StackOverflowError on HashMap.hashCode() due to self reference

[Krystal Mok]

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