Java Reference
In-Depth Information
17.1
Introduction
17.2
Functional Programming
Technologies Overview
17.2.1 Functional Interfaces
17.2.2 Lambda Expressions
17.2.3 Streams
17.3
IntStream
Operations
17.3.1 Creating an
IntStream
and
Displaying Its Values with the
forEach
Terminal Operation
17.3.2 Terminal Operations
count
,
min
,
max
,
sum
and
average
17.3.3 Terminal Operation
reduce
17.3.4 Intermediate Operations: Filtering and
Sorting
IntStream
Values
17.3.5 Intermediate Operation: Mapping
17.3.6 Creating Streams of
int
s with
IntStream
Methods
range
and
rangeClosed
17.4
Stream<Integer>
Manipulations
17.4.1 Creating a
Stream<Integer>
17.4.2 Sorting a
Stream
and Collecting the
Results
17.4.3 Filtering a
Stream
and Storing the
Results for Later Use
17.4.4 Filtering and Sorting a
Stream
and
Collecting the Results
17.4.5 Sorting Previously Collected Results
17.5
Stream<String>
Manipulations
17.5.1
17.5.2 Filtering
String
s Then Sorting Them
in Case-Insensitive Ascending Order
17.5.3 Filtering
String
s Then Sorting Them
in Case-Insensitive Descending Order
17.6
Stream<Employee>
Manipulations
17.6.1 Creating and Displaying a
List<Employee>
17.6.2 Filtering
Employee
s with Salaries in a
Specified Range
17.6.3 Sorting
Employee
s By Multiple Fields
17.6.4 Mapping
Employee
s to Unique Last
Name
String
s
17.6.5 Grouping
Employee
s By Department
17.6.6 Counting the Number of
Employee
s
in Each Department
17.6.7 Summing and Averaging
Employee
Salaries
17.7
Creating a
Stream<String>
from a
File
17.8
Generating Streams of Random
Values
17.9
Lambda Event Handlers
17.10
Additional Notes on Java SE 8
Interfaces
17.11
Java SE 8 and Functional
Programming Resources
17.12
Wrap-Up
Mapping
String
s to Uppercase
Using a Method Reference
Summary | Self-Review Exercises | Answers to Self-Review Exercises | Exercises
The way you think about Java programming is about to change profoundly. Prior to Java
SE 8, Java supported three programming paradigms—
procedural programming
,
object-ori-
ented programming
and
generic programming
. Java SE 8 adds
functional programming
. The
new language and library capabilities that support this paradigm were added to Java as part
of
Project Lambda:
In this chapter, we'll define functional programming and show how to use it to write
programs faster, more concisely and with fewer bugs than programs written with previous
techniques. In Chapter 23, Concurrency, you'll see that functional programs are easier to
parallelize
(i.e., perform multiple operations simultaneously) so that your programs can
take advantage of multi-core architectures to enhance performance. Before reading this
chapter, you should review Section 10.10, which introduced Java SE 8's new interface fea-
