[MNG-6855] Simplify code - computeIfAbsent()

maven-compat/src/main/java/org/apache/maven/repository/legacy/LegacyRepositorySystem.java

@@ -396,13 +396,7 @@ public class LegacyRepositorySystem
         {
             String key = repository.getId();
 
-            List<ArtifactRepository> aliasedRepos = reposByKey.get( key );
+            List<ArtifactRepository> aliasedRepos = reposByKey.computeIfAbsent( key, k -> new ArrayList<>() );
-
-            if ( aliasedRepos == null )
-            {
-                aliasedRepos = new ArrayList<>();
-                reposByKey.put( key, aliasedRepos );
-            }
 
             aliasedRepos.add( repository );
         }

maven-compat/src/main/java/org/apache/maven/repository/metadata/MetadataGraph.java

@@ -331,24 +331,14 @@ public class MetadataGraph
         vFrom.setCompareVersion( versionedVertices );
         vFrom.setCompareScope( scopedVertices );
 
-        List<MetadataGraphEdge> exList = excidentEdges.get( vFrom );
+        List<MetadataGraphEdge> exList = excidentEdges.computeIfAbsent( vFrom, k -> new ArrayList<>() );
-        if ( exList == null )
-        {
-            exList = new ArrayList<>();
-            excidentEdges.put( vFrom, exList );
-        }
 
         if ( !exList.contains( e ) )
         {
             exList.add( e );
         }
 
-        List<MetadataGraphEdge> inList = incidentEdges.get( vTo );
+        List<MetadataGraphEdge> inList = incidentEdges.computeIfAbsent( vTo, k -> new ArrayList<>() );
-        if ( inList == null )
-        {
-            inList = new ArrayList<>();
-            incidentEdges.put( vTo, inList );
-        }
 
         if ( !inList.contains( e ) )
         {

maven-core/src/main/java/org/apache/maven/ReactorReader.java

@@ -73,13 +73,7 @@ class ReactorReader
         {
             String key = ArtifactUtils.versionlessKey( project.getGroupId(), project.getArtifactId() );
 
-            List<MavenProject> projects = projectsByGA.get( key );
+            List<MavenProject> projects = projectsByGA.computeIfAbsent( key, k -> new ArrayList<>( 1 ) );
-
-            if ( projects == null )
-            {
-                projects = new ArrayList<>( 1 );
-                projectsByGA.put( key, projects );
-            }
 
             projects.add( project );
         }

maven-core/src/main/java/org/apache/maven/bridge/MavenRepositorySystem.java

@@ -621,13 +621,7 @@ public class MavenRepositorySystem
         {
             String key = repository.getId();
 
-            List<ArtifactRepository> aliasedRepos = reposByKey.get( key );
+            List<ArtifactRepository> aliasedRepos = reposByKey.computeIfAbsent( key, k -> new ArrayList<>() );
-
-            if ( aliasedRepos == null )
-            {
-                aliasedRepos = new ArrayList<>();
-                reposByKey.put( key, aliasedRepos );
-            }
 
             aliasedRepos.add( repository );
         }

maven-core/src/main/java/org/apache/maven/execution/ReactorManager.java

@@ -70,23 +70,10 @@ public class ReactorManager
 
     public Map getPluginContext( PluginDescriptor plugin, MavenProject project )
     {
-        Map<String, Map> pluginContextsByKey = pluginContextsByProjectAndPluginKey.get( project.getId() );
+        Map<String, Map> pluginContextsByKey =
+            pluginContextsByProjectAndPluginKey.computeIfAbsent( project.getId(), k -> new HashMap<>() );
 
-        if ( pluginContextsByKey == null )
+        return pluginContextsByKey.computeIfAbsent( plugin.getPluginLookupKey(), k -> new HashMap<>() );
-        {
-            pluginContextsByKey = new HashMap<>();
-            pluginContextsByProjectAndPluginKey.put( project.getId(), pluginContextsByKey );
-        }
-
-        Map pluginContext = pluginContextsByKey.get( plugin.getPluginLookupKey() );
-
-        if ( pluginContext == null )
-        {
-            pluginContext = new HashMap<>();
-            pluginContextsByKey.put( plugin.getPluginLookupKey(), pluginContext );
-        }
-
-        return pluginContext;
     }
 
     public void setFailureBehavior( String failureBehavior )

maven-core/src/main/java/org/apache/maven/lifecycle/internal/DefaultLifecycleMappingDelegate.java

@@ -149,13 +149,7 @@ public class DefaultLifecycleMappingDelegate
     private void addMojoExecution( Map<Integer, List<MojoExecution>> phaseBindings, MojoExecution mojoExecution,
                                    int priority )
     {
-        List<MojoExecution> mojoExecutions = phaseBindings.get( priority );
+        List<MojoExecution> mojoExecutions = phaseBindings.computeIfAbsent( priority, k -> new ArrayList<>() );
-
-        if ( mojoExecutions == null )
-        {
-            mojoExecutions = new ArrayList<>();
-            phaseBindings.put( priority, mojoExecutions );
-        }
 
         mojoExecutions.add( mojoExecution );
     }

maven-core/src/main/java/org/apache/maven/project/ProjectSorter.java

@@ -99,12 +99,8 @@ public class ProjectSorter
 
             String projectKey = ArtifactUtils.versionlessKey( project.getGroupId(), project.getArtifactId() );
 
-            Map<String, Vertex> vertices = vertexMap.get( projectKey );
+            Map<String, Vertex> vertices = vertexMap.computeIfAbsent( projectKey, k -> new HashMap<>( 2, 1 ) );
-            if ( vertices == null )
+
-            {
-                vertices = new HashMap<>( 2, 1 );
-                vertexMap.put( projectKey, vertices );
-            }
             vertices.put( project.getVersion(), dag.addVertex( projectId ) );
         }
 

maven-model-builder/src/main/java/org/apache/maven/model/building/DefaultModelBuilder.java

@@ -708,10 +708,7 @@ public class DefaultModelBuilder
                     for ( Plugin plugin : mgmt.getPlugins() )
                     {
                         String key = plugin.getKey();
-                        if ( managedVersions.get( key ) == null )
+                        managedVersions.computeIfAbsent( key, k -> plugin.getVersion() );
-                        {
-                            managedVersions.put( key, plugin.getVersion() );
-                        }
                     }
                 }
             }