Java Streams

Java Stream Introduction

A stream is a sequence of data values supporting sequential and parallel aggregate operations.

• Using aggregate functions we can sum all sales figures for a month, region or product.
• Aggregate operations work on a list of items and produces a single value.
• The result of an aggregate operation on stream may be primative value, an object or a void for Stream.

Collections Vs Streams

Collections

• Java Collections focus on how to store data elements for efficient access.

Storage

Java Collection is an in-memory data structure that stores all its elements.

Infinite Streams

Java Collection cannot reprsent a group of infinate elements

---

Streams

• Java Streams focus on aggregate operations on data elements from a data source.

Storage

Java Streams has no storage.
Java stream pulls elements from a data source on-demand and passes them to a pipeline of operations for processing.
Java Streams we focus on operations Example (Aggregates)

Infinite Streams

Java Streams can reprsent a group of infinate elements
Java Streams can pull its elements from data source. The data sourse can be a collection, a function that generates data, an I/O channel, etc.
A Java Stream can pull data from a function which generates infinate number of elements.

Reusability

Java Streams cannot be reusable after calling a teriminal operation.
To perform a computation on the same elements from the data source, we have to recrete the stream pipeline.
Java Streams can throw an illegalStateException in case of reusing