Java 8 Stream Equivalents

What is Java 8 stream?

Since Java 8 was introduced in Java 8, the API stream has been used to process the collection of objects. Stream is a range of things that support various methods that help you create the desired result. Kotlin provides many extension methods in groups and goods to apply functional-style activities. A dedicated sequence type allows a lazy structure of such activities.

The features of the Java stream are:

  • 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.
  • Each intermediate operation is lazily executed and returns a stream. As a result, hence various medium operations can be pipelined. Terminal operations mark the end of the stream and return the result.

About laziness

If you want to lazy process a chain, you can convert it to a Sequence using sequence() before the chain. At the end of the chain of functions, you usually end up with a Sequence. Then you can use toList(), toSet(), toMap() or some other function to materialize the Sequence at the end.

Reusing Streams

In Kotlin, it depends on the type of collection and whether it can be consumed more than once. A Sequence generates a new iterator every time, and unless it asserts "use only once," it can reset to the start each time it is acted upon.

Different Operations on Streams:

Intermediate Operations

  1. Map: The map method returns a stream consisting of the results of applying the given function to the elements of this stream.
  2. Filter: The filter method selects elements per the Predicate passed as an argument.
  3. Sorted: The sorted method is used to sort the stream.

Terminal Operations

  1. collect: The collect method is used to return the result of the intermediate operations performed on the stream.
  2. forEach: The forEach method is used to iterate through every stream element.
  3. Reduce: The reduce method is used to reduce the elements of a stream to a single value. The reduce method takes a Binary Operator as a parameter.