Both collections implements Map and store values as key-value pairs. The key differences between the two are: HashMap is not synchronized in nature but Hashtable is. Another difference is that iterator in the HashMap is fail-safe while the enumerator for the Hashtable isn't fail-safe, If the Hashtable is structurally modified at any time after the ...

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In computing, a hash map (hash table) is an unsorted, unordered version of Map used to implement an associative array, a structure that can map keys to values. A hash map uses a hash function to compute an index into an array of buckets or slots, from which the desired value can be found.The example given below covers most of the common uses of Has...

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We can sort a Map by its keys but here we see how we can sort it by values. Steps to sort Map by Value : 1. Get all entry object of that map into list. 2. Use sort(list,comparator) to sort the entry objects by values. We have to write one Comparator for that. 3. We will get Entry object sorted by values and now we can iterate it to create new sorte...

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Synchronization or Thread Safe: This is the most important difference between two. HashMap is non-synchronized and not thread safe. On the other hand, Hashtable is thread safe and synchronized. If your application do not require any multi-threading task, in other words HashMap is better for non-threading applications. Hashtable should be used in mu...

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Hash table’s offer concurrent access to their entries, with a small caveat, the entire map is locked to perform any sort of operation. While this overhead is ignorable in a web application under normal load, under heavy load it can lead to delayed response times and overtaxing of your server for no good reason because for iteration it has to be loc...

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Both provide thread safe operations of collections of data and used in multithreaded programs to provide both thread safety and performance improvements ConcurrentHashMap will create a HashEntry [] array internally to store the elements passed in from a Map, while Collections.synchronizedMap () will return a Synchronized Map. The main difference be...

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A cache (pronounced as cash) is a place in memory to store some information temporarily, so that it can be retrieved faster, eliminating the necessity to compute the same information over and over again.This saves a lot of computation effort. There are various caching algorithms present and caching itself is a vast subject on its own. LRU cache or ...

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TreeMap class extends AbstractMap and implements NavigableMap interface.  It creates a map stored in a tree structure.  TreeMap is sorted according to natural ordering of keys or by using an implementation of the Comparator interface. The difference between TreeMap and HashMap  A HashMap doesn’t guarantee about the order of retrieval of its element...

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Map is one of the most important data structures in Java. In this post, we will see that how to use different types of maps, such as HashMap, TreeMap, HashTable and LinkedHashMap. 1. Overview Of Map: There are 4 commonly used implementations of Map in Java SE - HashMap, TreeMap, Hashtable and LinkedHashMap. The implementations can be described as f...

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A sorting algorithm is an algorithm that puts elements of a list in a certain order. The most-used orders are numerical order and lexicographical order. To sort a map we will use the two main important features of map i.e. key and value a) Sort by Key HashMap makes absolutely no guarantees about the iteration order. It can (and will) even change co...

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In this article we will see. How we can sort a HashMap by Keys and Values. Sorting by keys is very straight forward. We just need to create a TreeMap from the HashMap. The TreeMap is a Red-Black tree based NavigableMap implementation. The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, ...

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TreeMap in Java :  TreeMap class extends AbstractMap and implements NavigableMap interface. It creates a map stored in a Tree structure. TreeMap is sorted according to natural ordering of keys or by using an implementation of the Comparator interface. To maintain this sorted order, making an object as key in a TreeMap , we need to follow either of ...

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