Tutorial by Topics: map

The java.util.Map interface represents a mapping between keys and their values. A map cannot contain duplicate keys; and each key can map to at most one value.

Since Map is an interface, then you need to instantiate a concrete implementation of that interface in order to use it; there are several Map implementations, and mostly used are the java.util.HashMap and java.util.TreeMap

Maps are data types used for storing unordered key-value pairs, so that looking up the value associated to a given key is very efficient. Keys are unique. The underlying data structure grows as needed to accommodate new elements, so the programmer does not need to worry about memory management. They are similar to what other languages call hash tables, dictionaries, or associative arrays.

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