public final V get(K key) {
        final int hash = System.identityHashCode(key);
        final int bucket = hash & indexMask;

        for (Entry<K, V> entry = buckets[bucket]; entry != null; entry = entry.next) {
            if (key == entry.key) {
                return (V) entry.value;
            }
        }

        return null;
    }
for concurrent IdentityHashMap

@author wenshao[szujobs@hotmail.com]
src/main/java/com/alibaba/fastjson/util/IdentityHashMap.java