On windows machine, adding .bat worked for me.

String cmd = "allure.bat generate allure-results -o E:\project\target\reports\loginReport --clean"; Process process = Runtime.getRuntime().exec(cmd); process.waitFor()

Be sure to have specified the bin directory of allure in your PATH sys env variables (where the .bat file is located). You can locate it typing in cmd: "where allure.bat"

For me path was C:\Program Files\allure-2.30.0\bin