diff --git a/ivy/src/main/scala/sbt/ConflictWarning.scala b/ivy/src/main/scala/sbt/ConflictWarning.scala
index 6e6b8a37d..082a478b6 100644
--- a/ivy/src/main/scala/sbt/ConflictWarning.scala
+++ b/ivy/src/main/scala/sbt/ConflictWarning.scala
@@ -33,7 +33,7 @@ object ConflictWarning {
   }
   private[this] def processCrossVersioned(config: ConflictWarning, report: UpdateReport, log: Logger) {
     val crossMismatches = crossVersionMismatches(report)
-    if (!crossMismatches.isEmpty) {
+    if (crossMismatches.nonEmpty) {
       val pre = s"Modules were resolved with conflicting cross-version suffixes in ${config.label}:\n   "
       val conflictMsgs =
         for (((org, rawName), fullNames) <- crossMismatches) yield {
diff --git a/ivy/src/main/scala/sbt/EvictionWarning.scala b/ivy/src/main/scala/sbt/EvictionWarning.scala
index 25ad9014b..cb786ca3f 100644
--- a/ivy/src/main/scala/sbt/EvictionWarning.scala
+++ b/ivy/src/main/scala/sbt/EvictionWarning.scala
@@ -93,7 +93,7 @@ object EvictionPair {
           }
         else ""
       r.module.revision + callers
-    }).headOption map { " -> " + _ } getOrElse ""
+    }) map { " -> " + _ } getOrElse ""
     Seq(s"\t* ${a.organization}:${a.name}:${revsStr}$winnerRev")
   }
 }
@@ -160,7 +160,7 @@ object EvictionWarning {
     pairs foreach {
       case p if isScalaArtifact(module, p.organization, p.name) =>
         (module.moduleSettings.ivyScala, p.winner) match {
-          case (Some(s), Some(winner)) if ((s.scalaFullVersion != winner.module.revision) && options.warnScalaVersionEviction) =>
+          case (Some(s), Some(winner)) if (s.scalaFullVersion != winner.module.revision) && options.warnScalaVersionEviction =>
             scalaEvictions += p
           case _ =>
         }
@@ -180,21 +180,21 @@ object EvictionWarning {
   implicit val evictionWarningLines: ShowLines[EvictionWarning] = ShowLines { a: EvictionWarning =>
     import ShowLines._
     val out: mutable.ListBuffer[String] = mutable.ListBuffer()
-    if (!a.scalaEvictions.isEmpty) {
+    if (a.scalaEvictions.nonEmpty) {
       out += "Scala version was updated by one of library dependencies:"
       out ++= (a.scalaEvictions flatMap { _.lines })
       out += "To force scalaVersion, add the following:"
       out += "\tivyScala := ivyScala.value map { _.copy(overrideScalaVersion = true) }"
     }
 
-    if (!a.directEvictions.isEmpty || !a.transitiveEvictions.isEmpty) {
+    if (a.directEvictions.nonEmpty || a.transitiveEvictions.nonEmpty) {
       out += "There may be incompatibilities among your library dependencies."
       out += "Here are some of the libraries that were evicted:"
       out ++= (a.directEvictions flatMap { _.lines })
       out ++= (a.transitiveEvictions flatMap { _.lines })
     }
 
-    if (!a.allEvictions.isEmpty && !a.reportedEvictions.isEmpty && !a.options.showCallers) {
+    if (a.allEvictions.nonEmpty && a.reportedEvictions.nonEmpty && !a.options.showCallers) {
       out += "Run 'evicted' to see detailed eviction warnings"
     }
 
