long count() returns the count of elements in the stream. This is a special case of a reduction (A reduction operation takes a sequence of input elements and combines them into a single summary result by repeated application of a combining operation). This is a terminal operation i.e, it may traverse the stream to produce a result or a side-effect. After the terminal operation is performed, the stream pipeline is considered consumed, and can no longer be used.
Note : The return value of count operation is the count of elements in the stream.
Example 1 : Counting number of elements in array.
Example 2 : Count number of distinct elements in a list.
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