diff --git a/aether-api/src/main/java/org/eclipse/aether/collection/UnsolvableVersionConflictException.java b/aether-api/src/main/java/org/eclipse/aether/collection/UnsolvableVersionConflictException.java
index 8ca8221a50f4603d87f730b8438812f66742da9d..b4c6ea5981b225d26425285b84b551ac58c00dee 100644
--- a/aether-api/src/main/java/org/eclipse/aether/collection/UnsolvableVersionConflictException.java
+++ b/aether-api/src/main/java/org/eclipse/aether/collection/UnsolvableVersionConflictException.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010, 2012 Sonatype, Inc.
+ * Copyright (c) 2010, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -30,9 +30,9 @@ public class UnsolvableVersionConflictException
 
     private final transient Collection<String> versions;
 
-    private final transient Collection<List<DependencyNode>> paths;
+    private final transient Collection<? extends List<? extends DependencyNode>> paths;
 
-    public UnsolvableVersionConflictException( Collection<List<DependencyNode>> paths )
+    public UnsolvableVersionConflictException( Collection<? extends List<? extends DependencyNode>> paths )
     {
         super( "Could not resolve version conflict among " + toPaths( paths ) );
         if ( paths == null )
@@ -44,7 +44,7 @@ public class UnsolvableVersionConflictException
         {
             this.paths = paths;
             this.versions = new LinkedHashSet<String>();
-            for ( List<DependencyNode> path : paths )
+            for ( List<? extends DependencyNode> path : paths )
             {
                 VersionConstraint constraint = path.get( path.size() - 1 ).getVersionConstraint();
                 if ( constraint != null && constraint.getRange() != null )
@@ -55,7 +55,7 @@ public class UnsolvableVersionConflictException
         }
     }
 
-    private static String toPaths( Collection<List<DependencyNode>> paths )
+    private static String toPaths( Collection<? extends List<? extends DependencyNode>> paths )
     {
         String result = "";
 
@@ -63,7 +63,7 @@ public class UnsolvableVersionConflictException
         {
             Collection<String> strings = new LinkedHashSet<String>();
 
-            for ( List<DependencyNode> path : paths )
+            for ( List<? extends DependencyNode> path : paths )
             {
                 strings.add( toPath( path ) );
             }
@@ -74,11 +74,11 @@ public class UnsolvableVersionConflictException
         return result;
     }
 
-    private static String toPath( List<DependencyNode> path )
+    private static String toPath( List<? extends DependencyNode> path )
     {
         StringBuilder buffer = new StringBuilder( 256 );
 
-        for ( Iterator<DependencyNode> it = path.iterator(); it.hasNext(); )
+        for ( Iterator<? extends DependencyNode> it = path.iterator(); it.hasNext(); )
         {
             DependencyNode node = it.next();
             if ( node.getDependency() == null )
@@ -110,7 +110,7 @@ public class UnsolvableVersionConflictException
      * 
      * @return The (read-only) paths leading to the conflicting dependencies, never {@code null}.
      */
-    public Collection<List<DependencyNode>> getPaths()
+    public Collection<? extends List<? extends DependencyNode>> getPaths()
     {
         return paths;
     }
diff --git a/aether-api/src/main/java/org/eclipse/aether/graph/DefaultDependencyNode.java b/aether-api/src/main/java/org/eclipse/aether/graph/DefaultDependencyNode.java
index e3be76f70e8050434b93a8d0bed03b6ed44c4dd4..ccecc73e7468bb3bf09165d30611182102f25299 100644
--- a/aether-api/src/main/java/org/eclipse/aether/graph/DefaultDependencyNode.java
+++ b/aether-api/src/main/java/org/eclipse/aether/graph/DefaultDependencyNode.java
@@ -35,9 +35,9 @@ public final class DefaultDependencyNode
 
     private Artifact artifact;
 
-    private List<Artifact> relocations;
+    private List<? extends Artifact> relocations;
 
-    private Collection<Artifact> aliases;
+    private Collection<? extends Artifact> aliases;
 
     private VersionConstraint versionConstraint;
 
@@ -102,7 +102,7 @@ public final class DefaultDependencyNode
         setRepositories( node.getRepositories() );
         setVersion( node.getVersion() );
         setVersionConstraint( node.getVersionConstraint() );
-        Map<Object, Object> data = node.getData();
+        Map<?, ?> data = node.getData();
         setData( data.isEmpty() ? null : new HashMap<Object, Object>( data ) );
     }
 