diff --git a/ivy/src/main/scala/sbt/Ivy.scala b/ivy/src/main/scala/sbt/Ivy.scala
index c0e7d508a..8b3bfe5ec 100644
--- a/ivy/src/main/scala/sbt/Ivy.scala
+++ b/ivy/src/main/scala/sbt/Ivy.scala
@@ -19,7 +19,7 @@ import org.apache.ivy.core.cache.{ CacheMetadataOptions, DefaultRepositoryCacheM
 import org.apache.ivy.core.event.EventManager
 import org.apache.ivy.core.module.descriptor.{ Artifact => IArtifact, DefaultArtifact, DefaultDependencyArtifactDescriptor, MDArtifact }
 import org.apache.ivy.core.module.descriptor.{ DefaultDependencyDescriptor, DefaultModuleDescriptor, DependencyDescriptor, ModuleDescriptor, License }
-import org.apache.ivy.core.module.descriptor.{ OverrideDependencyDescriptorMediator }
+import org.apache.ivy.core.module.descriptor.OverrideDependencyDescriptorMediator
 import org.apache.ivy.core.module.id.{ ArtifactId, ModuleId, ModuleRevisionId }
 import org.apache.ivy.core.resolve.{ IvyNode, ResolveData, ResolvedModuleRevision, ResolveEngine }
 import org.apache.ivy.core.settings.IvySettings
@@ -496,7 +496,7 @@ private[sbt] object IvySbt {
   private def hasInfo(module: ModuleID, x: scala.xml.NodeSeq) =
     {
       val info = <g>{ x }</g> \ "info"
-      if (!info.isEmpty) {
+      if (info.nonEmpty) {
         def check(found: NodeSeq, expected: String, label: String) =
           if (found.isEmpty)
             sys.error("Missing " + label + " in inline Ivy XML.")
@@ -508,7 +508,7 @@ private[sbt] object IvySbt {
         check(info \ "@module", module.name, "name")
         check(info \ "@revision", module.revision, "version")
       }
-      !info.isEmpty
+      info.nonEmpty
     }
   /** Parses the given in-memory Ivy file 'xml', using the existing 'moduleID' and specifying the given 'defaultConfiguration'. */
   private def parseIvyXML(settings: IvySettings, xml: scala.xml.NodeSeq, moduleID: DefaultModuleDescriptor, defaultConfiguration: String, validate: Boolean): CustomXmlParser.CustomParser =
@@ -582,7 +582,7 @@ private[sbt] object IvySbt {
       for (artifact <- dependency.explicitArtifacts) {
         import artifact.{ name, classifier, `type`, extension, url }
         val extraMap = extra(artifact)
-        val ivyArtifact = new DefaultDependencyArtifactDescriptor(dependencyDescriptor, name, `type`, extension, url.getOrElse(null), extraMap)
+        val ivyArtifact = new DefaultDependencyArtifactDescriptor(dependencyDescriptor, name, `type`, extension, url.orNull, extraMap)
         copyConfigurations(artifact, ivyArtifact.addConfiguration)
         for (conf <- dependencyDescriptor.getModuleConfigurations)
           dependencyDescriptor.addDependencyArtifact(conf, ivyArtifact)
diff --git a/ivy/src/main/scala/sbt/IvyActions.scala b/ivy/src/main/scala/sbt/IvyActions.scala
index a6754b138..39af5bee9 100644
--- a/ivy/src/main/scala/sbt/IvyActions.scala
+++ b/ivy/src/main/scala/sbt/IvyActions.scala
@@ -226,7 +226,7 @@ object IvyActions {
     {
       import config.{ configuration => c, module => mod, _ }
       import mod.{ configurations => confs, _ }
-      assert(!classifiers.isEmpty, "classifiers cannot be empty")
+      assert(classifiers.nonEmpty, "classifiers cannot be empty")
       val baseModules = modules map { m => restrictedCopy(m, true) }
       val deps = baseModules.distinct flatMap classifiedArtifacts(classifiers, exclude)
       val base = restrictedCopy(id, true).copy(name = id.name + classifiers.mkString("$", "_", ""))
@@ -375,16 +375,16 @@ object UnresolvedWarning {
       case _ => ""
     }
   implicit val unresolvedWarningLines: ShowLines[UnresolvedWarning] = ShowLines { a =>
-    val withExtra = a.resolveException.failed.filter(!_.extraDependencyAttributes.isEmpty)
+    val withExtra = a.resolveException.failed.filter(_.extraDependencyAttributes.nonEmpty)
     val buffer = mutable.ListBuffer[String]()
-    if (!withExtra.isEmpty) {
+    if (withExtra.nonEmpty) {
       buffer += "\n\tNote: Some unresolved dependencies have extra attributes.  Check that these dependencies exist with the requested attributes."
       withExtra foreach { id => buffer += "\t\t" + id }
     }
-    if (!a.failedPaths.isEmpty) {
+    if (a.failedPaths.nonEmpty) {
       buffer += "\n\tNote: Unresolved dependencies path:"
       a.failedPaths foreach { path =>
-        if (!path.isEmpty) {
+        if (path.nonEmpty) {
           val head = path.head
           buffer += "\t\t" + head._1.toString + sourcePosStr(head._2)
           path.tail foreach {
diff --git a/ivy/src/main/scala/sbt/MakePom.scala b/ivy/src/main/scala/sbt/MakePom.scala
index eba0cd94d..904be0c8c 100644
--- a/ivy/src/main/scala/sbt/MakePom.scala
+++ b/ivy/src/main/scala/sbt/MakePom.scala
@@ -258,7 +258,7 @@ class MakePom(val log: Logger) {
   @deprecated("No longer used and will be removed.", "0.12.1")
   def classifier(dependency: DependencyDescriptor, includeTypes: Set[String]): NodeSeq =
     {
-      val jarDep = dependency.getAllDependencyArtifacts.filter(d => includeTypes(d.getType)).headOption
+      val jarDep = dependency.getAllDependencyArtifacts.find(d => includeTypes(d.getType))
       jarDep match {
         case Some(a) => classifierElem(artifactClassifier(a))
         case None    => NodeSeq.Empty
@@ -298,15 +298,15 @@ class MakePom(val log: Logger) {
       val (opt, notOptional) = confs.partition(_ == Optional.name)
       val defaultNotOptional = Configurations.defaultMavenConfigurations.find(notOptional contains _.name)
       val scope = defaultNotOptional.map(_.name)
-      (scope, !opt.isEmpty)
+      (scope, opt.nonEmpty)
     }
 
