Are HashMap entries always sorted by key if the key is of type Integer?

Question

I am looking for an implementation that automatically sorts its records by key. I found an implementation TreeMapthat does this correctly. However, in the tests I created, I found that entries in HashMapare sorted by their key, if the key is of type Integer, by default. Can I assume that it HashMapworks (and continues to work) like this, and uses it safely, or should I use it TreeMapfor this purpose?

Answer 1

No, you cannot assume that entries in HashMapare sorted by their key, since that is not the case.

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HashMap<Integer,String> map = new HashMap<> ();
for (int i=0;i<10;i++) {
  map.put (i, Integer.toString (i));
}
for (Integer key : map.keySet ()) {
  System.out.println (key);
}

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HashMap<Integer,String> map = new HashMap<> ();
for (int i=0;i<10;i++) {
  map.put (i*100, Integer.toString (i));
}
for (Integer key : map.keySet ()) {
  System.out.println (key);
}

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