Difference Betwixt Concurrenthashmap, Hashtable Together With Synchronized Map Inwards Java

ConcurrentHashMap vs Hashtable vs Synchronized Map
Though all 3 collection classes are thread-safe as well as tin endure used inward multi-threaded, concurrent Java application, at that topographic point is a pregnant deviation betwixt them, which arise from the fact that how they accomplish their thread-safety. Hashtable is a legacy cast from JDK 1.1 itself, which uses synchronized methods to accomplish thread-safety. All methods of Hashtable are synchronized which makes them quite boring due to disputation if a release of thread increases. Synchronized Map is every bit good non rattling dissimilar than Hashtable as well as provides similar surgical operation inward concurrent Java programs. The alone deviation betwixt Hashtable as well as Synchronized Map is that after is non a legacy as well as you lot tin roll whatever Map to create it's synchronized version yesteryear using Collections.synchronizedMap() method.


On the other hand, ConcurrentHashMap is particularly designed for concurrent role i.e. to a greater extent than than ane thread. By default it simultaneously allows xvi threads to read as well as write from Map without whatever external synchronization. It is every bit good rattling scalable because of stripped locking technique used inward the internal implementation of ConcurrentHashMap class. Unlike Hashtable as well as Synchronized Map, it never locks whole Map, instead, it divides the map into segments as well as locking is done on those. Though it performs amend if a release of reader threads are greater than the release of author threads.

To endure frank, Collections classes are the catch of Java API though I experience using them judiciously is an art. It's my personal experience where I accept improved the surgical operation of Java application yesteryear using ArrayList where legacy codes were unnecessarily using Vector etc. Prior Java 5, One of the major drawback of Java Collection framework was a lack of scalability.


In multi-threaded Java application synchronized collection classes similar Hashtable as well as Vector chop-chop becomes the bottleneck; to address scalability JDK 1.5 introduces only about expert concurrent collections which are highly efficient for high volume, depression latency organisation electronic trading systems In full general those are the backbone for Concurrent fast access to stored data.


In this tutorial, nosotros volition await on ConcurrentHashMap, Hashtable, HashMap as well as synchronized Map as well as come across the deviation betwixt ConcurrentHashMap as well as Hashtable as well as synchronized Map inward Java. We accept already discussed only about key difference betwixt HashMap as well as Hashtable inward Java in this weblog as well as those volition every bit good help you lot to reply this query during interviews.

Why withdraw ConcurrentHashMap as well as CopyOnWriteArrayList

The synchronized collections classes, Hashtable, as well as Vector, as well as the synchronized wrapper classes, Collections.synchronizedMap() as well as Collections.synchronizedList(), render a basic conditionally thread-safe implementation of Map as well as List. However, several factors brand them unsuitable for role inward highly concurrent applications, for example, their unmarried collection-wide lock is an impediment to scalability as well as it frequently becomes necessary to lock a collection for a considerable fourth dimension during iteration to foreclose ConcurrentModificationException.

ConcurrentHashMap as well as CopyOnWriteArrayList implementations render much higher concurrency spell preserving thread safety, alongside only about tyke compromises inward their promises to callers. ConcurrentHashMap as well as CopyOnWriteArrayList are non necessarily useful everywhere you lot mightiness role HashMap or ArrayList, but are designed to optimize specific mutual situations. Many concurrent applications volition practice goodness from their use. 

Difference betwixt ConcurrentHashMap as well as Hashtable

So what is the deviation betwixt Hashtable as well as ConcurrentHashMap, both tin endure used inward the multithreaded environs but ane time the size of Hashtable becomes considerable large surgical operation degrade because for iteration it has to endure locked for a longer duration.

Since ConcurrentHashMap introduced the concept of segmentation, how large it becomes alone certainly business office of it teach locked to render thread security thus many other readers tin notwithstanding access map without waiting for iteration to complete. 

In Summary, ConcurrentHashMap alone locked certainly component of Map spell Hashtable locks amount map spell doing iteration. This volition endure clearer yesteryear looking at this diagram which explains the internal working of ConcurrentHashMap inward Java.

The deviation betwixt ConcurrentHashMap as well as Collections.synchronizedMap

ConcurrentHashMap is designed for concurrency as well as improve surgical operation spell HashMap which is non-synchronized yesteryear nature tin endure synchronized yesteryear applying a wrapper using synchronized Map. Here are only about of the mutual differences betwixt ConcurrentHashMap as well as synchronized map inward Java

ConcurrentHashMap does non allow aught keys or aught values spell synchronized HashMap allows ane aught key.

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