System.out.println("hey got it...."); never executed in my program
I can understand its because of synchronized keyword but what is actually happening with that.
TestJoin class called from CFG class and the problem is in this class
class TestJoin implements Runnable{
public String x;
TestJoin(String x){
this.x= x;
}
public void testJoin() {
System.out.println("b4"+x);
synchronized(x) {
System.out.println(x);
ThreadJoining t1 = new ThreadJoining("2");
// thread t1 starts
t1.start();
System.out.println("you fool");
try{
System.out.println(
"Current Thread: "+
Thread.currentThread().getName()
);
t1.join();
//never this line is executed
System.out.println("hey got it....");
}catch(Exception ex){
System.out.println(
"Exception has " +
"been caught" + ex
);
}
}
}
@Override
public void run() {
testJoin();
}
}
Simply creating another thread its called from TestJoin class
class ThreadJoining extends Thread{
String c;
ThreadJoining(String co){
c=co;
}
@Override
public void run()
{
synchronized(c) {
for (int i = 0; i < 2; i++){
try{
Thread.sleep(500);
System.out.println(
"Current Thread: " +
Thread.currentThread().getName()
);
}catch(Exception ex){
System.out.println(
"Exception has" +
" been caught" + ex
);
}
System.out.println(i);
}
}
}
}
Main class execution starts from here
public class GFG{
public static void main (String[] args){
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
System.out.println("Bye Bye");
}
});
new Thread(new TestJoin("1")).start();
new Thread(new TestJoin("1")).start();
new Thread(new TestJoin("2")).start();
new Thread(new TestJoin("3")).start();
}
}
output for the above execution
b41
1
b43
3
b42
2
b41
you fool
Current Thread: Thread-4
you fool
Current Thread: Thread-1
you fool
Current Thread: Thread-3
Second Edit:
The above issue is only if I synchronize with string or singleton object, if I use a new object Its perfectly file
Example, with normal object synchronization
public class GFG{
public static void main (String[] args){
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
System.out.println("Bye Bye");
}
});
Sample s = new Sample();
new Thread(new TestJoin(s)).start();
new Thread(new TestJoin(s)).start();
new Thread(new TestJoin(new Sample())).start();
new Thread(new TestJoin(new Sample())).start();
}
}
public class TestJoin implements Runnable{
public Sample x;
TestJoin(Sample x){
this.x= x;
}
public void testJoin() {
System.out.println("b4"+x);
synchronized(x) {
System.out.println(x);
ThreadJoining t1 = new ThreadJoining("2");
// thread t1 starts
t1.start();
System.out.println("you fool");
try
{
System.out.println("Current Thread: "
+ Thread.currentThread().getName());
t1.join();
System.out.println("hey got it....");
}
catch(Exception ex)
{
System.out.println("Exception has " +
"been caught" + ex);
}
}
}
@Override
public void run() {
testJoin();
}
}
class ThreadJoining extends Thread{
String c;
ThreadJoining(String co){
c=co;
}
@Override
public void run(){
synchronized(c) {
for (int i = 0; i < 2; i++){
try{
Thread.sleep(500);
System.out.println(
"Current Thread: " +
Thread.currentThread().getName()
);
}catch(Exception ex){
System.out.println(
"Exception has" +
" been caught" + ex
);
}
System.out.println(i);
}
}
}
}
public class Sample {
}
Output
b4Sample@a5c4778
b4Sample@27efa2ad
b4Sample@a5c4778
b4Sample@27507837
Sample@27507837
Sample@27efa2ad
Sample@a5c4778
you fool
you fool
Current Thread: Thread-4
you fool
Current Thread: Thread-3
Current Thread: Thread-1
Current Thread: Thread-6
0
Current Thread: Thread-6
1
hey got it....
Current Thread: Thread-5
0
Current Thread: Thread-5
1
hey got it....
Current Thread: Thread-7
0
Current Thread: Thread-7
1
hey got it....
Sample@a5c4778
you fool
Current Thread: Thread-2
Current Thread: Thread-8
0
Current Thread: Thread-8
1
hey got it....
Bye Bye
