If you want to experiment with the code examples from the book [On Java

8](https://www.onjava8.com/), you're in the right place.

These examples are automatically extracted directly from the book. This repository

includes tests to verify that the code in the book is correct.

- [Building From the Command Line: Quick Version](#building-from-the-command-line-quick-version)

- [Building From the Command Line: Detailed Instructions](#building-from-the-command-line-detailed-instructions)

* [Install Java](#install-java)

+ [Windows](#windows)

+ [Macintosh](#macintosh)

+ [Linux](#linux)

* [Verify Your Installation](#verify-your-installation)

* [Installing and Running the Book Examples](#installing-and-running-the-book-examples)

- [Appendix A: Command-Line Basics](#appendix-a-command-line-basics)

* [Editors](#editors)

* [The Shell](#the-shell)

+ [Starting a Shell](#starting-a-shell)

+ [Directories](#directories)

+ [Basic Shell Operations](#basic-shell-operations)

+ [Unpacking a Zip Archive](#unpacking-a-zip-archive)

- [Appendix B: Testing](#appendix-b-testing)

- [Troubleshooting](#troubleshooting)

Before you can run the examples from this repository, you must install

[JDK8](http://www.oracle.com/technetwork/java/javase/downloads/index.html), the

*Java Development Kit* for version 8 of the language.

If you just want to download and check the code, [Download

Here](https://github.com/BruceEckel/OnJava8-Examples/archive/refs/heads/master.zip)

and [unzip it](#unpacking-a-zip-archive) into your destination directory. Open

a [shell/command window](#appendix-a-command-line-basics) and move into the

root of that directory. You'll know you are in the right directory if you see

the files `gradlew` and `gradlew.bat`.

You'll need an Internet connection the first time you compile the code,

because Gradle needs to first install itself, then all the support libraries.

Once these are installed you can perform additional compiling and running

offline.

On Mac/Linux, enter:

(If you get a *Permission denied* error, run `chmod +x ./gradlew`)

On Windows, enter

If all goes well, the tests will run. Everything should complete without errors.

All the book examples are in the subdirectory `Examples` in subdirectories

corresponding to the atom names.

If you are not familiar with the command line, first read [Command-Line

Basics](#appendix-a-command-line-basics).

You must first install the *Java Development Kit* (JDK).

1. Follow the instructions to [install Chocolatey](https://chocolatey.org/).

2. At a [shell prompt](#appendix-a-command-line-basics), type: `choco install

jdk8` (you may also select a more recent version, like `jdk11`). The

installation process takes some time, but when it's finished Java is installed

and the necessary environment variables are set.

The Mac comes with a much older version of Java that won't work for the

examples in this book, so you'll need to update it to (at least) Java 8.

1. Follow the instructions at this link to [Install HomeBrew](http://brew.sh/)

2. At a [shell prompt](#appendix-a-command-line-basics), first type

`brew update`. When that completes, enter `brew cask install java`.

**NOTE:** Sometimes the default version of Java that you get with the above

installation will be too recent and not validated by the Mac's security

system. If this happens you'll either need to turn off the security by hand

or install an earlier version of Java. For either choice, you'll need to Google

for answers on how to solve the problem (often the easiest approach is to just

search for the error message produced by the Mac).

Use the standard package installer with the following [shell commands](#appendix-a-command-line-basics):

*Ubuntu/Debian*:

1. `sudo apt-get update`

2. `sudo apt-get install default-jdk`

*Fedora/Redhat*:

[Open a new shell](#appendix-a-command-line-basics) and type:

You should see something like the following (Version numbers and actual text

will vary):

If you see a message that the command is not found or not recognized, review

the installation instructions. If you still can't get it to work, check

[StackOverflow](http://stackoverflow.com/search?q=installing+java).

Once you have Java installed, the process to install and run the book examples

is the same for all platforms:

1. Download the book examples from the

[GitHub Repository](https://github.com/BruceEckel/OnJava8-Examples/archive/refs/heads/master.zip).

2. [Unzip](#unpacking-a-zip-archive) the downloaded file into the directory of your choice.

3. Use the Windows Explorer, the Mac Finder, or Nautilus or equivalent on Linux

to browse to the directory where you uzipped `OnJava8-Examples`, and

[open a shell](#appendix-a-command-line-basics) there.

4. If you're in the right directory, you should see files named `gradlew` and

`gradlew.bat` in that directory, along with numerous other files and

directories. The directories correspond to the chapters in the book.

5. At the shell prompt, type `gradlew test` (Windows) or `./gradlew test`

(Mac/Linux).

The first time you do this, Gradle will install itself and numerous other

packages, so it will take some time. After everything is installed, subsequent

builds and runs will be much faster.

Note that you must be connected to the Internet the first time you run `gradlew`

so that Gradle can download the necessary packages.

Because it is possible for a "dedicated beginner" to learn programming from

this book, you may not have previously used your computer's command-line shell.

If you have, you can go directly to the

[installation instructions](#building-from-the-command-line-detailed-instructions).

To create and modify Java program files—the code listings shown in this

book—you need a program called an *editor*. You'll also need the editor to

make changes to your system configuration files, which is sometimes required

during installation.

Programming editors vary from heavyweight *Integrated Development Environments*

(IDEs, like Eclipse, NetBeans and IntelliJ IDEA) to more basic text

manipulation applications. If you already have an IDE and are comfortable with

it, feel free to use that for this book.

Numerous explanations in this book are specific to IntelliJ IDEA so if you

don't already have an IDE you might as well start with IDEA. There are many

other editors; these are a subculture unto themselves and people sometimes get

into heated arguments about their merits. If you find one you like better, it's

not too hard to change. The important thing is to choose one and get

comfortable with it.

