ConcurrentMap < K , V > function ( ) { return JdkVersion . getJdkVersion ( ) . isUnsafeSupported ( ) ? new ConcurrentHashMapV8 < K , V > ( ) : new ConcurrentHashMap < K , V > ( ) ; }
creates a new , empty map with a default initial capacity 16 , load factor 0.75 and concurrencylevel 16 . on oracle jdk , the factory method will return an instance of concurrenthashmapv8 that is supposed to be available in jdk 8 and provides better performance and memory characteristics than concurrenthashmap implementation from jdk 7 or earlier . on non-oracle jdk , the factory instantiates the standard concurrenthashmap from jdk . concode_field_sep Class<?> LTQ_CLASS concode_elem_sep int DEFAULT_CONCURENCY_LEVEL concode_field_sep BlockingQueue<E> createLinkedTransferQueue concode_elem_sep Class<?> getAndVerify concode_elem_sep int ceilingNextPowerOfTwo