Q- How to Run Threads in Sequence? Or How to Run Threads in Sequence without join? Or How to make sure sequence of threads in java?
Example - 1 : Using Join() method.
public class ThreadSequenceUsingJoin {
public static void main(String[] args) {
Worker worker = new Worker();
// Three threads
Thread t1 = new Thread(worker);
Thread t2 = new Thread(worker);
Thread t3 = new Thread(worker);
try {
// First thread
t1.start();
t1.join();
// Second thread
t2.start();
t2.join();
// Third thread
t3.start();
t3.join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class Worker implements Runnable {
@Override
public void run() {
System.out.println("In run method " + Thread.currentThread().getName());
}
}
Output
In run method Thread-0
In run method Thread-1
In run method Thread-2
Example - 2 :Without using Join() method.
public class Thread1 extends Thread {
ThreadController threadControler;
int sequence;
public Thread1(ThreadController threadControler, int sequence) {
this.threadControler = threadControler;
this.sequence = sequence;
}
@Override
public void run() {
while (true) {
synchronized (threadControler) {
if (threadControler.getCount() != sequence) {
/*
* System.out.println("In thred --- Thread1 : Count is " +
* threadControler.getCount() + ", Sequence is " + sequence);
*/
try {
threadControler.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else if (threadControler.getCount() == sequence) {
System.out.println(
"Print :: Thread1, Count is " + threadControler.getCount() + ", Sequence is " + sequence);
threadControler.incrementCount();
threadControler.notifyAll();
}
}
}
}
}
public class Thread2 extends Thread {
ThreadController threadControler;
int sequence;
public Thread2(ThreadController threadControler, int sequence) {
this.threadControler = threadControler;
this.sequence = sequence;
}
@Override
public void run() {
while (true) {
synchronized (threadControler) {
if (threadControler.getCount() != sequence) {
/*
* System.out.println("In thred --- Thread2 : Count is " +
* threadControler.getCount() + ", Sequence is " + sequence);
*/
try {
threadControler.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else if (threadControler.getCount() == sequence) {
System.out.println(
"Print :: Thread2, Count is " + threadControler.getCount() + ", Sequence is " + sequence);
threadControler.incrementCount();
threadControler.notifyAll();
}
}
}
}
}
public class Thread3 extends Thread {
ThreadController threadControler;
int sequence;
public Thread3(ThreadController threadControler, int sequence) {
this.threadControler = threadControler;
this.sequence = sequence;
}
@Override
public void run() {
while (true) {
synchronized (threadControler) {
if (threadControler.getCount() != sequence) {
/*
* System.out.println("In thred --- Thread3 : Count is " +
* threadControler.getCount() + ", Sequence is " + sequence);
*/
try {
threadControler.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else if (threadControler.getCount() == sequence) {
System.out.println(
"Print :: Thread3, Count is " + threadControler.getCount() + ", Sequence is " + sequence);
threadControler.incrementCount();
threadControler.notifyAll();
}
}
}
}
}
public class ThreadController {
private volatile int count = 1;
public int getCount() {
return count;
}
public void incrementCount() {
count++;
}
}
Now test the above code.
public class ThreadSequenceTest {
public static void main(String[] args) {
// In this code we can change sequence number. So we can get the output in same
// sequence. as in below code i want to print t2 than t1 then t3
ThreadController threadControler = new ThreadController();
Thread1 t1 = new Thread1(threadControler, 2);
Thread2 t2 = new Thread2(threadControler, 1);
Thread3 t3 = new Thread3(threadControler, 3);
t1.start();
t2.start();
t3.start();
}
}
Output
Print :: Thread2, Count is 1, Sequence is 1
Print :: Thread1, Count is 2, Sequence is 2
Print :: Thread3, Count is 3, Sequence is 3
