HashSet order and difference with JDK 7 / 8

This is a two part question:

1. Does HashSet implement some hidden ordering mechanic or it just, to quote the documentation:It makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. tells me that the order MIGHT change sometimes in the future and/or depending on memory usage?
2. Why am I getting completely different 'ordering' (dare I say) when I switch between JDKs?

Take this example:

for (int i = 0; i < 1000; i++) {
        Set<String> stringSet = new HashSet<>();
        stringSet.add("qwe");
        stringSet.add("rtz");
        stringSet.add("123");
        stringSet.add("qwea");
        stringSet.add("12334rasefasd");
        stringSet.add("asdxasd");
        stringSet.add("arfskt6734");
        stringSet.add("123121");
        stringSet.add("");
        stringSet.add("qwr");
        stringSet.add("rtzz");
        stringSet.add("1234");
        stringSet.add("qwes");
        stringSet.add("1234rasefasd");
        stringSet.add("asdxasdq");
        stringSet.add("arfskt6743");
        stringSet.add("123121 ");
        stringSet.add(" ");
        System.out.println(stringSet);
    }

will, no matter how many times I run it, produce the following output:

JDK 7: [, , 123, qwea, asdxasdq, qwe, qwr, 123121 , arfskt6743, 1234rasefasd, qwes, rtz, rtzz, 1234, 12334rasefasd, asdxasd, arfskt6734, 123121]

JDK 8: [, , qwes, arfskt6743, asdxasdq, 123121, 123121 , arfskt6734, qwr, 123, 1234, qwea, rtzz, rtz, 12334rasefasd, 1234rasefasd, qwe, asdxasd]

Obviously, the empty string and the whitespace-only-string are leading the way both times, but the rest of it is completely different.