Hi Vitaly, I can buy that argument. It wasn't hard for me to recognize it when I saw it in real world.
But apparently whoever asked me about it couldn't wrap his head around it to understand why... Maybe it's a case for a Pitfalls book instead of for JavaDocs. Thanks, Kris On Friday, July 17, 2015, Vitaly Davidovich <vita...@gmail.com <javascript:_e(%7B%7D,'cvml','vita...@gmail.com');>> wrote: > IMHO, this doesn't warrant any special wording -- if someone hits this, I > think it's fairly evident what the issue is. You can get the same problem > with adding an ArrayList to itself and calling hashCode(). > > On Fri, Jul 17, 2015 at 2:45 PM, Krystal Mok <rednaxel...@gmail.com> > wrote: > >> Hi everyone, >> >> I'm sure somebody has seen this stack overflow before. My question is: is >> it expected (which should be documented to warn people not to do this), or >> is it considered a bug (which should be fixed)? >> >> Example: >> https://gist.github.com/rednaxelafx/930f8979473185cfc0a0 >> >> import java.util.*; >> >> public class HashMapStackOverflow { >> public static void main(String[] args) throws Exception { >> HashMap<String, Object> map = new HashMap<>(); >> map.put("self", map); >> System.out.println(map.hashCode()); >> } >> } >> >> $ ~/sdk/jdk1.8.0/Contents/Home/bin/java HashMapStackOverflow >> Exception in thread "main" java.lang.StackOverflowError >> at java.util.AbstractMap.hashCode(AbstractMap.java:505) >> at java.util.Objects.hashCode(Objects.java:98) >> at java.util.HashMap$Node.hashCode(HashMap.java:296) >> at java.util.AbstractMap.hashCode(AbstractMap.java:507) >> at java.util.Objects.hashCode(Objects.java:98) >> at java.util.HashMap$Node.hashCode(HashMap.java:296) >> at java.util.AbstractMap.hashCode(AbstractMap.java:507) >> at java.util.Objects.hashCode(Objects.java:98) >> at java.util.HashMap$Node.hashCode(HashMap.java:296) >> at java.util.AbstractMap.hashCode(AbstractMap.java:507) >> ... >> >> This will cause a stack overflow because HashMap.hashCode() is inherited >> from AbstractMap, which sums the hash code of each entry, while one of the >> entries is itself so it goes recursive. >> >> Thanks, >> Kris >> > >
