Time to create object dependent on depth of class hierachy?

Question

hi,
running the code below seems to show that instantiating two classes that have the same members but have different inheritence trees can effect the object creation time.
(A2 is taking longer on my tests on Windows, HP/UX and Linux, and the same amount of time under Solaris)
is the test broken? if not, then can anyone explain why this is the case?
thanks,
asjf
class G {int g;}
class F extends G {int f;}
class E extends F {int e;}
class D extends E {int d;}
class C extends D {int c;}
class B extends C {int b;}
class A1 extends B {int a;}
class A2 {
   int a,b,c,d,e,f,g;
public class GoTest {
   public static void main(String [] arg) {
      long COUNT = 5000000, timer=0;
      while(true) {
         timer = -System.currentTimeMillis();
         for(int i=0; i<COUNT; i++) new A1();
         System.out.print("inheriting="+(timer+System.currentTimeMillis()));
         timer = -System.currentTimeMillis();
         for(int i=0; i<COUNT; i++) new A2();
         System.out.println(", flat="+(timer+System.currentTimeMillis()));
}

Answer 1

The test is broken. I've run the program on Windows,
and without changes it behaves as you describe. But
swap the test loops and suddenly the flat objects are
allocated faster. After some experiments, my guess
would be that the first test loop, maybe even the
first allocation determines which runs faster. Looks
like some optimization of the VM kicks in, depending
on what happens first. I don't have the server VM
installed, but the results might clarify things a bit.ah good point about swapping the tests - i get the same results..
running 1.4.2 java with -server makes both loops take the same time. I don't get why there is such a long delay on the second object creation loop though..
so that only leaves the question why this slightly altered bit of code has a limp on the client vm (like Morin suggested it depends on which class goes first)
thanks,
asjf
import java.util.Random;
class A {}
class B {}
public class GoTest2 {
   public static void main(String [] arg) {
      long COUNT = 5000000, timer=0;
      Random r = new Random();
      while(true) {  
           if(r.nextBoolean()) {
              timer = -System.currentTimeMillis();
              for(int i=0; i<COUNT; i++) new A();
              System.out.println("a "+(timer+System.currentTimeMillis()));
           } else {
              timer = -System.currentTimeMillis();
              for(int i=0; i<COUNT; i++) new B();
              System.out.println("b "+(timer+System.currentTimeMillis()));
}