Java Share an insight from having analyzed your colleagues posting and application. Or Offer your opinion and possible alternatives for solution details. Or Evaluate and validate an idea with your own experience. Or Make a suggestion and expand on below In application programs, a hashtable or hash map is one of the data structures used. It implements a hash function that maps a key to an index, which is the value associated with each element of an array. A non-null object of any data type can be sued as key as long as it can implement the hashCode and equals methods. The slot or memory location that corresponds to the index contains the data or information that the user is searching for. An ideal hashtable uses a hash function with which a unique index is calculated for each key. In case of collision, in which more than one keys correspond to the same index, the records are stored and searched sequentially using an extended hash function (Oracle, n.d.). A scenario for which a hashtable can be used is in searching for a book from a small to medium electronic catalog or database. In library databases, books and other reference materials are usually identified by a number such as the account number. However, nearly all users do not know the identifying number of the book that they are looking for. With hashtable, a user can specify other information about the book such as the title and/or author (Oracle, n.d.). Since different books may have the same author(s), the search results will include a list of all books with the specified author(s). Compared to tree search structures such as JTrees and other table lookup structures such as ArrayList, hashtables are generally more efficient. Perhaps this higher efficiency is due to the tradeoff between the overhead space and the time cost of rehashing that can be selected based on system or user requirements. This is the main reason that hashtables are commonly used in database indexing (Oracle, n.d.). Like an array or an ArrayList, a hashtable is initialized or instantiated by specifying its size or initial capacity. The latter suggests that a hashtable is more like an ArrayList whose size is not fixed. However, the capacity or number of slots of a hashtable is increased only when the load factor is reached.