Describe Stream interface and Stream pipeline

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stream pipeline

Having seen some examples of Stream usage, now its time for official documents of Stream Interface.

public interface Stream<T>
extends BaseStream<T,Stream<T>>

A sequence of elements supporting sequential and parallel aggregate operations. The following example illustrates an aggregate operation using Stream and IntStream:

     int sum = widgets.stream()
                      .filter(w -> w.getColor() == RED)
                      .mapToInt(w -> w.getWeight())
                      .sum();
 

In this example, widgets is a Collection<Widget>. We create a stream of Widget objects via Collection.stream(), filter it to produce a stream containing only the red widgets, and then transform it into a stream of int values representing the weight of each red widget. Then this stream is summed to produce a total weight.

We will study more examples later.