Java

Table of Contents generated with DocToc

• Documentation
• Tools and Frameworks
• Installing Java on Windows
• Installing Java on macOS
• Links

Documentation

• Rheinwerk<openbook>: Java ist auch eine Insel

• Baeldung - Baeldung Learning Materials, Courses and Guides

Tools and Frameworks

• JUnit5 class Assertions

• Baeldung: A Guide to JUnit5

Installing Java on Windows

One Java Version Only

• Chocolatey: temurin - Eclipse Temurin is a part of the Adoptium Enterprise Java Platform replacing AdopOpenJDK.

• Chocolatey: maven

Switching Between Multiple Versions of Java using SDKMAN

You can install either in a GitBaSH or into Ubuntu on WSL-2.

For GitBaSH you need MinGW-x64 and the zip (and unzip) tools. I am installing them using Chocolatey:

choco install git mingw zip

For Ubuntu in WSL-2 you need zip and unzip:

sudo apt install unzip zip

Next, install SDKMAN

Finally, install the desired java version(s):

sdk list java
...
sdk install java 17.0.7-tem

If you are using JetBrains IntelliJ IDEA, then you can add your Java SDKs via the File -> Project Structure dialog on the Project or Platform Settings/SDKs views. The base folder for the SDK is in C:\Users\yourname\.sdkman\candidates\java\17.0.7-tem (as an example for java 17 temurin).

Installing Java on macOS

One Java Version Only

On macOS I am installing java by means of Homebrew:

brew install temurin

This will download and install the latest OpenJDK provided by the Adoptium project.

For code development I am using JetBrains IntelliJ IDEA whom I wish to thank for the free license they grant to me because of my open source contributions.

Please check the list of IntelliJ IDEA Plugins I recommend.

Switching Between Multiple Versions of Java

Works For Both Java And Gradle

1. Install sdkman

2. Install java and gradle

   # Install latest
   sdk install java
   sdk install gradle
   
   # Install an alternative version
   sdk install java 11-ms
   sdk install gradle 6.7.1
   

3. Select a default version for java and gradle

   sdk default java 11.0.14-ms
   sdk default gradle 6.7.1
   

4. Use a different version of java and gradle in the current shell (restored to default in the next shell)

   sdk use java 11-ms
   sdk use gradle 6.7.1
   

Works For Java, Doesn’t Work For Gradle

1. Install jenv

   brew install jenv
   # Remember to add the initialization code to .zshrc or .bashrc
   # Restart your shell
   

2. Install some Java versions using Homebrew

   brew tap homebrew/cask-versions
   brew install temurin
   brew install temurin11
   

3. Find out the Java version paths

   /usr/libexec/java_home -V
   

4. Register the Java version paths with jenv

   jenv add ... # for each Java version you'd like to switch to
   

5. Verify

   jenv versions
   

6. Switch Java version (e.g. 11)

   jenv global 11
   

7. In a specific directory, select a different Java version (e.g. 17)

   jenv local 17
   

API Services and Web Applications

• Hot Swapping - Live reload classes and web content.
• Serving Web Content with Spring MVC - Guide to creating a simple MVC web application.
  • Testing the Web Layer - Guide to testing a simple MVC web application.
  • Spring Docs: Testing - Reference manual for testing spring applications.
• HtmlUnit - GUI-Less browser for Java programs.
  • HtmlUnit 2.60.0 API Documentation - JavaDoc for all HtmlUnit classes.

Links

• Adoptium - Prebuilt OpenJDK Binaries for Free.
• JetBrains IntelliJ IDEA - Java IDE.
• Stackoverflow: Mac OS X and multiple Java versions