Explanation needed for a question

[Pad Ven]

Hi all,
Can someone explain why I get "STP as output from this program even though the println statements show that my understanding that "default" is the last value assigned is correct, in the program below:

public class OuterTest {

String id ;

OuterTest ( ) {
this . id = " Default " ;
System.out.println ("No-args constructor called");
System.out.println ("Outertest.this.id : " + this.id);
}

OuterTest ( String id ) {
this . id = id ;
System.out.println ("Single-args constructor called");
System.out.println ("Outertest.this.id : " + this.id);
}

class InnerTest extends OuterTest {

void doSomething ( ) {
System . out . println ( OuterTest . this . id ) ;
}
};

public static void main ( String args [ ] ) {
OuterTest outer = new OuterTest ( " STP " ) ;
InnerTest inner = outer . new InnerTest ( ) ;
inner . doSomething ( ) ;
}
};

The output I got was



Single-args constructor called
Outertest.this.id : STP
No-args constructor called
Outertest.this.id : Default
STP



How come then when [B} doSomething [/B} is callef, the value is "STP"

Regards,
Padmanabhan

[Ganesh Pujar]

Let me try to explae you.

public class OuterTest {
 
String id ;//Line 1
 
OuterTest ( ) {
this . id = " Default " ;
System.out.println ("No-args constructor called");
System.out.println ("Outertest.this.id : " + this.id);
}
 
OuterTest ( String id ) {
this . id = id ;
System.out.println ("Single-args constructor called");
System.out.println ("Outertest.this.id : " + this.id);
}
 
class InnerTest extends OuterTest {
 
void doSomething ( ) {//Line 2
System . out . println ( OuterTest . this . id ) ;//Line 3
}
};
 
public static void main ( String args [ ] ) {
OuterTest outer = new OuterTest ( " STP " ) ;
InnerTest inner = outer . new InnerTest ( ) ;
inner . doSomething ( ) ;//Line 4
}
};

Line 4 will call function on Line 2, and the Line 3 will be excuted as follows
OuterTest . this . id whcih can be looked as
OuterTest-->CurrentlyExceutingThread-->its id
So which makes it as
OuterTest.Outer.id which is STP


To get the default as output in the last line, you have to change the Line 1 to
static String id ;

Ranchers
Correct me if i'm wrong.

[Deepak Chandrashekar Avanna]

void doSomething ( ) {
System . out . println ( id ) ;
}


Note that I have changed the method to print just id. Now you will get your desired output of Default. This has to do with inner class inheritance.


In your previous code, you were explicitly printing the OuterClass.this.id and hence it was printing the STP.

[Saurabh Vyas]

Hi Ranchers,

   
OuterTest outer = new OuterTest ( " STP " ) ; // Line 1
InnerTest inner = outer . new InnerTest ( ) ;  // Line 2

In Line 1 we are creating an object of OuterTest with one argument. Thus id for that object will be set as �STP�.

Now in Line2 we use the above created object to create an object of InnerTest class.
So for InnerTest�s object, id will hold the value �Default�.

    
void doSomething ( ) {
System . out . println ( OuterTest . this . id ) ;
}

Now in doSomething method we are calling OuterTest.this.id which means we want the value of id for the Parent class of the current object. Ie id of the object through which the object of InnerTest was created. Thus this means that we are trying to fetch the value of id for the object called �outer�. Thus it prints �STP�.

If we want to print �Default� than just modify doSomthing() method as follows

    
void doSomething ( ) {
System . out . println ( this . id ) ;
}

Now the last line of o/p will be �Default�. This is b�cos value of id is set as �Default� by the constructor of InnerTest which calls its parents� no argument constructor,