Почему не срабатывает сериализация доступа

class Callme {
  synchronized void call(String msg) {
    System.out.print("[" + msg);
    try {
      Thread.sleep(2000);
    } catch(InterruptedException e) {
      System.out.println("Interrupted");
    }
    System.out.println("]");
  }
}
 
class Caller1 implements Runnable {
  String msg;
  Callme target;
  Thread t;
 
  public Caller1(Callme targ, String s) {
    target = targ;
    msg = s;
    t = new Thread(this);
    t.start();
  }
 
  public void run() {
    target.call(msg);
  }
}
 
class Demo3 {
  public static void main(String args[]) {
    Callme target = new Callme();
    Caller1 ob1 = new Caller1 (target, "Hello");
    Caller1 ob2 = new Caller1 (target, "Synchronized");
   Caller1 ob3 = new Caller1 (target, "World");
 
    // wait for threads to end
    try {
      ob1.t.join();
      ob2.t.join();
      ob3.t.join();
    } catch(InterruptedException e) {
      System.out.println("Interrupted");
    }
  }
}

class Caller implements Runnable {
  String msg;
  Thread t;
 
  public Caller(String s) {
    msg = s;
    t = new Thread(this);
    t.start();
  }
 
  public void run() {
    call(msg);
  }
    
  synchronized void call(String msg) {
    System.out.print("[" + msg);
    try {
      Thread.sleep(2000);
    } catch(InterruptedException e) {
      System.out.println("Interrupted");
    }
    System.out.println("]");
  }
}
 
class Demo {
  public static void main(String args[]) {
    Caller ob1 = new Caller("Hello");
    Caller ob2 = new Caller("Synchronized");
    Caller ob3 = new Caller("World");
 
    try {
      ob1.t.join();
      ob2.t.join();
      ob3.t.join();
    } catch(InterruptedException e) {
      System.out.println("Interrupted");
    }
  }
}

run:
[Hello]
[World]
[Synchronized]

run:
[Hello[World[Synchronized]
]
]