initialization

[shilpa Reddy]

Given:
class Mixer {
Mixer() { }
Mixer(Mixer m) { m1 = m; }
Mixer m1;
public static void main(String[] args) {
Mixer m2 = new Mixer();
Mixer m3 = new Mixer(m2); m3.go();
Mixer m4 = m3.m1; m4.go();
Mixer m5 = m2.m1; m5.go();
}
void go() { System.out.print("hi "); }
}
What is the result?
A. hi
B. hi hi
C. hi hi hi
D. Compilation fails
E. hi, followed by an exception
F. hi hi, followed by an exception

In the above question is Mixer m1 a static variable. if not then how can Mixer m4 = m3.m1; m4.go(); this piece of code go thru.kindly help

[wise owen]

hi hi, followed by an exception

m1 is an instance variable. m1 is NULL in m2 referenced object.
[ August 01, 2006: Message edited by: wise owen ]

[Naseem Khan]

In the above question is Mixer m1 a static variable. if not then how can Mixer m4 = m3.m1; m4.go(); this piece of code go thru.kindly help

m1 is not an static variable. m3.m1 means m3 HAS-A variable m1. This m1 is pointing to m2 instance.

Mixer m2 = new Mixer();     // its m1 is null
Mixer m3 = new Mixer(m2);   // its m1 is pointing to m2
Mixer m4 = m3.m1;           // same as Mixer m4=m2;
m4.go();                    // same as m2.go();
Mixer m5 = m2.m1;           // same as m5=null as m1 instance variable of  
                               m2 object is null.
m5.go();                    // NullPointerException here.

Naseem

[shilpa Reddy]

how can a static methoed access a non static variable

[Naseem Khan]

That why we are accessing m1 by an object.

m3.m1

Naseem
[ August 01, 2006: Message edited by: Naseem Khan ]

[shilpa Reddy]

thats the question in k&b. i don get you clear

[Naseem Khan]

What I am saying is if you access m1 without any associated object like below, then its not possible and you will get compilation error saying non-static things can't be accessed by its simple name in a static context.

But your are not accessing m1 by its simple name rather you are accessing it by an object.

Following code will not compile

Mixer m4 = m1;      // compilation error here.
// m4.go();
Mixer m5 = m1;      // compilation error here.
// m5.go();

Naseem
[ August 01, 2006: Message edited by: Naseem Khan ]