Introduction

Lambda expressions described and demonstrated in the previous chapter were introduced in Java 8. Together with functional interfaces, they added the functional programming capability to Java, allowing the passing of behavior (functions) as parameters to the libraries optimized for the performance of data processing. This way, an application programmer can concentrate on the business aspects of the developed system, leaving performance aspects to the specialists—the authors of the library.

One example of such a library is the java.util.stream package, which is going to be the focus of this chapter. This package allows you to have a declarative presentation of the procedures that can be subsequently applied to the data, also in parallel; these procedures are presented as streams, which are objects of the Stream interface. For a better transition from the traditional collections to streams, two default methods (stream() and parallelStream()) were added to the java.util.Collection...