Due to internal details of the Iterator returned by IdentityHashMap.entrySet().iterator(), the toArray method in question will contain size() identical object references to a non-functional Map.Entry. Any attempt to use the Entry will throw an Index out of bounds error. The following program should generate no output and exit normally:

import java.util.*;

public class ToArray {
    public static void main(String[] args) {
        Map m = new IdentityHashMap();
        m.put("french", "connection");
        m.put("polish", "sausage");
        Object[] mArray = m.entrySet().toArray();
        if (mArray[0] == mArray[1])
            System.out.println("Broken");

        // Calls toString on mArray[0], which throws IndexOutOfBoundsException
        mArray[0].toString();
    }
}

Instead it prints "broken" and throws an IndexOutOfBoundsException.