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This article mainly introduces the relevant knowledge of how to use Java8's Stream, the content is detailed and easy to understand, the operation is simple and fast, and it has a certain reference value. I believe you will gain something after reading this article on how to use Java8's Stream. Let's take a look at it.

One: what is Stream?

Stream (stream) is a queue of elements from a data source and supports aggregation operations

Stream in Java does not store elements, but is calculated on demand. The source of the data source stream. It can be a collection, an array, an channel O channel, a generator generator, etc.

Aggregate operations are similar to SQL statements, such as filter, map, reduce, find, match, sorted, and so on. Unlike previous Collection operations, Stream operations have two basic characteristics as follows:

Pipelining: intermediate operations return the stream object itself. Such multiple operations can be concatenated into a single pipe, just like a streaming style. Doing so can optimize the operation, such as delayed execution and short circuit.

Internal iteration: in the past, the collection was traversed through Iterator or For-Each, explicitly iterating outside the collection, which is called > external iteration. Stream provides a way to iterate internally through the Visitor pattern (Visitor).

Second: Stream API uses 1: use Stream step: (1) first generate a stream (Stream) a data source, get a stream.

(2) the intermediate chain operates an intermediate operation chain to process the data of the data source.

(3) generate a new stream: a terminate operation, perform an intermediate operation, and produce a result.

Note: Stream operations are deferred, and they will wait until the results are needed.

Summary:

The common methods of intermediate operations are: filtering: filter mapping: map sorting: sorted extraction and combination collection: collect.

Termination operation: traversal: foreach matching: find, match protocol: reduce aggregation: max, min, count.

2: four ways to create Stream [1] methods in Collection interface: default Stream stream () get serial flow default Stream parallelStream () get parallel flow case: / / method of 1:Collection interface Collection collection = new ArrayList (); Stream stream = collection.stream (); Stream stream1 = collection.parallelStream () / / Mode 2: create an infinite stream (resulting in wireless) through the Stream method array IntStream stream2 = Arrays.stream (new int [] {1,2,3,4,5}) in Arrays; / / of method Stream stream3 = Stream.of ("111,222,333") in mode 3:Stream; / / method 4:Stream (resulting in wireless). 3: intermediate operation 1: screening and slicing

① Stream filter (Predicate

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