Thread

[Abhi vijay]

Source: Devaka Coorays Exam Simulator.

    public class ThreadClass extends Thread{
 
     public ThreadClass(int x){
          this.x=x;
     }
 
     static String s="";
     static  int x=0;
 
     public static void doVIP(){
          s=s+x;
          try{
               Thread.sleep(10);
          }catch(Exception e){
               s=s+x;
          }
     }
 
     public void run(){
          synchronized(s){
               doVIP();
          }
     }
 
     public static void doDelay(long g){
          try{Thread.sleep(g);}catch(Exception e){}
     }
 
     public static void main(String args[]){
 
          ThreadClass tc1=new ThreadClass(2);
          ThreadClass tc2=new ThreadClass(1);
          ThreadClass tc3=new ThreadClass(0);
 
          tc1.start();
          doDelay(100);
          System.out.print(s);
          tc2.start();
          doDelay(100);
          System.out.print(s);
          tc3.start();
          doDelay(100);
          System.out.print(s);
 
     }
}

I dont undersatnd why its printing 000000??

When I use a single Thread instance
ThreadClass tc1=new ThreadClass(2);
the value is as expected 2.

[Preethi Dev]

Hi,

x is static and here are the steps taken

1.three constructors will run first when create them

2. since x is static the last constructor run by new ThreadClass(0),so x value will be 0 forever.

3.ex1.start();// here s=s+x will be evaluated to s="0"

4.doDelay(100) will delay the process in order to delay the main thread which prints s value.

5.same thing happen for all threads

6.when you tried ThreadClass ex1=new ThreadClass(2), static variable x will get 2 since no more constructors.


hope this helps

Thanks
Preetha

[Abhi vijay]

But why is it printing 6 times?

[Preethi Dev]

did you try this program?
you will get output as
0
00
000 not as 000000
[ December 28, 2008: Message edited by: Preetha Arun ]

[Preethi Dev]

try this ..you will get 000000 as output

public class ThreadClass extends Thread{

public ThreadClass(int x){
this.x=x;
}

static String s="";
static volatile int x=0;

public static void doVIP(){
s=s+x;
try{
Thread.sleep(10);
System.out.print(s);
}catch(Exception e){
//s=s+x;
}
}

public void run(){
synchronized(s){
doVIP();
}
}

public static void doDelay(long g){
try{Thread.sleep(g);}catch(Exception e){}
}

public static void main(String args[]){

ThreadClass tc1=new ThreadClass(2);
ThreadClass tc2=new ThreadClass(1);
ThreadClass tc3=new ThreadClass(0);

tc1.start(); doDelay(100);
tc2.start(); doDelay(100);
tc3.start(); doDelay(100);

}
}

[Punit Singh]

Arun is right here.