   def exclusions(dependency: DependencyDescriptor): NodeSeq =
     {
       val excl = dependency.getExcludeRules(dependency.getModuleConfigurations)
       val (warns, excls) = IvyUtil.separate(excl.map(makeExclusion))
-      if (!warns.isEmpty) log.warn(warns.mkString(IO.Newline))
-      if (!excls.isEmpty) <exclusions>{ excls }</exclusions>
+      if (warns.nonEmpty) log.warn(warns.mkString(IO.Newline))
+      if (excls.nonEmpty) <exclusions>{ excls }</exclusions>
       else NodeSeq.Empty
     }
   def makeExclusion(exclRule: ExcludeRule): Either[String, NodeSeq] =
diff --git a/ivy/src/main/scala/sbt/ResolutionCache.scala b/ivy/src/main/scala/sbt/ResolutionCache.scala
index 41721a784..0fd7a0a06 100644
--- a/ivy/src/main/scala/sbt/ResolutionCache.scala
+++ b/ivy/src/main/scala/sbt/ResolutionCache.scala
@@ -52,7 +52,7 @@ private[sbt] final class ResolutionCache(base: File, settings: IvySettings) exte
       throw new IllegalStateException("Ivy file not found in cache for " + mrid + "!")
     }
 
-    return XmlModuleDescriptorParser.getInstance().parseDescriptor(settings, ivyFile.toURI().toURL(), false)
+    XmlModuleDescriptorParser.getInstance().parseDescriptor(settings, ivyFile.toURI.toURL, false)
   }
 
