What will be the output....Please explain

[Tamanna Mittal]

public class myclass extends Thread {
static String a="Test";
public static void main(String[] args){
myclass m=new myclass();
m.amethod(a);
System.out.println(a);
}
public void amethod(String a){
a = a+" thread";
start();
}
public void run(){
for(int i=0;i<4;i++){
a = a+" "+i;
}
}
}
------------------
Cheers
Tamanna :-)

[Vanitha Sugumaran]

Hi,
The output of this program will be Test.
When we pass String a to amethod, I think it is considered as a local variable in that method.
if you change your code like this, then the value of a is assigned to Test Thread.

public class myclass extends Thread {
 static String a="Test";
public static void main(String[] args){
myclass m=new myclass();
m.amethod(a);
System.out.println(a + "  from main");
}
public void amethod(String s){
a = s+" thread";
System.out.println(a + "  from amethod");
start();
}
public void run(){
for(int i=0;i<4;i++){
a = a+" "+i;
}
}
}

Vanitha.

[Tamanna Mittal]

Yes i got it. Also I am confused that in the run method when we are accessing the static variable directly. Still it is showing the initaial value "test thread' and not the int values added to the string why is it so? can somebody explain it to me please.

[Tamanna Mittal]

Also vanitha
if i compile and run the under given code it gives me a different output. but the only difference here is that i have added 2 print statements in the original code.
public class myclass1 extends Thread {
static String a="Test";
public static void main(String[] args){
myclass1 m=new myclass1();
m.amethod(a);
System.out.println(a + " from main");
}
public void amethod(String s){
a = s+" thread";
System.out.println(a + " from amethod");
start();
System.out.println(a);//1 new print statement.
}
public void run(){
for(int i=0;i<4;i++){
a = a+" "+i;
}
System.out.println(a);//2 new print statement.
}
}
Output:
Test thread from amethod
Test thread 0 1 2 3
Test thread 0 1 2 3
Test thread 0 1 2 3 from main
Y is it so that just by adding 2 print statements the output in the main function is changing.

[Vanitha Sugumaran]

Hi Tamanna,
I also added 2 lines, but I got different outputs,
Test thread from amethod
Test threadfrom amethod after start
Test thread from main
Test thread 0 1 2 3
The reason is , main() is a seperate thread, and we start another another thread from amethod, so there are 2 threads with same priority.
which thread will run first depends on the system. if amethod thread starts first, the output will be like your output.
In my case I think the main thread got invoked first so I got the this output.(a 's value didn't have 0..3 from main)
If I yield() from the main the output is like this,
Test thread from amethod
Test threadfrom amethod after start
Test thread 0 1 2 3 from run
Test thread 0 1 2 3 from main

public class myclass extends Thread {
static String a="Test";
public static void main(String[] args){
myclass m=new myclass();
m.amethod(a);
Thread t = Thread.currentThread();
t.yield();
System.out.println(a + " from main");
}
public void amethod(String s){
a = s+" thread";
System.out.println(a + " from amethod");
start();
System.out.println(a + "from amethod after start");//1 new print statement.
}
public void run(){
for(int i=0;i<4;i++){
a = a+" "+i;
}
System.out.println(a + " from run");//2 new print statement.
}
}

Correct me, if I am wrong,
Vanitha.

[Tamanna Mittal]

Nopes i ma not getting the point Y u made another instance of thread class. Can u please explain it to me again coz., i am getting the same output as u even after hiding those lines which u have entered. this is really confusing.

[Vanitha Sugumaran]

I am sorry, We can just add yield() method, we don't have to get the current thread.
if I comment the yield() my o/p is
Test thread from amethod
Test threadfrom amethod after start
Test thread from main
Test thread 0 1 2 3 from run
if I add yield() my o/p is
Test thread from amethod
Test threadfrom amethod after start
Test thread 0 1 2 3 from run
Test thread 0 1 2 3 from main
Vanitha.