Threads are **** confusing.. pls help...
This code i was going through is very confusing. I have synchronized the String object sa which is in class B. I am then creating a thread of class A, and passing the object sa to class A. Only after having passed the object am i changing the value of String object in class B, how does it get reflected in class A's object. Whats happening here?
class Aextends Thread{
String[] sa;
public A(String[] sa){this.sa = sa;}
publicvoid run(){
synchronized (sa){System.out.print(sa[0] + sa[1] + sa[2]);}
}}
publicclass B{
publicstaticvoid main (String[] args){
String[] sa =new String[]{"X","Y","Z"};
synchronized (sa){
Thread t1 =new A(sa); t1.start();
sa[0] ="A"; sa[1] ="B"; sa[2] ="C";
}}}
[1822 byte] By [
KartikVa] at [2007-10-1 5:48:17]
synchronized (sa) {
Thread t1 = new A(sa); t1.start();
sa[0] = "A"; sa[1] = "B"; sa[2] = "C";
}
In the above piece of code, am i not creating Thread t1and passing object sa to it. So doesnt that mean that the String array with values XYZ have been passed to t1 object. Only after passing the above string array with XYZ am i changing values in sa of class B to A,,B,C. I do understand that it is a synchronized block, so thread t1 will have to wait for this block to complete, but that does not mean that the thread t1 would not have been created with String XYZ and be ready to this synchronization block to complete. This is my understanding and am sure i am wrong somewhere coz the output is totally different from what i preceive.
Please let me know ...
Thanks.
Aha..
THAT BIT OF PRODDING WILL DO.....
thanks :) (jhmm.. was expecting something complex and missed out on the basics)..
public class StringTest {
static void m1 (String a[]){
System.out.println("The values of a are " + a[0] + a[1]);
}
public static void main(String[] args) {
String s[] ={"a1","a2","a3"};
m1(s);
s[0]="3";
m1(s);
}
}
> This code i was going through is very confusing. I
> have synchronized the String object sa which is in
> class B. I am then creating a thread of class A, and
> passing the object sa to class A. Only after having
> passed the object am i changing the value of String
> object in class B, how does it get reflected in class
> A's object. Whats happening here?
>
class A extends Thread {
String[] sa;
public A(String[] sa) {this.sa = sa;}
public void run() {
/*
Here the the thread will wait until this thread obtain the monitor of sa
to do so it will have to wait until the main releases the monitor
but when main releases the monitor the value of sa is set to ABC
*/
synchronized (sa) {
// so this will print ABC
System.out.print(sa[0] + sa[1] a[1] + sa[2]);
}
}}
public class B {
public static void main (String[] args) {
String[] sa = new String[]{"X","Y","Z"};
/* Here you are obtaining the monitor of sa
and run method of other thread cant obtain the monitor
until this thread releases it */
synchronized (sa) {
Thread t1 = new A(sa); t1.start();
// Above line dosent mean that thread A get started immedeatly
//still the active thread is main
// so at the time when following line is executed
// the thread A may not even started its run
sa[0] = "A"; sa[1] = "B"; sa[2] = "C";
}
//this is where you release the monitior
// and then only your other thread can obtain the monitor of sa
// but its too late now since sa has values ABC
}}
LRMKa at 2007-7-9 14:02:16 >
