面对壁虎错误

Question

每当我尝试调用壁虎时，都会向我显示这种错误。我不知道该怎么做。

at org.openqa.selenium.remote.service.DriverService$Builder.build(DriverService.java:346)
    at org.openqa.selenium.firefox.FirefoxDriver.toExecutor(FirefoxDriver.java:168)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:125)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:103)
    at introduction.Testcase2.main(Testcase2.java:25)

ff版本61.0.2和geckodriver v.0.21.0