@@ -143,7 +143,7 @@ public final class DefaultDependencyNode
         this.artifact = dependency.getArtifact();
     }
 
-    public List<Artifact> getRelocations()
+    public List<? extends Artifact> getRelocations()
     {
         return relocations;
     }
@@ -153,7 +153,7 @@ public final class DefaultDependencyNode
      * 
      * @param relocations The sequence of relocations, may be {@code null}.
      */
-    public void setRelocations( List<Artifact> relocations )
+    public void setRelocations( List<? extends Artifact> relocations )
     {
         if ( relocations == null || relocations.isEmpty() )
         {
@@ -165,7 +165,7 @@ public final class DefaultDependencyNode
         }
     }
 
-    public Collection<Artifact> getAliases()
+    public Collection<? extends Artifact> getAliases()
     {
         return aliases;
     }
@@ -175,7 +175,7 @@ public final class DefaultDependencyNode
      * 
      * @param aliases The known aliases, may be {@code null}.
      */
-    public void setAliases( Collection<Artifact> aliases )
+    public void setAliases( Collection<? extends Artifact> aliases )
     {
         if ( aliases == null || aliases.isEmpty() )
         {
diff --git a/aether-api/src/main/java/org/eclipse/aether/graph/DependencyNode.java b/aether-api/src/main/java/org/eclipse/aether/graph/DependencyNode.java
index 867ec5000afd3706fb9861f3ff07802bc0df1ec0..4e345979f9104d09dbfb0602a6cdaa476af8b3f2 100644
--- a/aether-api/src/main/java/org/eclipse/aether/graph/DependencyNode.java
+++ b/aether-api/src/main/java/org/eclipse/aether/graph/DependencyNode.java
@@ -116,7 +116,7 @@ public interface DependencyNode
      * 
      * @return The (read-only) sequence of relocations, never {@code null}.
      */
-    List<Artifact> getRelocations();
+    List<? extends Artifact> getRelocations();
 
     /**
      * Gets the known aliases for this dependency's artifact. An alias can be used to mark a patched rebuild of some
@@ -125,7 +125,7 @@ public interface DependencyNode
      * 
      * @return The (read-only) set of known aliases, never {@code null}.
      */
-    Collection<Artifact> getAliases();
+    Collection<? extends Artifact> getAliases();
 
     /**
      * Gets the version constraint that was parsed from the dependency's version declaration.
@@ -194,7 +194,7 @@ public interface DependencyNode
      * 
      * @return The (read-only) key-value mappings, never {@code null}.
      */
-    Map<Object, Object> getData();
+    Map<?, ?> getData();
 
     /**
      * Sets the custom data associated with this dependency node.
diff --git a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDependencyCollector.java b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDependencyCollector.java
index 4d56fd9aecd76b6acfdf4912c3a4b8d41f67293c..477bd31df8f9d3db0a2c42747099f28d0e774f42 100644
--- a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDependencyCollector.java
+++ b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDependencyCollector.java
@@ -174,7 +174,7 @@ public class DefaultDependencyCollector
         DefaultDependencyNode node = null;
         if ( root != null )
         {
-            List<Version> versions;
+            List<? extends Version> versions;
             VersionRangeResult rangeResult;
             try
             {
@@ -405,7 +405,7 @@ public class DefaultDependencyCollector
 
                 boolean traverse = !noDescriptor && depTraverser.traverseDependency( dependency );
 
-                List<Version> versions;
+                List<? extends Version> versions;
                 VersionRangeResult rangeResult;
                 try
                 {
@@ -638,8 +638,8 @@ public class DefaultDependencyCollector
         return repositories;
     }
 
-    private List<Version> filterVersions( Dependency dependency, VersionRangeResult rangeResult,
-                                          VersionFilter verFilter, DefaultVersionFilterContext verContext )
+    private List<? extends Version> filterVersions( Dependency dependency, VersionRangeResult rangeResult,
+                                                    VersionFilter verFilter, DefaultVersionFilterContext verContext )
         throws VersionRangeResolutionException
     {
         if ( rangeResult.getVersions().isEmpty() )
@@ -648,7 +648,7 @@ public class DefaultDependencyCollector
                 + dependency.getArtifact() + " within specified range" );
         }
 
