Added a jarOfObject method to get the JAR of the class that an object

belongs to, which seems like a more common case.

core/src/main/scala/spark/SparkContext.scala

@@ -356,21 +356,23 @@ object SparkContext {
 
   // Find the JAR from which a given class was loaded, to make it easy for users to pass
   // their JARs to SparkContext
-  def jarOfClass[T: ClassManifest]: Option[String] = {
-    val cls = classManifest[T].erasure
+  def jarOfClass(cls: Class[_]): Seq[String] = {
     val uri = cls.getResource("/" + cls.getName.replace('.', '/') + ".class")
     if (uri != null) {
       val uriStr = uri.toString
       if (uriStr.startsWith("jar:file:")) {
         // URI will be of the form "jar:file:/path/foo.jar!/package/cls.class", so pull out the /path/foo.jar
-        Some(uriStr.substring("jar:file:".length, uriStr.indexOf('!')))
+        List(uriStr.substring("jar:file:".length, uriStr.indexOf('!')))
       } else {
-        None
+        Nil
       }
     } else {
-      None
+      Nil
     }
   }
+ 
+  // Find the JAR that contains the class of a particular object
+  def jarOfObject(obj: AnyRef): Seq[String] = jarOfClass(obj.getClass)
 }