@Override
            @Nullable
            protected V execute(@Nullable Reference<K, V> ref, @Nullable Entry<K, V> entry, @Nullable Entries<V> entries) {
                if (entry != null) {
                    V oldValue = entry.getValue();
                    if (overwriteExisting) {
                        entry.setValue(value);
                    }
                    return oldValue;
                }
                Assert.state(entries != null, "No entries segment");
                entries.add(value);
                return null;
            }
Return a {link Reference} to the {link Entry} for the specified {@code key},
or {@code null} if not found.

@param key         the key (can be {@code null})
@param restructure types of restructure allowed during this call
@return the reference, or {@code null} if not found
analyzer/src/main/java/nl/basjes/parse/useragent/utils/springframework/util/ConcurrentReferenceHashMap.java