-        List<Version> versions;
+        List<? extends Version> versions;
         if ( verFilter != null && rangeResult.getVersionConstraint().getRange() != null )
         {
             verContext.set( dependency, rangeResult );
diff --git a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDeployer.java b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDeployer.java
index 60b1735be1a81e993326ec6a81b19457befe7cc3..6a1b6c1904de08b2e5c1e1c80e1c3601e2149776 100644
--- a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDeployer.java
+++ b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultDeployer.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010, 2012 Sonatype, Inc.
+ * Copyright (c) 2010, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -294,7 +294,7 @@ public class DefaultDeployer
 
         try
         {
-            List<MetadataGenerator> generators = getMetadataGenerators( session, request );
+            List<? extends MetadataGenerator> generators = getMetadataGenerators( session, request );
 
             List<ArtifactUpload> artifactUploads = new ArrayList<ArtifactUpload>();
             List<MetadataUpload> metadataUploads = new ArrayList<MetadataUpload>();
@@ -379,7 +379,8 @@ public class DefaultDeployer
         return result;
     }
 
-    private List<MetadataGenerator> getMetadataGenerators( RepositorySystemSession session, DeployRequest request )
+    private List<? extends MetadataGenerator> getMetadataGenerators( RepositorySystemSession session,
+                                                                     DeployRequest request )
     {
         List<MetadataGeneratorFactory> factories = Utils.sortMetadataGeneratorFactories( this.metadataFactories );
 
diff --git a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultInstaller.java b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultInstaller.java
index 81b521061297fc4643a3f0202f8279ac6311120b..d496bc07227455dfea82c4ece773bed589abe2b2 100644
--- a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultInstaller.java
+++ b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultInstaller.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010, 2011 Sonatype, Inc.
+ * Copyright (c) 2010, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -190,7 +190,7 @@ public class DefaultInstaller
 
         RequestTrace trace = RequestTrace.newChild( request.getTrace(), request );
 
-        List<MetadataGenerator> generators = getMetadataGenerators( session, request );
+        List<? extends MetadataGenerator> generators = getMetadataGenerators( session, request );
 
         List<Artifact> artifacts = new ArrayList<Artifact>( request.getArtifacts() );
 
@@ -245,7 +245,8 @@ public class DefaultInstaller
         return result;
     }
 
-    private List<MetadataGenerator> getMetadataGenerators( RepositorySystemSession session, InstallRequest request )
+    private List<? extends MetadataGenerator> getMetadataGenerators( RepositorySystemSession session,
+                                                                     InstallRequest request )
     {
         List<MetadataGeneratorFactory> factories = Utils.sortMetadataGeneratorFactories( this.metadataFactories );
 
diff --git a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/Utils.java b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/Utils.java
index d767eea076f845b54ff57e2ca57970fe110191e5..8d4e0760b4021d7d17d4ce26b81349756f1dff72 100644
--- a/aether-impl/src/main/java/org/eclipse/aether/internal/impl/Utils.java
+++ b/aether-impl/src/main/java/org/eclipse/aether/internal/impl/Utils.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010, 2012 Sonatype, Inc.
+ * Copyright (c) 2010, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -40,14 +40,15 @@ final class Utils
 
     };
 
-    public static List<MetadataGeneratorFactory> sortMetadataGeneratorFactories( Collection<MetadataGeneratorFactory> factories )
+    public static List<MetadataGeneratorFactory> sortMetadataGeneratorFactories( Collection<? extends MetadataGeneratorFactory> factories )
     {
         List<MetadataGeneratorFactory> result = new ArrayList<MetadataGeneratorFactory>( factories );
         Collections.sort( result, COMPARATOR );
         return result;
     }
 
-    public static List<Metadata> prepareMetadata( List<MetadataGenerator> generators, List<Artifact> artifacts )
+    public static List<Metadata> prepareMetadata( List<? extends MetadataGenerator> generators,
+                                                  List<? extends Artifact> artifacts )
     {
         List<Metadata> metadatas = new ArrayList<Metadata>();
 
@@ -59,7 +60,8 @@ final class Utils
         return metadatas;
     }
 
-    public static List<Metadata> finishMetadata( List<MetadataGenerator> generators, List<Artifact> artifacts )
+    public static List<Metadata> finishMetadata( List<? extends MetadataGenerator> generators,
+                                                 List<? extends Artifact> artifacts )
     {
         List<Metadata> metadatas = new ArrayList<Metadata>();
 
diff --git a/aether-util/src/main/java/org/eclipse/aether/util/graph/selector/AndDependencySelector.java b/aether-util/src/main/java/org/eclipse/aether/util/graph/selector/AndDependencySelector.java
index a77d33b604862621e2fff2593147b47cdda52646..33d710adf606190c59530cecec23e4906ee60b63 100644
--- a/aether-util/src/main/java/org/eclipse/aether/util/graph/selector/AndDependencySelector.java
+++ b/aether-util/src/main/java/org/eclipse/aether/util/graph/selector/AndDependencySelector.java
@@ -10,6 +10,7 @@
  *******************************************************************************/
 package org.eclipse.aether.util.graph.selector;
 
