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Keys and values can be any types, but all the keys in an associative array must be of the same type, and the same goes for dependent values. Looping through all properties and associated values, and printing them, can be coded as follows:
Lookup, find, or get find the value (if any) that is bound to a given key. The argument to this operation is the key, and the value is returned from the operation. If no value is found, some lookup functions raise an exception, while others return a default value (such as zero, null, or a specific value passed to the constructor).
For unordered access as defined in the java.util.Map interface, the java.util.concurrent.ConcurrentHashMap implements java.util.concurrent.ConcurrentMap. [2] The mechanism is a hash access to a hash table with lists of entries, each entry holding a key, a value, the hash, and a next reference.
A small phone book as a hash table. In computer science, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [3]
Based on this non-growing implementation, a variety of different growing hash tables is given. These implementations allow for concurrent reads, inserts, updates (notably updating values based on the current value at the key) and removals (based upon updating using tombstones). Beyond that, variants on the basis of Intel TSX are provided. The ...
In its basic form, a hash tree stores the hashes of its keys, regarded as strings of bits, in a trie, with the actual keys and (optional) values stored at the trie's "final" nodes. [1] Hash array mapped tries and Ctries are refined versions of this data structure, using particular type of trie implementations. [1]
Collection implementations in pre-JDK 1.2 versions of the Java platform included few data structure classes, but did not contain a collections framework. [4] The standard methods for grouping Java objects were via the array, the Vector, and the Hashtable classes, which unfortunately were not easy to extend, and did not implement a standard member interface.
Computing the hash value of a given key x may be performed in constant time by computing g(x), looking up the second-level function associated with g(x), and applying this function to x. A modified version of this two-level scheme with a larger number of values at the top level can be used to construct a perfect hash function that maps S into a ...