Blocco di thread

[peruzzo]

// An example of deadlock.
class A {
  synchronized void foo(B b) {
    String name = Thread.currentThread().getName();

    System.out.println(name + " entered A.foo");

    try {
      Thread.sleep(1000);
    } catch(Exception e) {
      System.out.println("A Interrupted");
    }

    System.out.println(name + " trying to call B.last()");
    b.last();
  }

  synchronized void last() {
    System.out.println("Inside A.last");
  }
}

class B {
  synchronized void bar(A a) {
    String name = Thread.currentThread().getName();
    System.out.println(name + " entered B.bar");

    try {
      Thread.sleep(1000);
    } catch(Exception e) {
      System.out.println("B Interrupted");
    }

    System.out.println(name + " trying to call A.last()");
    a.last();
  }

  synchronized void last() {
    System.out.println("Inside A.last");
  }
}

class Deadlock implements Runnable {
  A a = new A();
  B b = new B();

  Deadlock() {
    Thread.currentThread().setName("MainThread");
    Thread t = new Thread(this, "RacingThread");
    t.start();

    a.foo(b); // get lock on a in this thread.
    System.out.println("Back in main thread");
  }

  public void run() {
    b.bar(a); // get lock on b in other thread.
    System.out.println("Back in other thread");
  }

  public static void main(String args[]) {
    new Deadlock();
  }
}

Perché se correggo il codice in questo modo:

Deadlock() {
    Thread.currentThread().setName("MainThread");
    Thread m = new Thread(this, "prova");
    m.start();
    Thread t = new Thread(this, "RacingThread");
    t.start();
    a.foo(b); // get lock on a in this thread.
    System.out.println("Back in main thread");
  }

non ottengo 3 thread?

[Dr_House]

Dovresti avere con quella modifica due thread che entrano in visita partendo da B ed uno che entra da A fino a B

Invece che output ti dà?

[peruzzo]

MainThread entered A.foo
prova entered B.bar
MainThread trying to call B.last()
prova trying to call A.last()