5,879
2019-05-18 19:03:16
First example: No multiple threads. Both execute in single (existing) thread. No thread creation.
R1 r1 = new R1();
R2 r2 = new R2();
r1 and r2 are just two different objects of classes that implement the Runnable interface and thus implement the run() method. When you call r1.run() you are executing it in the current thread.
Second example: Two separate threads.
Thread t1 = new Thread(r1);
Thread t2 = new Thread(r2);
t1 and t2 are objects of the class Thread. When you call t1.start(), it starts a new thread and calls the run() method of r1 internally to execute it within that new thread.
Couuld I consider that before we call Thread#start() ,nothing really relative to os thread happens? It is only a java object.
That's correct according to the documentation. Check the thread object initialization code, which conforms to the documentation. Also in the source code, it's the
start(), which is calling a natvie method, which must be making the os thread related things happen.Thread constructor docs is here. Thread object initialization source is here.
start()method source is here.