HashSet ordering

[Paul Stat]

I've just reached the end of chapter 7 K&B Collections & Generics, and I thought I'd practice coding some of the Collections mentioned.

It says HashSet: "an unsorted, unordered Set", if that's the case why does the following code

HashSet<Integer> s1 = new HashSet<Integer>();
s1.add(3);
s1.add(5);
s1.add(1);
s1.add(4);
s1.add(2);
s1.add(2);  // Duplicates not allowed won't be added to Set
Iterator i4 = s1.iterator();
while(i4.hasNext()) {
    System.out.println(i4.next());
}

Produce this seemingly ordered output

1
2
3
4
5

[Henry Wong]

Try it with different numbers -- or with strings.

Henry

[James Tharakan]

Overriden the hashcode and equals method.

[Henry Wong]

BTW, "unordered" does not mean that the order is random. It does not mean that the order changes with each run. In fact, you can't infer anything here. In fact, as you have seen, for certain cases, on certain platforms, it can actually be seemingly ordered.

James Tharakan wrote:Overriden the hashcode and equals method.

While the integer class does override those methods, I don't see how that fact has any relevance to this question.

Henry

[Paul Stat]

Henry Wong wrote:
Try it with different numbers -- or with strings.

Henry

Ok then, so what determines the "order" in which it's elements are printed?

[James Tharakan]

Henry Wong wrote:

While the integer class does override those methods, I don't see how that fact has any relevance to this question.

Henry

Yeah..... i am sorry .....

[Paul Stat]

Henry Wong wrote:
BTW, "unordered" does not mean that the order is random. It does not mean that the order changes with each run. In fact, you can't infer anything here. In fact, as you have seen, for certain cases, on certain platforms, it can actually be seemingly ordered.

Hmm ok, thanks!

[Vijay Raj]

Henry, what does 'unordered' mean then? Does it mean that the order is not predictable?

Vijay.

[Ruben Soto]

I think that what Henry means (and what the documentation means by "unordered") is that you shouldn't rely on any specific order. In this case, probably due to the specific implementation, you are getting an apparently ordered sequence, but you shouldn't rely on that fact as it is not guaranteed.

[akash azal]

hey paul can you explain the question no 14 from chapter 7 of k&s

[Henry Wong]

akash azal wrote:hey paul can you explain the question no 14 from chapter 7 of k&s

If this is a related question, please elaborate. Otherwise, please do not hijack topics.

Henry