu");
public void run()
{
new Thread()
{
public void run()
{

System.out.println("In first run");
synchronized (s1)
{
s1.append("s");
synchronized(s2)
{
s2.append("a");
}
System.out.println(s1);
System.out.println(s2);
}
} 
}.start();
new Thread(){
public void run()
{
System.out.println("In second run");

synchronized (s1)
{
s1.append("M");
synchronized(s2)
{
s2.append("N");
}
System.out.println(s1);
System.out.println(s2);
}
}
}.start();
}
public static void main(String args[])
{
Thread t=new Thread(new thread(),"Impthread");
t.start();
}
}
  

1.How many threads are created in the program?
2. Output is
In first run
In second run
sureshs
babua
sureshM // why is sureshM and not sureshsM
babuaN // here N is getting appended to babua and not to babu
Not sure abt the output.

Any explanation would be appreciated?
-Sanjana

[David Hadiprijanto]

Hi Sanjana,

1. How many threads are created in the program?

I think there are 3 threads created, on line 5, 10, and 11.
[I re-pasted your code below, it was rather difficult to read your posted code ]
About the output, I don't think it is possible to get the output as you described. Since both the s1.append(); and s2.append(); (line 1, 2, 6, and 7) are synchronized using s1 and s2, if you get Sureshs then you should get babua, SureshsM, and babuaN. Another possibility is you get SureshM, then you will get babuN, SureshMs, and babuNa - if "In second run" thread get to line 6 before "In first run" thread get to line 1. (Using the Thread.sleep method on line 0 to force the "In first run" thread to execute the s1.append() after "In second run" thread).
When I try your code (without the Thread.sleep on line 0), I happen to get :
In first run
Sureshs
babua
In second run
SureshsM
babuaN

 
class thread implements Runnable {
  StringBuffer s1=new StringBuffer("Suresh");
  StringBuffer s2=new StringBuffer("babu");
  public void run(){
    new Thread() {
      public void run(){
        System.out.println("In first run");
        /* line 0
        try { Thread.sleep(1000); } 
        catch (InterruptedException ie) {} 
        */
        synchronized (s1) {
          s1.append("s");                        // line 1
          synchronized(s2) {
            s2.append("a");                      // line 2
          }
          System.out.println(s1);                // line 3
          System.out.println(s2);                // line 4
        }
      }
    }.start();                                   // line 5
    new Thread() {
      public void run() {
        System.out.println("In second run");
        synchronized (s1) {
          s1.append("M");                       // line 6
          synchronized(s2) {
            s2.append("N");                     // line 7
          }
          System.out.println(s1);               // line 8
          System.out.println(s2);               // line 9
        }
      }
    }.start();                                  // line 10
  }
  public static void main(String args[]) {
    Thread t = new Thread(new thread(), "Impthread");  // line 11
    t.start();
  }
}