Make LaunchManager's IResourceDeltaVisitors more light weight

1. Implement the IResourceDeltaVisitor in LaunchManager as lambda's
instead of nested classes.
2. Defer obtaining a delta's resource as long as possible and instead
only on the full-path of the delta.

Previously the resource of each delta was obtained without real need,
which lead to potentially unnecessary object creation.

Author: HannesWell

debug/org.eclipse.debug.core/core/org/eclipse/debug/internal/core/LaunchManager.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2022 IBM Corporation and others.
+ * Copyright (c) 2000, 2024 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -38,7 +38,6 @@
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -307,79 +306,6 @@ public void run() throws Exception {
 		}
 	}
 
-	/**
-	 * Visitor for handling a resource begin deleted, and the need to check mapped configurations
-	 * for auto-deletion
-	 * @since 3.4
-	 */
-	class MappedResourceVisitor implements IResourceDeltaVisitor {
-
-		@Override
-		public boolean visit(IResourceDelta delta) throws CoreException {
-			if (0 != (delta.getFlags() & IResourceDelta.OPEN)) {
-				return false;
-			}
-			if(delta.getKind() == IResourceDelta.REMOVED && delta.getFlags() != IResourceDelta.MOVED_TO) {
-				ArrayList<ILaunchConfiguration> configs = collectAssociatedLaunches(delta.getResource());
-				for (ILaunchConfiguration config : configs) {
-					try {
-						config.delete();
-					} catch (CoreException e) {
-						DebugPlugin.log(e.getStatus());
-					}
-				}
-				return false;
-			}
-			return true;
-		}
-	}
-
-	/**
-	 * Visitor for handling resource deltas.
-	 */
-	class LaunchManagerVisitor implements IResourceDeltaVisitor {
-
-		@Override
-		public boolean visit(IResourceDelta delta) {
-			if (delta == null) {
-				return false;
-			}
-			if (0 != (delta.getFlags() & IResourceDelta.OPEN)) {
-				if (delta.getResource() instanceof IProject) {
-					IProject project = (IProject)delta.getResource();
-					if (project.isOpen()) {
-						LaunchManager.this.projectOpened(project);
-					} else {
-						LaunchManager.this.projectClosed(project);
-					}
-				}
-				return false;
-			}
-			IResource resource = delta.getResource();
-			if (resource instanceof IFile) {
-				IFile file = (IFile)resource;
-				if (ILaunchConfiguration.LAUNCH_CONFIGURATION_FILE_EXTENSION.equals(file.getFileExtension()) || ILaunchConfiguration.LAUNCH_CONFIGURATION_PROTOTYPE_FILE_EXTENSION.equals(file.getFileExtension())) {
-					ILaunchConfiguration handle = new LaunchConfiguration(file);
-					switch (delta.getKind()) {
-						case IResourceDelta.ADDED :
-							LaunchManager.this.launchConfigurationAdded(handle);
-							break;
-						case IResourceDelta.REMOVED :
-							LaunchManager.this.launchConfigurationDeleted(handle);
-							break;
-						case IResourceDelta.CHANGED :
-							LaunchManager.this.launchConfigurationChanged(handle);
-							break;
-						default:
-							break;
-					}
-				}
-				return false;
-			}
-			return true;
-		}
-	}
-
 	/**
 	 * Notifies a launch listener (single launch) in a safe runnable to handle
 	 * exceptions.
@@ -631,7 +557,42 @@ public static String serializeDocument(Document doc, String lineDelimiter) throw
 	 * Visitor used to process resource deltas,
 	 * to update launch configuration index.
 	 */
-	private LaunchManagerVisitor fgVisitor;
+	private final IResourceDeltaVisitor fgVisitor = delta -> {
+		if (delta == null) {
+			return false;
+		}
+		if (0 != (delta.getFlags() & IResourceDelta.OPEN)) {
+			if (delta.getFullPath().segmentCount() == 1 && delta.getResource() instanceof IProject project) {
+				if (project.isOpen()) {
+					LaunchManager.this.projectOpened(project);
+				} else {
+					LaunchManager.this.projectClosed(project);
+				}
+			}
+			return false;
+		}
+		String fileExtension = delta.getFullPath().getFileExtension();
+		if (ILaunchConfiguration.LAUNCH_CONFIGURATION_FILE_EXTENSION.equals(fileExtension) || ILaunchConfiguration.LAUNCH_CONFIGURATION_PROTOTYPE_FILE_EXTENSION.equals(fileExtension)) {
+			if (delta.getResource() instanceof IFile file) {
+				ILaunchConfiguration handle = new LaunchConfiguration(file);
+				switch (delta.getKind()) {
+					case IResourceDelta.ADDED:
+						LaunchManager.this.launchConfigurationAdded(handle);
+						break;
+					case IResourceDelta.REMOVED:
+						LaunchManager.this.launchConfigurationDeleted(handle);
+						break;
+					case IResourceDelta.CHANGED:
+						LaunchManager.this.launchConfigurationChanged(handle);
+						break;
+					default:
+						break;
+				}
+			}
+			return false;
+		}
+		return true;
+	};
 
