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What is the difference between a Set and a Map in Java?

Main differences between a Set and a Map in Java are:

  1. Duplicate Elements: A Set does not allow inserting duplicate elements. A Map does not allow using duplicate keys, but it allows inserting duplicate values for unique keys.
  2. Null values: A Set allows inserting maximum one null value. In a Map we can have single null key at most and any number of null values.
  3. Ordering: A Set does not maintain any order of elements. Some of sub-classes of a Set can sort the elements in an order like LinkedHashSet. A Map does not maintain any order of its elements. Some of its sub-classes like TreeMap store elements of the map in ascending order of keys.

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