Help with Understanding the Output

[Dhruv Arya]

class X 
{
	Y b = new Y();
        	X() 
	{ 
		System.out.print("X"); 
	}
}

class Y 
{
        	Y() 
	{ 
		System.out.print("Y"); 
	}
}

public class Z extends X 
{
        	Y y = new Y();

        	Z() 
	{ 
		System.out.print("Z"); 
	}

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

The output comes out to be YXYZ Can someone explain how is this ?

[Henry Wong]

The output comes out to be YXYZ Can someone explain how is this ?

The instantiation order for objects are...

1. All instance variables (that are compile time constants) are done first.... Actually, this is done at compile time, but this is first nonetheless.
2. The super() portion of the constructor is called.
3. All instance variables are initialization, and instance initializers are called, in the order that they are encountered in the source.
4. The rest of the constructor is called.


So... if you apply this, you should get YXYZ.

Henry

[Dhruv Arya]

I didnt get the third point. Does it also initialize the Y class object declared in class X and that happens after the class X constructor has run

[Henry Wong]

Dhruv Arya wrote:I didnt get the third point. Does it also initialize the Y class object declared in class X and that happens after the class X constructor has run

The y instance variable of X, will be instantiated, after the super() part of the X constructor, but before the rest of the constuctor.

Henry

[Valentin Ivanov]

Henry Wong wrote:The y instance variable of X, will be instantiated, after the super() part of the X constructor, but before the rest of the constuctor.Henry

So shouldn't the answer be YYXZ?

[Henry Wong]

Valentin Ivanov wrote:So shouldn't the answer be YYXZ?

instantiate Z
---> super() of Z, ie. instantiate X portion
--------> super() of X, ie. Object portion
--------> variables of X, prints ................................. Y
--------> rest of X constructor, prints ....................... X
---> variables of Z, prints ....................................... Y
---> rest of Z constructor, prints ............................. Z


Henry

[Dhruv Arya]

Thanks alot Henry I get it now Thank You