jdk1.8 concurrenthashmap

ConcurrentHashMap is a thread-safe implementation of Map interface that allows concurrent access to the map from multiple threads without any data inconsistency or race condition. It was introduced in Java 5 and has been improved in Java 6 and Java 7.

Some of the key features of ConcurrentHashMap are:
- It is highly concurrent and supports high throughput.
- It allows multiple threads to read and write the map concurrently without any blocking.
- It provides better performance than Hashtable and synchronizedMap.
- It supports high concurrency level with a tunable concurrency level that can be set during initialization.
- It provides various methods for bulk operations such as putAll, clear, and replaceAll.
- It supports atomic operations such as putIfAbsent, remove, and replace.

In JDK 1.8, ConcurrentHashMap has been further improved with the addition of new methods and enhancements such as:
- forEach() method: This method allows you to iterate over the key-value pairs in the map and perform an action on each of them.
- compute() and computeIfAbsent() methods: These methods allow you to update the value of an existing key or add a new key-value pair to the map with a computed value.
- merge() method: This method allows you to merge the values of two keys in the map using a specified function.
- Improved scalability: The internal data structure and algorithms of ConcurrentHashMap have been improved to support better scalability and reduce contention among threads.

Overall, ConcurrentHashMap is a highly efficient and scalable implementation of Map interface that is well-suited for concurrent applications with high throughput and low contention.