One easy way to see if there's a difference is to examine the bytecodes.
The first version compiles to:
public static void f();
Code:
0: bipush 100
2: istore_0
3: iconst_0
4: istore_1
5: goto 26
8: iconst_0
9: istore_2
10: goto 18
13: iconst_3
14: istore_3
15: iinc 2, 1
18: iload_2
19: iload_0
20: if_icmplt 13
23: iinc 1, 1
26: iload_1
27: iload_0
28: if_icmplt 8
31: return
whereas the second compiles to:
public static void g();
Code:
0: bipush 100
2: istore_3
3: iconst_0
4: istore_0
5: goto 26
8: iconst_0
9: istore_1
10: goto 18
13: iconst_3
14: istore_2
15: iinc 1, 1
18: iload_1
19: iload_3
20: if_icmplt 13
23: iinc 0, 1
26: iload_0
27: iload_3
28: if_icmplt 8
31: return
If you compare them closely, you'll see that they are essentially identical.
Stylistically, I think it's preferable to declare variables as close as possible to their first use. With this in mind, I'd choose the first version over the second.