Multiple instantiations of the same object

Question

Can someone please explain to me the difference of these two circumstances upon the JVM:
1) I declare an object outside the loop and instantiate a new object on each iteration of the loop
Object obj = null;
for (int i = 0; i < 6; i++) {
    obj = new Object();
}2) I declare and instantiate the object inside the loop only
for (int i = 0; i < 6; i++) {
    Object obj = new Object();
}I assume in the first example that I am reserving memory space and overwriting it on each iteration, whereas in the second example I am reserving and consuming a new memory space on each iteration.
If that assumption is correct, which is the more efficient? Wouldn't option 1 be easier on garbage collection?

Answer 1

I compiled both cases using Sun javac (1.4.1) and used javap to view the compiled code. It looks the same to me. Here's the compiled code (for the loop) for the first case   2 iconst_0
   3 istore_2
   4 goto 18
   7 new #2 <Class java.lang.Object>
  10 dup
  11 invokespecial #1 <Method java.lang.Object()>
  14 astore_1
  15 iinc 2 1
  18 iload_2
  19 bipush 6
  21 if_icmplt 7
  24 returnHere's the compiled code the second case   0 iconst_0
   1 istore_1
   2 goto 16
   5 new #2 <Class java.lang.Object>
   8 dup
   9 invokespecial #1 <Method java.lang.Object()>
  12 astore_2
  13 iinc 1 1
  16 iload_1
  17 bipush 6
  19 if_icmplt 5
  22 return