supertype constructor

[preeti khane]

 
Q43.What will be the result of compiling and running the given program?
    Select one correct answer.
  1. class Q43 
  2. { 
  3.    int y=1; 
  4.    Q43() 
  5.    { 
  6.       this(y);
  7.    } 
  8.    Q43(int x) 
  9.    { 
  10.      y=x++ + ++x;
  11.   } 
  12.   public static void main(String [] args) 
  13.   { 
  14.      Q43 t = new Q43(); 
  15.      System.out.println(t.y);
  16.   } 
  17. }
 Program compiles correctly and prints 1 when executed. 
 Program compiles correctly and prints 4 when executed. 
 Compile time error. 
 None of above. 
 

It says compile time error - cannot reference Q43.y until supertype constructor has been called
I am not sure I understand the error... Can someone explain? Does it mean super() has to be called or that a base class should exist for this class

[Praveen Kumar Mathaley]

According to jls, one cannot access instance variables in the calls to super constructors as still they are not intialized( follow the object creation thread flow.)
in the given class the no argument constructor is calling the argument constructor, so still the super constructor has not been called yet at the line this(y) hence the compilation error that cannot reference y before call to supertype constructor.