Streams were also new in Java 8, just like lambda expressions. They work together very strongly, so their appearance at the same time is not a surprise. Lambda expressions as well as streams support the functional programming style.

The very first thing to clarify is that streams do not have anything to do with input and output streams, except the name. They are totally different things. Streams are more like collections with some significant differences. (If there were no differences, they would just have been collections.) Streams are essentially pipelines of operations that can run sequentially or in parallel. They obtain their data from collections or other sources, including data that is manufactured on-the-fly.

Streams support ...

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