   def saveResolvedModuleDescriptor(md: ModuleDescriptor): Unit = {
diff --git a/ivy/src/main/scala/sbt/VersionNumber.scala b/ivy/src/main/scala/sbt/VersionNumber.scala
index 7db8c8fef..182d44edc 100644
--- a/ivy/src/main/scala/sbt/VersionNumber.scala
+++ b/ivy/src/main/scala/sbt/VersionNumber.scala
@@ -97,7 +97,7 @@ object VersionNumber {
             case (0L, _, _, _, 0L, _, _, _) =>
               // Major version zero (0.y.z) is for initial development. Anything may change at any time. The public API should not be considered stable.
               equalsIgnoreExtra(v1, v2)
-            case (_, 0, 0, ts1, _, 0, 0, ts2) if (!ts1.isEmpty) || (!ts2.isEmpty) =>
+            case (_, 0, 0, ts1, _, 0, 0, ts2) if ts1.nonEmpty || ts2.nonEmpty =>
               // A pre-release version MAY be denoted by appending a hyphen and a series of dot separated identifiers
               equalsIgnoreExtra(v1, v2)
             case (x1, _, _, _, x2, _, _, _) =>
@@ -125,7 +125,7 @@ object VersionNumber {
       (v1, v2) match {
         case (v1, v2) if (v1.size >= 3) && (v2.size >= 3) => // A normal version number MUST take the form X.Y.Z
           (v1._1.get, v1._2.get, v1._3.get, v1.tags, v2._1.get, v2._2.get, v2._3.get, v2.tags) match {
-            case (x1, y1, 0, ts1, x2, y2, 0, ts2) if (!ts1.isEmpty) || (!ts2.isEmpty) =>
+            case (x1, y1, 0, ts1, x2, y2, 0, ts2) if ts1.nonEmpty || ts2.nonEmpty =>
               // A pre-release version MAY be denoted by appending a hyphen and a series of dot separated identifiers
               equalsIgnoreExtra(v1, v2)
             case (x1, y1, _, _, x2, y2, _, _) =>
diff --git a/ivy/src/main/scala/sbt/ivyint/CachedResolutionResolveEngine.scala b/ivy/src/main/scala/sbt/ivyint/CachedResolutionResolveEngine.scala
index 32442167a..76b576412 100644
--- a/ivy/src/main/scala/sbt/ivyint/CachedResolutionResolveEngine.scala
+++ b/ivy/src/main/scala/sbt/ivyint/CachedResolutionResolveEngine.scala
@@ -67,7 +67,7 @@ private[sbt] class CachedResolutionResolveCache() {
             // direct dependencies of an internal dependency
             val directs0 = directDependencies(internal)
             val directs = directs0 filter { dd =>
-              allConfigurations exists { conf => !dd.getDependencyConfigurations(conf).isEmpty }
+              allConfigurations exists { conf => dd.getDependencyConfigurations(conf).nonEmpty }
             }
             directs flatMap { dd => expandInternalDeps(dd, next) }
           case _ =>
diff --git a/ivy/src/main/scala/sbt/ivyint/ErrorMessageAuthenticator.scala b/ivy/src/main/scala/sbt/ivyint/ErrorMessageAuthenticator.scala
index e59e36e34..bb5996834 100644
--- a/ivy/src/main/scala/sbt/ivyint/ErrorMessageAuthenticator.scala
+++ b/ivy/src/main/scala/sbt/ivyint/ErrorMessageAuthenticator.scala
@@ -92,7 +92,7 @@ private[sbt] final class ErrorMessageAuthenticator(original: Option[Authenticato
       // TODO - levenshtein distance "did you mean" message.
       Message.error(s"Unable to find credentials for [${getRequestingPrompt} @ ${host}].")
       val configuredRealms = IvyCredentialsLookup.realmsForHost.getOrElse(host, Set.empty)
-      if (!configuredRealms.isEmpty) {
+      if (configuredRealms.nonEmpty) {
         Message.error(s"  Is one of these realms mispelled for host [${host}]:")
         configuredRealms foreach { realm =>
           Message.error(s"  * ${realm}")
@@ -116,7 +116,7 @@ private[sbt] final class ErrorMessageAuthenticator(original: Option[Authenticato
         getRequestingScheme))
       finally Authenticator.setDefault(this)
     }
-    originalAuthentication.getOrElse(null)
+    originalAuthentication.orNull
   }
 
   /**