Wednesday, April 21, 2021

Modern JAVA: What is the difference between intermediate and terminal operations?

Source:

"A Stream supports several operations and these operations are divided into intermediate and terminal operations.

The distinction between this operations is that an intermediate operation is lazy while a terminal operation is not. When you invoke an intermediate operation on a stream, the operation is not executed immediately. It is executed only when a terminal operation is invoked on that stream. In a way, an intermediate operation is memorized and is recalled as soon as a terminal operation is invoked. You can chain multiple intermediate operations and none of them will do anything until you invoke a terminal operation. At that time, all of the intermediate operations that you invoked earlier will be invoked along with the terminal operation.

All intermediate operations return Stream (can be chained), while terminal operations don't. 


Intermediate Operations are:

filter(Predicate<T>)  map(Function<T>)  flatMap(Function<T>)  sorted(Comparator<T>)  peek(Consumer<T>)  distinct()  limit(long n)  skip(long n)  

Terminal operations produces a non-stream (cannot be chained) result such as primitive value, a collection or no value at all.

Terminal Operations are:

forEach  forEachOrdered  toArray  reduce  collect  min  max  count  anyMatch  allMatch  noneMatch  findFirst      findAny  

Last 5 are short-circuiting terminal operations"


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