#### Overview of this book

Java 9 Data Structures and Algorithms covers classical, functional, and reactive data structures, giving you the ability to understand computational complexity, solve problems, and write efficient code. This book is based on the Zero Bug Bounce milestone of Java 9. We start off with the basics of algorithms and data structures, helping you understand the fundamentals and measure complexity. From here, we introduce you to concepts such as arrays, linked lists, as well as abstract data types such as stacks and queues. Next, we’ll take you through the basics of functional programming while making sure you get used to thinking recursively. We provide plenty of examples along the way to help you understand each concept. You will also get a clear picture of reactive programming, binary searches, sorting, search trees, undirected graphs, and a whole lot more!
Java 9 Data Structures and Algorithms
Credits
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Preface
Free Chapter
Why Bother? – Basic
Cogs and Pulleys – Building Blocks
Protocols – Abstract Data Types
Detour – Functional Programming
Efficient Searching – Binary Search and Sorting
Efficient Sorting – quicksort and mergesort
Concepts of Tree
More About Search – Search Trees and Hash Tables
Concepts of Graph
Reactive Programming
Index

## The tree abstract data type

Now that we have some idea of the tree, we can define the tree ADT. A tree ADT can be defined in multiple ways. We will check out two. In an imperative setting, that is, when trees are mutable, we can define a tree ADT as having the following operations:

• Get the root node

• Given a node, get its children

This is all that is required to have a model for a tree. We may also include some appropriate mutation methods.

The recursive definition for the tree ADT can be as follows:

• A tree is an ordered pair containing the following:

• a value

• a list of other trees, which are meant to be it's subtrees

We can develop a tree implementation in exactly the same way as it is defined in the functional tree ADT:

```public class FunctionalTree<E> {
private E value;
`    public FunctionalTree(E value, LinkedList<FunctionalTree...`