Make required parameters actually be required.

Author: shs96c

java/client/src/org/openqa/selenium/firefox/FirefoxDriver.java

@@ -33,6 +33,7 @@
 import org.openqa.selenium.remote.service.DriverCommandExecutor;
 import org.openqa.selenium.remote.service.DriverService;
 
+import java.util.Objects;
 import java.util.Set;
 import java.util.logging.Logger;
 
@@ -100,11 +101,13 @@ public FirefoxDriver() {
   }
 
   public FirefoxDriver(Capabilities desiredCapabilities) {
-    this(new FirefoxOptions(desiredCapabilities));
+    this(new FirefoxOptions(Objects.requireNonNull(desiredCapabilities, "No capabilities seen")));
   }
 
   public FirefoxDriver(GeckoDriverService service, Capabilities desiredCapabilities) {
-    this(service, new FirefoxOptions(desiredCapabilities));
+    this(
+        Objects.requireNonNull(service, "No geckodriver service provided"),
+        new FirefoxOptions(desiredCapabilities));
   }
 
   public FirefoxDriver(FirefoxOptions options) {
@@ -116,6 +119,7 @@ public FirefoxDriver(GeckoDriverService service, FirefoxOptions options) {
   }
 
   private static CommandExecutor toExecutor(FirefoxOptions options) {
+    Objects.requireNonNull(options, "No options to construct executor from");
     DriverService.Builder<?, ?> builder;
 
     if (options.isLegacy()) {

java/client/src/org/openqa/selenium/remote/service/DriverCommandExecutor.java

@@ -29,6 +29,7 @@
 import java.io.IOException;
 import java.net.ConnectException;
 import java.util.Map;
+import java.util.Objects;
 
 /**
  * A specialized {@link HttpCommandExecutor} that will use a {@link DriverService} that lives
@@ -46,7 +47,7 @@ public class DriverCommandExecutor extends HttpCommandExecutor {
    * @param service The DriverService to send commands to.
    */
   public DriverCommandExecutor(DriverService service) {
-    super(service.getUrl());
+    super(Objects.requireNonNull(service.getUrl(), "DriverService is required"));
     this.service = service;
   }