I believe you need to download and install Java first. After that .bat should run normally.
Please follow instructions from GitHub project page:
https://github.com/semuxproject/semux1. Download and install Java SE Runtime Environment 8.
2. Download the Latest Release and unpack it to a desired directory.
3. Run semux.bat if you're on Windows; or run ./semux.sh if you're on Linux or macOS. Be sure that your system date and time is properly synchronized. To run in command line mode, add --cli as a parameter.
4. (Windows user) You may also need to install Microsoft Visual C++ 2010 Redistributable Package.