What is the Map interface?

Map is a generic interface of the Collections API defined as follows:

interface Map <key, value>

The Map interface defines a family of collection classes that map keys to values. There are generally no restrictions on the class of a key or the class of a value. Each key corresponds to a single value. A Map cannot contain duplicate keys. However, duplicate values are allowed.

The important methods of the Map interface are as follows:

• put(key, value): This method is used to insert a value into a Map.
• get(key): This method is used to obtain a value from a Map.

Methods in the Map interface throw the following exceptions:

• ClassCastException: This exception is thrown when an object is incompatible with the elements of a Map.
• NoSuchElementException: This exception is thrown when a Map is empty.
• NullPointerException: This exception is thrown when an attempt is made to add a null value to the class that does not accept null.
• UnSupportedOperationException: This exception is thrown when an attempt is made to modify an unmodifiable Map.

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