 	/**
 	 * Visitor used to process a deleted resource,
@@ -640,7 +601,23 @@ public static String serializeDocument(Document doc, String lineDelimiter) throw
 	 *
 	 * @since 3.4
 	 */
-	private MappedResourceVisitor fgMRVisitor;
+	private final IResourceDeltaVisitor fgMRVisitor = delta -> {
+		if (0 != (delta.getFlags() & IResourceDelta.OPEN)) {
+			return false;
+		}
+		if (delta.getKind() == IResourceDelta.REMOVED && delta.getFlags() != IResourceDelta.MOVED_TO) {
+			List<ILaunchConfiguration> configs = collectAssociatedLaunches(delta.getResource());
+			for (ILaunchConfiguration config : configs) {
+				try {
+					config.delete();
+				} catch (CoreException e) {
+					DebugPlugin.log(e.getStatus());
+				}
+			}
+			return false;
+		}
+		return true;
+	};
 
 	/**
 	 * Whether this manager is listening for resource change events
@@ -1129,31 +1106,6 @@ public IDebugTarget[] getDebugTargets() {
 		}
 	}
 
-	/**
-	 * Returns the resource delta visitor for the launch manager.
-	 *
-	 * @return the resource delta visitor for the launch manager
-	 */
-	private LaunchManagerVisitor getDeltaVisitor() {
-		if (fgVisitor == null) {
-			fgVisitor= new LaunchManagerVisitor();
-		}
-		return fgVisitor;
-	}
-
-	/**
-	 * Returns the resource delta visitor for auto-removal of mapped launch configurations
-	 * @return the resource delta visitor for auto-removal of mapped launch configurations
-	 *
-	 * @since 3.4
-	 */
-	private MappedResourceVisitor getMappedResourceVisitor() {
-		if(fgMRVisitor == null) {
-			fgMRVisitor = new MappedResourceVisitor();
-		}
-		return fgMRVisitor;
-	}
-
 	@Override
 	public String[] getEnvironment(ILaunchConfiguration configuration) throws CoreException {
 		Map<String, String> configEnv = configuration.getAttribute(ATTR_ENVIRONMENT_VARIABLES, (Map<String, String>) null);
@@ -1314,9 +1266,7 @@ public ILaunchConfiguration[] getLaunchConfigurations(int kinds) {
 			return allConfigs.toArray(new ILaunchConfiguration[allConfigs.size()]);
 		} else {
 			List<ILaunchConfiguration> select = new ArrayList<>(allConfigs.size());
-			Iterator<ILaunchConfiguration> iterator = allConfigs.iterator();
-			while (iterator.hasNext()) {
-				ILaunchConfiguration config = iterator.next();
+			for (ILaunchConfiguration config : allConfigs) {
 				try {
 					if ((config.getKind() & kinds) > 0) {
 						select.add(config);
@@ -2126,15 +2076,11 @@ public void removeLaunchListener(ILaunchListener listener) {
 	public void resourceChanged(IResourceChangeEvent event) {
 		IResourceDelta delta = event.getDelta();
 		if (delta != null) {
-			LaunchManagerVisitor visitor = getDeltaVisitor();
-			MappedResourceVisitor v = null;
-			if (isDeleteConfigurations()) {
-				v = getMappedResourceVisitor();
-			}
 			try {
-				delta.accept(visitor);
-				if (v != null) {
-					delta.accept(v);
+				boolean deleteConfigurations = isDeleteConfigurations();
+				delta.accept(fgVisitor);
+				if (deleteConfigurations) {
+					delta.accept(fgMRVisitor);
 				}
 			} catch (CoreException e) {
 				DebugPlugin.log(e.getStatus());
@@ -2150,14 +2096,13 @@ public void resourceChanged(IResourceChangeEvent event) {
 	 * @param resource the resource to collect launch configurations for
 	 * @return the list of associated launch configurations
 	 */
-	private ArrayList<ILaunchConfiguration> collectAssociatedLaunches(IResource resource) {
-		ArrayList<ILaunchConfiguration> list = new ArrayList<>();
+	private static List<ILaunchConfiguration> collectAssociatedLaunches(IResource resource) {
+		List<ILaunchConfiguration> list = new ArrayList<>();
 		try {
 			ILaunchConfiguration[] configs = DebugPlugin.getDefault().getLaunchManager().getLaunchConfigurations();
-			IResource[] resources = null;
 			for (ILaunchConfiguration config : configs) {
 				if(config.isLocal()) {
-					resources = config.getMappedResources();
+					IResource[] resources = config.getMappedResources();
 					if(resources != null) {
 						for (IResource res : resources) {
 							if(resource.equals(res) ||