On Java 8 Examples

To run the code examples from the On Java 8 book, you must first install JDK 8. After downloading and unzipping the repository, navigate to the root directory (where gradlew and gradlew.bat are located) and run the Gradle wrapper tests. An internet connection is required for the first run to allow Gradle to download necessary dependencies.

Important Compatibility Note: Do not use JDK 16 or greater with Gradle in this repository, as it will produce a BUG! message.

Use your distribution's package manager to install the JDK.

# Ubuntu/Debian
sudo apt-get update
sudo apt-get install default-jdk

# Fedora/Redhat
su -c "yum install java-1.8.0-openjdk"

The following commands are essential for navigating the project structure and managing files. Note the differences between Unix-based systems (Mac/Linux) and Windows.

To install Java on macOS, use Homebrew. Note that if the installed version is too recent, macOS security might block it, requiring manual security adjustments or an earlier version installation.

brew update
brew cask install java

To run the book's examples, you will need to use a command-line shell. Use the following methods to open one:

• Mac: Open Spotlight (magnifying glass icon), type "terminal", and press Return.
• Windows:
  • Windows 7: Search for "explorer" in the Start Menu and press Enter.
  • Windows 8: Press Windows+Q, type "explorer", and press Enter.
  • Windows 10: Press Windows+E.
  • Once Explorer is open, navigate to your desired folder, click the file tab at the top left, and select "Open Windows Powershell".
• Linux:
  • Debian/Fedora: Press Alt+F2 and type gnome-terminal.
  • Ubuntu: Right-click the desktop and select "Open Terminal" or press Ctrl+Alt+T.
  • Redhat: Right-click the desktop and select "Open Terminal".

All commands must be run from the base directory where the gradlew script is located. On Unix/Linux systems, you must prefix commands with ./.

Running the project

• Compile and run everything: gradlew run (Unix: ./gradlew run)
• Run a specific program: gradlew <program_name> (e.g., gradlew ReplacingStringTokenizer)
• Run a program in a specific chapter: gradlew :<chapter>:<program_name> (e.g., gradlew :strings:ReplacingStringTokenizer)

Compiling

• Compile everything: gradlew compileJava (Unix: ./gradlew compileJava)
• Compile a specific chapter: gradlew :<chapter>:compileJava (e.g., gradlew :strings:compileJava)

Testing

• Run all tests: gradlew test (Windows) or ./gradlew test (Mac/Linux)

After installation, open a new shell and run the following command to ensure Java is correctly configured in your environment.

java -version

To install the Java Development Kit on Windows, use the Chocolatey package manager. You can install jdk8 or a more recent version like jdk11.

choco install jdk8

If a Gradle build fails with an SSLException related to trustAnchors, it typically indicates a conflict between multiple Java installations on your machine. The cacerts security file of one installation may be interfering with the one used by Gradle.

Error signature: javax.net.ssl.SSLException: java.lang.RuntimeException: Unexpected error: java.security.InvalidAlgorithmParameterException: the trustAnchors parameter must be non-empty

Resolution steps:

1. Identify all cacerts files on your machine.
2. Uninstall conflicting Java applications or remove the directory containing the interfering cacerts file.
3. Adjust environment variables or your system PATH if necessary.
4. Once Gradle works, reinstall required applications.