/guava/guava/src/com/google/common/collect/Ordering.java
Integer uid = uids.get ( obj ) ;
@VisibleForTesting static class ArbitraryOrdering extends Ordering<@Nullable Object> { private final AtomicInteger counter = new AtomicInteger(0); private final ConcurrentMap<Object, Integer> uids = Platform.tryWeakKeys(new MapMaker()).makeMap(); private Integer getUid(Object obj) { <extra_id_0> if (uid == null) { uid = counter.getAndIncrement(); Integer alreadySet = uids.putIfAbsent(obj, uid); if (alreadySet != null) { uid = alreadySet; }