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  1. What will be the output of the program?

     public class Q126 implements Runnable
 {     
     private int x;   
     private int y;    

     public static void main(String [] args)      
     {     
        Q126 that = new Q126();            
        (new Thread(that)).start( ); /* Line 8 */  
        (new Thread(that)).start( ); /* Line 9 */    
 }     
 public synchronized void run( ) /* Line 11 */  
 {    
      for (;;) /* Line 13 */    
      {   
           x++;     
           y++;              
           System.out.println("x = " + x + "y = " + y);         
      }     
   }  
}

    2. A.

    An error at line 11 causes compilation to fail
    B.

    Errors at lines 8 and 9 cause compilation to fail.
    C.

    The program prints pairs of values for x and y that might not always be the same on the same line (for example, "x=2, y=1")
    D.

    The program prints pairs of values for x and y that are always the same on the same line (for example, "x=1, y=1". In addition, each value appears once (for example, "x=1, y=1" followed by "x=2, y=2")

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    Answer : Option D

    Explanation :

    The synchronized code is the key to answering this question. Because x and y are both incremented inside the synchronized method they are always incremented together. Also keep in mind that the two threads share the same reference to the Q126 object.

    Also note that because of the infinite loop at line 13, only one thread ever gets to execute.

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