Question
Answer and Explanation
To specify the Java version that SBT (Simple Build Tool) uses, you typically configure it using the `sbtopts` file. Here’s how you can do it:
1. Locate the `sbtopts` File:
- The `sbtopts` file is usually located in the `.sbt` directory in your user's home directory (`~/.sbt/sbtopts` on Unix-like systems or `C:\Users\YourUsername\.sbt\sbtopts` on Windows) . If the file does not exist, you can create it.
2. Set the Java Version:
- Inside the `sbtopts` file, you can specify JVM options, including the Java version. You usually do this using the `-J` prefix, followed by the specific Java option. To select a specific Java version you would use the `-J-XX:MaxPermSize=256m -J-Djava.version=1.8` format for example, or the `-J-Djava.version=11` format. You can also select specific Java location using `-J-Djava.home=/path/to/your/java_home`. For example, to use Java 11, your `sbtopts` file might look like this:
-J-Xmx2G
-J-Djava.version=11
- In this configuration: `-J-Xmx2G`: Sets the maximum heap size for the Java Virtual Machine (JVM) to 2 gigabytes (this option is often helpful in general, it's included as an example), the -J allows to pass options to underlying JVM. `-J-Djava.version=11`: Explicitly specifies that Java version 11 should be used. Note that setting `java.version` doesn't change the JRE being used, it will only change the version sbt thinks it is running on. The `-J-Djava.home` is a more appropriate option in order to set the JRE/JDK to be used.
3. Using the `JAVA_HOME` Environment Variable:
- Alternatively, you can set the `JAVA_HOME` environment variable to point to your desired Java installation path. SBT will typically use the JDK pointed to by `JAVA_HOME`, although the `sbtopts` takes precedence if specified.
- For example, on a Linux or macOS system, you might add the following to your `.bashrc` or `.zshrc` file:
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
- Then update your environment `source ~/.bashrc` (or `source ~/.zshrc`). Similarly you can set the same in the "Advanced system settings" on Windows for the relevant java version.
4. Using the `-java-home` Option
- It's also possible to set the java home directly from sbt by adding it to the sbtopts file, using `-java-home`, for example
-java-home /usr/lib/jvm/java-11-openjdk-amd64
5. Restart SBT:
- After modifying `sbtopts` or the `JAVA_HOME` variable, you may need to restart your SBT session for the changes to take effect.
Important Considerations:
- Make sure that the specified java version or path point to valid JDK/JRE installation. - Different SBT versions might have different compatibility for JDK/JRE versions. It's recommended to check SBTs official documentation for compatibility details.
By using either `sbtopts` or the `JAVA_HOME` environment variable, you can control the Java version SBT uses for compilation and running your projects. The `-java-home` or `-Djava.home` options are the preferred way to set java version, instead of `-Djava.version` which only affects how SBT understands java version.