laurens.vanhels@telenet.be wrote:
Got a weird CME when doing Map.puts or Map.gets on a private
HashMap
which gets accessed by a SINGLE thread. I also never extract
iterators from the Map.. I only do put() and get().. yet sometimes
I
get ConcurrentModificationException. Toggling the Map between
Hashtable, HashMap or WeakHashMap implementations makes no
difference whatsoever. Black magic, or am I being dense?
Meaning no insult, I suspect the latter.
You say you "never extract iterators," but I bet you do without
realizing it. Note that the `for (Thing t : things)' loop is really
just shorthand for
for (Iterator<Thing> it = things.iterator(); it.hasNext(); ) {
Thing t = it.next();
...
}
so you may be using Iterators even if the string "Iterator" never
shows up in your source code.
From your description, I suspect `things' is either the keySet()
or entrySet() of the Map. If the "..." code executes put() on the
Map (or modifies the Map in any other way), the Iterator will
throw[*]
ConcurrentModificationException at the next hasNext() call.
[*] "Will very probably throw," really. See the Javadoc.
In a single thread, the behavior should be deterministic.