Feedback.

Author: Marcelo Vanzin

core/src/main/scala/org/apache/spark/deploy/SparkSubmitArguments.scala

@@ -282,7 +282,7 @@ private[deploy] class SparkSubmitArguments(args: Seq[String], env: Map[String, S
     if (master.startsWith("yarn")) {
       val hasHadoopEnv = env.contains("HADOOP_CONF_DIR") || env.contains("YARN_CONF_DIR")
       if (!hasHadoopEnv && !Utils.isTesting) {
-        throw new Exception(s"When running with master '$master' " +
+        error(s"When running with master '$master' " +
           "either HADOOP_CONF_DIR or YARN_CONF_DIR must be set in the environment.")
       }
     }

launcher/src/main/java/org/apache/spark/launcher/SparkSubmitCommandBuilder.java

@@ -120,7 +120,7 @@ class SparkSubmitCommandBuilder extends AbstractCommandBuilder {
     this.parsedArgs = new ArrayList<>();
     boolean isExample = false;
     List<String> submitArgs = args;
-    this.userArgs = null;
+    this.userArgs = Collections.emptyList();
 
     if (args.size() > 0) {
       switch (args.get(0)) {
@@ -170,7 +170,7 @@ List<String> buildSparkSubmitArgs() {
 
     // If the user args array is not empty, we need to parse it to detect exactly what
     // the user is trying to run, so that checks below are correct.
-    if (userArgs != null && !userArgs.isEmpty()) {
+    if (!userArgs.isEmpty()) {
       parser.parse(userArgs);
       isStartingApp = parser.isAppResourceReq;
     }
@@ -419,7 +419,7 @@ private List<String> findExamplesJars() {
   private class OptionParser extends SparkSubmitOptionParser {
 
     boolean isAppResourceReq = true;
-    boolean errorOnUnknownArgs;
+    private final boolean errorOnUnknownArgs;
 
     OptionParser(boolean errorOnUnknownArgs) {
       this.errorOnUnknownArgs = errorOnUnknownArgs;