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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


A map is an object which store keys with an associated value for each key. A key and its value are sometimes called a key/value pair or an entry. Maps typically provide these features:

The most commonly used map implementation is HashMap. It works well with keys that are strings or numbers.

Plain maps such as HashMap are unordered. Iterating through key/value pairs may return individual entries in any order. If you need to iterate through map entries in a controlled fashion, you should look at the following:

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