DesiredCapabilities dc = DesiredCapabilities.firefox();
dc.setCapability("browserName", DesiredCapabilities.firefox().getBrowserName());
dc.setCapability("browserVersion", "");
dc.setCapability("platformName", "WINDOWS");
dc.setCapability("firefox_binary", "C:\Program Files\Mozilla Firefox\firefox.exe");
dc.setCapability("acceptInsecureCerts", true);
dc.setCapability("marionette", true);

System.out.println("BrowserName : " + dc.getCapability("browserName"));

driver = new FirefoxDriver(dc);

org.openqa.selenium.InvalidArgumentException: browserName was not a boolean
Build info: version: '3.4.0', revision: 'unknown', time: 'unknown'
System info: host: '<ComputerName>', ip: '<IpAddress>', os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.8.0_121'
Driver info: driver.version: FirefoxDriver
remote stacktrace: stack backtrace:
   0:   0x47f1a6 - <no info>
   1:   0x437327 - <no info>
   2:   0x42bd8c - <no info>
   3:   0x437ded - <no info>
   4:   0x41a7b3 - <no info>
   5:   0x40570c - <no info>
   6:   0x692906 - <no info>
   7:   0x413838 - <no info>
   8:   0x68d401 - <no info>
   9: 0x7573336a - BaseThreadInitThunk
  10: 0x774b9902 - RtlInitializeExceptionChain

gecko-dev-masterthird_partyrustwebdriversrccapabilities.rs

for (key, value) in capabilities.iter() {
        match &**key {
            "acceptInsecureCerts" => if !value.is_boolean() {
                    return Err(WebDriverError::new(ErrorStatus::InvalidArgument,
                                                   "acceptInsecureCerts was not a boolean"))
                },
            x @ "browserName" |
            x @ "browserVersion" |
            x @ "platformName" => if !value.is_string() {
                    return Err(WebDriverError::new(ErrorStatus::InvalidArgument,
                                                   format!("{} was not a boolean", x)))
                },

dc.setCapability("browserName", "firefox");

System.setProperty("webdriver.gecko.driver", "C:\Utility\BrowserDrivers\geckodriver.exe");
DesiredCapabilities dc = DesiredCapabilities.firefox();
dc.setCapability("browserName", DesiredCapabilities.firefox().getBrowserName());
dc.setCapability("browserVersion", "");
dc.setCapability("platformName", "WINDOWS");
dc.setCapability("firefox_binary", "C:\Program Files\Mozilla Firefox\firefox.exe");
dc.setCapability("acceptInsecureCerts", true);
dc.setCapability("marionette", true);

System.out.println("BrowserName : " + dc.getCapability("browserName"));

WebDriver driver = new FirefoxDriver(dc);

Exception in thread "main" org.openqa.selenium.SessionNotCreatedException: Unable to find a matching set of capabilities
Build info: version: '3.4.0', revision: 'unknown', time: 'unknown'
System info: host: 'SmackMe', ip: '1.1.1.1', os.name: 'Windows 8', os.arch: 'amd64', os.version: '6.2', java.version: '1.8.0_77'
Driver info: driver.version: FirefoxDriver
remote stacktrace: stack backtrace:
   0:           0x489f6f - <no info>
   1:           0x48ad59 - <no info>
   2:           0x43c325 - <no info>
   3:           0x443f9a - <no info>
   4:           0x41ddb1 - <no info>
   5:           0x4091c7 - <no info>
   6:           0x6bc939 - <no info>
   7:           0x415a19 - <no info>
   8:           0x6b6e43 - <no info>
   9:      0x7f94d8a1842 - BaseThreadInitThunk

at demo.Q44440580_browsername_not_boolean.main(Q44440580_browsername_not_boolean.java:24)

WebDriver driver = new FirefoxDriver(dc);

<dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.0</version>
</dependency>