Quick Start Guide: Java Setup for R Projects

This guide will walk you through downloading, installing, and managing Java environments for your R projects using the rJavaEnv package. We’ll cover setting up the environment, unsetting it, managing distributions, installing Java, and checking Java versions.

Step 1: Download and Install Java

Install rJavaEnv: First, install the development version of rJavaEnv from GitHub:
```
devtools::install_github("e-kotov/rJavaEnv")
```

Quick Install Java: To quickly install Java 21 (default) in your current project directory and set the environment:

library(rJavaEnv)
java_quick_install()

This command:

Downloads the Java distribution compatible with your OS and architecture.
Installs Java in a cache directory.
Sets the JAVA_HOME and PATH environment variables for the current session and project.

Expected output:

Platform detected or provided: <your_platform>
Architecture detected or provided: <your_architecture>
Downloading Java 21 (Corretto) for <your_platform> <your_architecture> to <destination_path>
Download completed.
Java 21 (Corretto) for <your_platform> <your_architecture> installed at <installed_path> and symlinked to <symlink_path>

Step-by-Step Installation: If you prefer a more controlled process:

Download Java:

java_distr_path <- java_download(version = 21, distribution = "Corretto")

This will download Java 21 from the Corretto distribution.

Expected output:

Downloading Java 21 (Corretto) for <your_platform> <your_architecture> to <destination_path>
Download completed.

Install Java:
```
java_home_path <- java_install(java_distr_path)
```
This will install the downloaded Java distribution and set the JAVA_HOME and PATH environment variables.

Expected output:
```
Java 21 (Corretto) installed at <installed_path> and symlinked to <symlink_path>
```

Step 2: Set Java Environment

Set the JAVA_HOME and PATH environment variables to the installed Java directory:

java_env_set(java_home_path)

This function sets the JAVA_HOME and PATH environment variables for the current R session and/or the project .Rprofile file.

Expected output:

Current R Session: JAVA_HOME and PATH set to <java_home_path>
Current R Project/Working Directory: JAVA_HOME and PATH set to <java_home_path> in .Rprofile in <project_directory>

Step 3: Unset Java Environment

Remove the JAVA_HOME and PATH environment variables settings from the project .Rprofile file:

java_env_unset()

This function removes the JAVA_HOME and PATH environment variables from the .Rprofile file in the project directory.

Expected output:

Removed JAVA_HOME settings from .Rprofile in <project_directory>

Step 4: Manage Java Distributions

List Cached Java Distributions:
```
java_list(type = "distrib")
```
This function lists all Java distributions cached in the user-specific data directory.

Expected output:
```
<data.frame or vector of cached Java distributions>
```
Clear Cached Java Distributions:
```
java_clear(type = "distrib")
```
This function clears all cached Java distributions.

Expected output:
```
Java distributions cache cleared.
```

Step 5: Manage Installed Java Versions

List Installed Java Versions:
```
java_list(type = "installed")
```
This function lists all installed Java versions in the user-specific data directory.

Expected output:
```
<data.frame or vector of installed Java versions>
```
Clear Installed Java Versions:
```
java_clear(type = "installed")
```
This function clears all installed Java versions.

Expected output:
```
Java installations cache cleared.
```

Step 6: Manage Project-Specific Java Versions

List Project-Specific Java Versions:
```
java_list(type = "project")
```
This function lists all Java versions symlinked in the current project directory.

Expected output:
```
<data.frame or vector of project-specific Java versions>
```
Clear Project-Specific Java Versions:
```
java_clear(type = "project")
```
This function clears all Java versions symlinked in the current project directory.

Expected output:
```
All Java symlinks in the project have been cleared.
```

Step 7: Check Java Version

Check Installed Java Version using Terminal Commands:
```
java_check_version_cmd()
```
This function checks the Java version using terminal commands and prints the Java version and path.

Expected output:
```
JAVA_HOME: <current_java_home>
Java path: <java_path>
Java version:
<java_version_details>
```

Check Java Version using rJava in a Separate R Session:

java_check_version_rjava("/path/to/installed/java")

This function checks the Java version using rJava in a separate R session.

Expected output:

With the current session's JAVA_HOME <java_version_details>
or
With the user-specified JAVA_HOME <java_version_details>