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashSet;
@@ -26,7 +27,7 @@ public final class AndDependencySelector
     implements DependencySelector
 {
 
-    private final Set<DependencySelector> selectors;
+    private final Set<? extends DependencySelector> selectors;
 
     private int hashCode;
 
@@ -39,8 +40,7 @@ public final class AndDependencySelector
     {
         if ( selectors != null && selectors.length > 0 )
         {
-            this.selectors = new LinkedHashSet<DependencySelector>();
-            Collections.addAll( this.selectors, selectors );
+            this.selectors = new LinkedHashSet<DependencySelector>( Arrays.asList( selectors ) );
         }
         else
         {
@@ -53,7 +53,7 @@ public final class AndDependencySelector
      * 
      * @param selectors The selectors to combine, may be {@code null}.
      */
-    public AndDependencySelector( Collection<DependencySelector> selectors )
+    public AndDependencySelector( Collection<? extends DependencySelector> selectors )
     {
         if ( selectors != null && !selectors.isEmpty() )
         {
diff --git a/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedRepositoryListener.java b/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedRepositoryListener.java
index 7dbade7e550624bbd068aa526fe6fa1cae000407..15b0503344100537e34000b73d1db923316bb0b0 100644
--- a/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedRepositoryListener.java
+++ b/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedRepositoryListener.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010, 2011 Sonatype, Inc.
+ * Copyright (c) 2010, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -69,7 +69,7 @@ public final class ChainedRepositoryListener
      * 
      * @param listeners The listeners to delegate to, may be {@code null} or empty.
      */
-    public ChainedRepositoryListener( Collection<RepositoryListener> listeners )
+    public ChainedRepositoryListener( Collection<? extends RepositoryListener> listeners )
     {
         add( listeners );
     }
@@ -79,7 +79,7 @@ public final class ChainedRepositoryListener
      * 
      * @param listeners The listeners to add, may be {@code null} or empty.
      */
-    public void add( Collection<RepositoryListener> listeners )
+    public void add( Collection<? extends RepositoryListener> listeners )
     {
         if ( listeners != null )
         {
diff --git a/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedTransferListener.java b/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedTransferListener.java
index d08a9e54c73775618f6179066fd12bbc78a3a331..e9d8df650ea3cb9745cf7a582b3179a29ae057e3 100644
--- a/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedTransferListener.java
+++ b/aether-util/src/main/java/org/eclipse/aether/util/listener/ChainedTransferListener.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2010, 2011 Sonatype, Inc.
+ * Copyright (c) 2010, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -70,7 +70,7 @@ public final class ChainedTransferListener
      * 
      * @param listeners The listeners to delegate to, may be {@code null} or empty.
      */
-    public ChainedTransferListener( Collection<TransferListener> listeners )
+    public ChainedTransferListener( Collection<? extends TransferListener> listeners )
     {
         add( listeners );
     }
@@ -80,7 +80,7 @@ public final class ChainedTransferListener
      * 
      * @param listeners The listeners to add, may be {@code null} or empty.
      */
-    public void add( Collection<TransferListener> listeners )
+    public void add( Collection<? extends TransferListener> listeners )
     {
         if ( listeners != null )
         {
diff --git a/aether-util/src/main/java/org/eclipse/aether/util/repository/ChainedAuthentication.java b/aether-util/src/main/java/org/eclipse/aether/util/repository/ChainedAuthentication.java
index ec7c694f08ebe78975b48f20db9c5571aafe9c14..96968a0e7af2353e5b2039ba0f9870290445159b 100644
--- a/aether-util/src/main/java/org/eclipse/aether/util/repository/ChainedAuthentication.java
+++ b/aether-util/src/main/java/org/eclipse/aether/util/repository/ChainedAuthentication.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2012 Sonatype, Inc.
+ * Copyright (c) 2012, 2013 Sonatype, Inc.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -40,7 +40,7 @@ final class ChainedAuthentication
         }
     }
 
-    public ChainedAuthentication( Collection<Authentication> authentications )
+    public ChainedAuthentication( Collection<? extends Authentication> authentications )
     {
         if ( authentications != null && !authentications.isEmpty() )
         {