Why entryset in HashMap calls entryset0?

Question

Why entryset in HashMap calls entryset0 instead of directly writing

Set <Map.Entry <K, V >> es = entrySet; 
! return es = null es: (entrySet = new EntrySet ());

In the writeObject method directly calls entrySet0, is that because of the reason that the entrySet method can be overridden?

score 0 · Accepted Answer · answered Aug 16 '14 at 03:24

0

Your explanation is the most plausible. This is to insulate the implementation of HashMap from the effects of someone overriding the entrySet() method in a subtype.

The only other explanation I can think of is that this is left over from some older version of the class, and I wouldn't expect that the Java developers would have let that happen here. (This is code has lots of eyeballs on it ...)

Either way, it probably makes no difference to performance. The JIT compiler is likely to inline the call ... except in the case where there is a subclass of HashMap that does override entrySet().

answered Aug 16 '14 at 03:24

Stephen C

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If it were just about overriding, they could mark it as final. – yshavit Aug 16 '14 at 04:07
Ermm ... that would *prevent* overriding. My / our guess is that they want to *allow* overriding of that method, but in a way that doesn't break the internals of `HashMap`. – Stephen C Aug 16 '14 at 04:13
Eh... I'm going to see if it is overwritten by other classes! – sangjian Aug 16 '14 at 04:21
I found it! In `ProcessEnvironment` class,the `entrySet` method is overwritten `public Set> entrySet() { return new CheckedEntrySet(super.entrySet()); }` – sangjian Aug 16 '14 at 04:32
Overridden ... not overwritten. – Stephen C Aug 16 '14 at 04:36

Why entryset in HashMap calls entryset0?

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