SCJP - 29 -Given Example

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

Answer:

F is correct. The m2 object’s m1 instance variable is never initialized, so when m5 tries to
use it a NullPointerException is thrown.

A, B, C, D, and E are incorrect based on the above. (Objective 7.3)
==

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 "); }
}