A hash table in programming is a collection that uses a hash function to map identifying values (keys) to their associated values.
The basic advantage of a hash table is that they provide very efficient lookup and search functionality. Unlike many other linear collection types (such as arrays and linked lists), one does not have to loop through all the elements in a hash table searching for a particular entity.
For Java: https://docs.oracle.com/javase/8/docs/api/java/util/Hashtable.html