Book Image

The Java Workshop

By : David Cuartielles, Andreas Göransson, Eric Foster-Johnson
Book Image

The Java Workshop

By: David Cuartielles, Andreas Göransson, Eric Foster-Johnson

Overview of this book

Java is a versatile, popular programming language used across a wide range of industries. Learning how to write effective Java code can take your career to the next level, and The Java Workshop will help you do just that. This book is designed to take the pain out of Java coding and teach you everything you need to know to be productive in building real-world software. The Workshop starts by showing you how to use classes, methods, and the built-in Collections API to manipulate data structures effortlessly. You’ll dive right into learning about object-oriented programming by creating classes and interfaces and making use of inheritance and polymorphism. After learning how to handle exceptions, you’ll study the modules, packages, and libraries that help you organize your code. As you progress, you’ll discover how to connect to external databases and web servers, work with regular expressions, and write unit tests to validate your code. You’ll also be introduced to functional programming and see how to implement it using lambda functions. By the end of this Workshop, you’ll be well-versed with key Java concepts and have the knowledge and confidence to tackle your own ambitious projects with Java.

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The Java Workshop
David Cuartielles | Andreas Göransson | Eric Foster-Johnson
Oct, 2019 | 606 pages
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Table of Contents (20 chapters)
Preface
Preface
About the Book
Free Chapter
1
1. Getting Started
1. Getting Started
Introduction
Writing, Compiling, and Executing Your Hello World Program
Summary
2
2. Learning the Basics
2. Learning the Basics
Introduction
Controlling the Flow of Your Programs
Looping and Performing Repetitive Tasks
Handling Command-Line Arguments
Summary
3
3. Object-Oriented Programming
3. Object-Oriented Programming
Introduction
Working with Objects in Java
Checking the Precedence of a Class with instanceof
Inheritance in Java
Overriding and Hiding Methods
Overloading Methods and Constructors
Recursion
Annotations
Interfaces
Inner Classes
Documenting with JavaDoc
Summary
4
4. Collections, Lists and Java's Built-In APIs
4. Collections, Lists and Java's Built-In APIs
Introduction
Arrays
Sets
Lists
Maps
Iterating through Collections
Sorting Collections
Properties
Summary
5
5. Exceptions
5. Exceptions
Introduction
A Simple Exception Example
NullPointerException – Have No Fear
Catching Exceptions
Throws and Throw
The finally Block
Best Practices for Handling Exceptions
Where Do Exceptions Come from?
Summary
6
6. Libraries, Packages, and Modules
6. Libraries, Packages, and Modules
Introduction
Organizing Code into Packages
Summary
7
7. Databases and JDBC
7. Databases and JDBC
Introduction
Relational Databases
Relational Database Management Systems
Introducing SQL
Summary
8
8. Sockets, Files, and Streams
8. Sockets, Files, and Streams
Introduction
Listing Files and Directories
Creating and Writing to a File
Reading an Existing File
Reading a Properties File
Summary
9
9. Working with HTTP
9. Working with HTTP
Introduction
Exploring HTTP
Using HttpUrlConnection
Dealing with Slow Connections
Creating HTTP POST Requests
Parsing HTML Data
Delving into the java.net.http Module
Summary
10
10. Encryption
10. Encryption
Introduction
Symmetric Key Encryption
Block Ciphers
Asymmetric Key Encryption
Encrypting Files
Summary
11
11. Processes
11. Processes
Introduction
Launching a Process
Capturing the Output of a Child Process
Storing the Output of a Child Process in a File
Summary
12
12. Regular Expressions
12. Regular Expressions
Introduction
Decrypting Regular Expressions
Regular Expressions in Java
Summary
13
13. Functional Programming with Lambda Expressions
13. Functional Programming with Lambda Expressions
Introduction
Functional Programming
Pure Functions
Lambda Expressions
Summary
14
14. Recursion
14. Recursion
Introduction
Delving into Recursion
Summary
15
15. Processing Data with Streams
15. Processing Data with Streams
Introduction
Creating Streams
Intermediate Operations
Using Collectors
Summary
16
16. Predicates and Other Functional Interfaces
16. Predicates and Other Functional Interfaces
Introduction
Predicate Interface
Activity 1: Toggling the Sensor States
Function
Summary
17
17. Reactive Programming with Java Flow
17. Reactive Programming with Java Flow
Introduction
Publisher
Subscriber
Processor
Summary
18
18. Unit Testing
18. Unit Testing
Introduction
Getting Started with Unit Tests
Summary
Appendix
Appendix
1. Getting Started
2. Learning the Basics
3. Object-Oriented Programming
4. Collections, List, and Java's Built-In APIs
5. Exceptions
6. Libraries, Packages, and Modules
7. Databases and JDBC
8. Sockets, Files, and Streams
9. Working with HTTP
11. Processes
12. Regular Expressions
13. Functional Programming with Lambda Expressions
14. Recursion
15. Processing Data with Streams
16. Predicates and Other Functional Interfaces
17. Reactive Programming with Java Flow
18. Unit Testing
What Next?

Listing Files and Directories

We are going to examine how to list files and directories in different ways. These techniques can come in handy when checking whether a certain file exists, which will allow you to give more sensitive information to users when, for example, trying to find a properties file. If you detect that the file you're looking for doesn't exist and, at the same time, you notice that you are not in the right directory, you could make your program locate the actual folder in which the file resides, or you could simply inform the user about this situation.

Note

There are different techniques to list the files and directories at any location on your computer. You must choose wisely depending on the circumstances. While the latest API seems more complex at first sight, as you will see in the following examples, it is a lot more powerful than any of the previous versions.

Let's start with the old way of listing the contents of a directory. In the...

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