A DESCRIPTION OF THE PROBLEM :
Introduced by the fix for JDK-4485486 / JDK-6197726, though probably did not work properly before either because these bugs blocked it.

The toArray() / toArray(T[]) methods of the Set returned by IdentityHashMap.entrySet() break the contract of the documentation of this method:
"containing all of the elements in this set"
with emphasis on "elements in this set"

toArray() actually returns different Entry objects, which are not even a valid substitute for the proper Entry objects because:
- They have no relation to the map anymore, calling setValue() has no effect
- They compare the stored key and value using `equals` instead of comparing references

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
import java.util.IdentityHashMap;
import java.util.Map.Entry;
import java.util.Set;

public class MapTest {
    public static void main(String[] args) {
        IdentityHashMap<String, String> identityHashMap = new IdentityHashMap<>();
        final String key = "key";
        final String oldValue = "oldValue";
        final String newValue = "newValue";
        
        identityHashMap.put(key, oldValue);
        Set<Entry<String, String>> entrySet = identityHashMap.entrySet();
        
        @SuppressWarnings("unchecked")
        Entry<String, String> arrayEntry = (Entry<String, String>) entrySet.toArray()[0];
        // Expecting that this changes value in map
        arrayEntry.setValue(newValue);
        // -> !! Did not change value
        System.out.println("Expecting true: " + (identityHashMap.get(key) == newValue));
        
        Entry<String, String> iteratorEntry = entrySet.iterator().next();
        // Expecting that this changes value in map
        iteratorEntry.setValue(newValue);
        // -> Changed value
        System.out.println("Expecting true: " + (identityHashMap.get(key) == newValue));
        
        /*
         * Set.toArray() contract is violated because here it does not return
         * "all of the elements in this set", it actually returns different elements
         */
    }
}



FREQUENCY : always