If you haven't programmed before, you might be unfamiliar with your operating

system *shell* (also called the *command prompt* in Windows). The shell harkens

back to the early days of computing when everything happened by typing commands

and the computer responded by displaying responses—everything was text-based.

Although it can seem primitive in the age of graphical user interfaces, a shell

provides a surprising number of valuable features.

To learn more about your shell than we cover here, see

[Bash Shell](https://en.wikipedia.org/wiki/Bash_(Unix_shell)) for Mac/Linux

or [Windows Shell](https://en.wikipedia.org/wiki/Windows_shell).

**Mac**: Click on the *Spotlight* (the magnifying-glass icon in the upper-right

corner of the screen) and type "terminal." Click on the application that looks

like a little TV screen (you might also be able to hit "Return"). This starts a

shell in your home directory.

**Windows**: First, start the Windows Explorer to navigate through your

directories:

- *Windows 7*: click the "Start" button in the lower left corner of the screen.

In the Start Menu search box area type "explorer" and then press the "Enter"

key.

- *Windows 8*: click Windows+Q, type "explorer" and then press the "Enter" key.

- *Windows 10*: click Windows+E.

Once the Windows Explorer is running, move through the folders on your computer

by double-clicking on them with the mouse. Navigate to the desired folder. Now

click the file tab at the top left of the Explorer window and select "Open

Windows Powershell." This opens a shell in the destination directory.

**Linux**: To open a shell in your home directory:

- *Debian*: Press Alt+F2. In the dialog that pops up, type 'gnome-terminal'

- *Ubuntu*: Either right-click on the desktop and select 'Open Terminal', or

press Ctrl+Alt+T

- *Redhat*: Right-click on the desktop and select 'Open Terminal'

- *Fedora*: Press Alt+F2. In the dialog that pops up, type 'gnome-terminal'

*Directories* are one of the fundamental elements of a shell. Directories hold

files, as well as other directories. Think of a directory as a tree with

branches. If `books` is a directory on your system and it has two other

directories as branches, for example `math` and `art`, we say that you have a

directory `books` with two *subdirectories* `math` and `art`. We refer to them

as `books/math` and `books/art` since `books` is their *parent* directory.

Note that Windows uses backslashes rather than forward slashes to separate the

parts of a directory.

The shell operations shown here are approximately identical across operating

systems. For the purposes of this book, here are the essential operations in a

shell:

- **Change directory**: Use `cd` followed by the name of the

directory where you want to move, or `cd ..` if you want to move

up a directory. If you want to move to a different directory while

remembering where you came from, use `pushd` followed by the different

directory name. Then, to return to the previous directory, just say

`popd`.

- **Directory listing**: `ls` (`dir` in Windows) displays all the files and

subdirectory names in the current directory. Use the wildcard `*` (asterisk) to

narrow your search. For example, if you want to list all the files ending in

".kt," you say `ls *.kt` (Windows: `dir *.kt`). If you want to list the

files starting with "F" and ending in ".kt," you say `ls F*.kt` (Windows:

`dir F*.kt`).

- **Create a directory**: use the `mkdir` ("make directory") command

(Windows: `md`), followed by the name of the directory you want to create.

For example, `mkdir books` (Windows: `md books`).

- **Remove a file**: Use `rm` ("remove") followed by the name of the file

you wish to remove (Windows: `del`). For example, `rm somefile.kt` (Windows:

`del somefile.kt`).

- **Remove a directory**: use the `rm -r` command to remove the files in

the directory and the directory itself (Windows: `deltree`). For example,

`rm -r books` (Windows: `deltree books`).

- **Repeat a command**: The "up arrow" on all three operating

systems moves through previous commands so you can edit and

repeat them. On Mac/Linux, `!!` repeats the last command and

`!n` repeats the nth command.

- **Command history**: Use `history` in Mac/Linux or press the F7 key in Windows.

This gives you a list of all the commands you've entered. Mac/Linux provides

numbers to refer to when you want to repeat a command.

A file name ending with `.zip` is an archive containing other files in a

compressed format. Both Linux and Mac have command-line `unzip` utilities, and

it's possible to install a command-line `unzip` for Windows via the Internet.

However, in all three systems the graphical file browser (Windows Explorer, the

Mac Finder, or Nautilus or equivalent on Linux) will browse to the directory

containing your zip file. Then right-mouse-click on the file and select "Open"

on the Mac, "Extract Here" on Linux, or "Extract all ..." on Windows.

The test system is built in so that we (the authors) can verify the correctness

of what goes into the book.

You don't need to run the tests, but if you want to, you can just run `gradlew

test` (on Windows) or `./gradlew test` (Mac/Linux).

However, if the file name is unique throughout the book (the majority are), you

can just give the program name, like this:

Note that all commands are run from the base directory where the example code is

installed, and where you find the `gradlew` script.

If any terminology or processes described here remain unclear to you, you can

usually find explanations or answers through [Google](https://www.google.com/).

For more specific issues or problems, try

[StackOverflow](http://stackoverflow.com/). Sometimes you can find installation

instructions on [YouTube](https://www.youtube.com/).

Sometimes a Gradle build will be unable to connect to the internet and download

the necessary components, producing an error message containing:

Normally this means you have multiple Java installations on your machine

(applications built with Java ordinarily install their own version of Java), and

somehow the `cacerts` security file is interfering with the `cacerts` file for

the Java you have installed. It can be difficult to know which `cacerts` file is

interfering with yours. The brute-force approach is to search for all the

`cacerts` files on your machine and begin uninstalling the associated

applications---or in some cases, simply removing the directory containing the

`cacerts` file---until the Gradle build begins to work. You might also need to

adjust some environment variables and/or your path. Once you get the Gradle

build working successfully, you should be able to reinstall any applications you

removed in the process.