Stream

• The concept of Stream is integrated/introduced in Java 8.
• The Stream API is used to process collections of objects.
• A stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result.
• A stream is not a data structure instead it takes input from the Collections, Arrays or I/O channels.
• Streams don’t change the original data structure, they only provide the result as per the pipelined methods.
• The Stream Classes in Java supports Functional Programming Paradigm and Parallel Programming
• Intermediate operations return a stream as a result
• Intermediate operations can be chained together to form a pipeline of operations.
• Pipeline of operations may contain any number of intermediate operations, but there has to be only one terminal operation, that too at the end of pipeline.
• Intermediate operations are lazily loaded. 


  When you call intermediate operations, they are actually not executed.
• When you call intermediate operations, they are actually not executed.


  They are just stored in the memory and executed when the terminal operation is called on the stream.
• Intermediate operations don’t give end result.

  They just transform one stream to another stream.
• Terminal operations return non-stream values like primitive or object or collection or may not return anything.
• Terminal operations cannot be chained together.
• Terminal operations give end result.
• filter()


  Returns a stream of elements which satisfy the given predicate.
• map()


  Returns a stream consisting of results after applying given function to

  elements of the stream.
• distinct()


  Returns a stream of unique elements.
• sorted()


  Returns a stream consisting of elements sorted according to natural

  order.
• limit()


  Returns a stream containing first n elements.
• skip()


  Returns a stream after skipping first n elements.
• forEach()


  Performs an action on all elements of a stream.
• toArray()


  Returns an array containing elements of a stream.
• reduce()


  Performs reduction operation on elements of a stream using initial value and binary operation.
• collect()


  Returns mutable result container such as List or Set.
• min()


  Returns minimum element in a stream wrapped in an Optional object.
• max()


  Returns maximum element in a stream wrapped in an Optional object.
• count()


  Returns the number of elements in a stream.
• anyMatch()


  Returns true if any one element of a stream matches with given predicate.
• allMatch


  Returns true if all the elements of a stream matches with given predicate.
• noneMatch()


  Returns true only if all the elements of a stream doesn't match with given predicate.
• findFirst()


  Returns first element of a stream wrapped in an Optional object.
• findAny()


  Randomly returns any one element in a stream.