Online installer packages on all supported operating systems should provide "java" external tool (or "JRE" - let's discuss the exact name of the tool during the integration).
Thus, a user should be able to run a java-tool such as Trimmomatic out-of-the-box.
Use the following tool description:
"java" (JRE, Java Runtime Environment) is required to run several other external tools (e.g. FastQC and Trimmomatic).