different behaviors of java.lang.Object.wait()

I was trying to use java.lang.Object.wait() method and have written 3 different sample codes wherein I am getting different behavior of wait() method.

sample 1)

class Main {
    public static void main(String[] args) throws InterruptedException {
        ThreadB b = new ThreadB();
        b.start();
        Thread.sleep(10000);
        synchronized (b) {
            System.out.println("main thread trying to call wait() method"); //--> 3
            b.wait();
            System.out.println("main thread got notification"); 
            System.out.println(b.total); 
        }
    }
}

class ThreadB extends Thread {
    int total = 0;
    public void run() {
        synchronized (this) {
            System.out.println("child thread starts calculation");  //--> 1
            for (int i=0; i<=100; i++) {
                total = total + i;
            }
            System.out.println("child thread trying to give notification"); //--> 2 
            this.notify();
        }
    }
}

sample 2)

public class Main{
public static void main (String[] args) throws InterruptedException {
    Thread t = new Thread();    
    t.start();
    System.out.println("X"); //--> 1
    synchronized(t) { 
    System.out.println("starting to wait"); //--> 2
    t.wait(10000);
    System.out.println("waiting on t"); //--> 3
    }
    System.out.println("Y"); //--> 4
   }
}

sample 3)

public class Main{
public static void main (String[] args) throws InterruptedException {
     Thread t = new Thread() {public void run() 
                     {System.out.println("I am the second thread.");}};
     t.start();
     System.out.println("X"); //--> 1
     synchronized(t) { 
         Thread.sleep(4000);
         System.out.println("starting to wait"); //--> 2
         t.wait(10000);
         System.out.println("waiting on t"); //--> 3
     }
     System.out.println("Y"); //--> 4
  }
}

In sample 1)

main thread goes in waiting state forever as it has called b.wait() method and there is no thread to provide notify() or notifyAll() on object b. There was child thread that has already been terminated before main thread called b.wait() method. This output is what I expected.

In sample 2)

main thread goes in waiting state for 10 seconds (t.wait(10000);) after printing
X
starting to wait
after 10 seconds main thread executes
waiting on t
Y
This is also my expected output.

In sample 3)

main thread is NOT going in waiting state (t.wait(10000);) even though it is sure that child thread would have been terminated by the time main thread called t.wait(10000); So why it didn't wait ? and straightaway executed
starting to wait
waiting on t
Y
This is NOT my expected output.