Though all three collection classes are thread-safe and can be used in multi-threaded, concurrent Java application, there is significant difference between them, which arise from the fact that how they achieve their thread-safety. Hashtable is a legacy class from JDK 1.1 itself, which uses synchronized methods to achieve thread-safety. All methods of Hashtable are synchronized which makes them quite slow due to contention if number of thread increases. Synchronized Map is also not very different than Hashtable and provides similar performance in concurrent Java programs. Only difference between Hashtable and Synchronized Map is that later is not a legacy and you can wrap any Map to create it's synchronized version by using Collections.synchronizedMap() method. On the other hand, ConcurrentHashMap is especially designed for concurrent use i.e. more than one thread. By default it simultaneously allows 16 threads to read and write from Map without any external synchronization. It is also very scalable because of stripped locking technique used in internal implementation of ConcurrentHashMap class. Unlike Hashtable and Synchronized Map, it never locks wholeMap, instead it divides the map in segments and locking is done on those. Though it perform better if number of reader threads is greater than number of writer threads.
Collections classes are heart of Java API we can improved performance of Java application by using ArrayList where legacy codes were unnecessarily using Vector etc. Prior Java 5, One of the major drawback of Java Collection framework was lack of scalability. In multi-threaded Java application synchronized collection classes like Hashtable and Vector quickly becomes bottleneck; to address scalability JDK 1.5 introduces some good concurrent collections which is highly efficient for high volume, low latency system electronic trading systems In general those are backbone for Concurrent fast access of stored data. In this tutorial we will look on ConcurrentHashMap, Hashtable,HashMap and synchronized Map and see difference between ConcurrentHashMap and Hashtable and synchronized Map in Java.
Collections classes are heart of Java API we can improved performance of Java application by using ArrayList where legacy codes were unnecessarily using Vector etc. Prior Java 5, One of the major drawback of Java Collection framework was lack of scalability. In multi-threaded Java application synchronized collection classes like Hashtable and Vector quickly becomes bottleneck; to address scalability JDK 1.5 introduces some good concurrent collections which is highly efficient for high volume, low latency system electronic trading systems In general those are backbone for Concurrent fast access of stored data. In this tutorial we will look on ConcurrentHashMap, Hashtable,HashMap and synchronized Map and see difference between ConcurrentHashMap and Hashtable and synchronized Map in Java.
