[Java HashMap class]

HashMap is often used when developing in Java, so I summarized it as a review.

Map

It is managed by elements different from List, Set, and Queue. Map manages elements by the combination of key and value.

HashMap

HashMap is the most basic class of Map implementation class. The key cannot be duplicated. Has no turn.

Main methods of HashMap class

・ Int size ()

Get the number of elements in Map

・ Clear ()

Remove all elements

・ Get (Object key)

Get the value corresponding to key

・ KeySet ()

Get all keys

・ Put (key, value)

Add the specified key / value combination

・ IsEmpty ()

Determine if Map is empty

・ Remove (Object key)

Delete the specified key

-Collection values ()

Get all values

・ ContainsKey (Object key)

Determine if key is included in Map

・ ContainsValue (Object value)

Determine if value is included in Map

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