EclipsePreferences: use simple HashMap

Using a concurrent Map is a waste as every access is guarded by
childAndPropertyLock anyway.

+ add missing guards (was used unguarded in RootPreferences)
+ make getChild(String key, Object context, boolean create) atomic

bundles/org.eclipse.equinox.preferences/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.equinox.preferences; singleton:=true
-Bundle-Version: 3.11.100.qualifier
+Bundle-Version: 3.11.200.qualifier
 Bundle-Activator: org.eclipse.core.internal.preferences.Activator
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin

bundles/org.eclipse.equinox.preferences/src/org/eclipse/core/internal/preferences/EclipsePreferences.java

@@ -22,7 +22,6 @@
 import java.nio.file.*;
 import java.nio.file.Path;
 import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
 import org.eclipse.core.internal.runtime.RuntimeLog;
 import org.eclipse.core.runtime.*;
 import org.eclipse.core.runtime.preferences.*;
@@ -58,8 +57,10 @@ public class EclipsePreferences implements IEclipsePreferences, IScope {
  private static final String BACKUP_FILE_EXTENSION = ".bak"; //$NON-NLS-1$
 
  private String cachedPath;
- protected ImmutableMap properties = ImmutableMap.EMPTY;
- protected Map<String, Object> children;
+ /** synchronized by childAndPropertyLock */
+ private ImmutableMap properties = ImmutableMap.EMPTY;
+ /** synchronized by childAndPropertyLock */
+ private Map<String, Object> children;
  /**
  * Protects write access to properties and children.
  */
@@ -125,12 +126,11 @@ public void accept(IPreferenceNodeVisitor visitor) throws BackingStoreException
  }
 
  protected IEclipsePreferences addChild(String childName, IEclipsePreferences child) {
- // Thread safety: synchronize method to protect modification of children field
  synchronized (childAndPropertyLock) {
  if (children == null) {
- children = new ConcurrentHashMap<>();
+ children = new HashMap<>();
  }
- children.put(childName, child == null ? (Object) childName : child);
+ children.put(childName, child == null ? childName : child);
  return child;
  }
  }
@@ -469,7 +469,7 @@ protected boolean childExists(String childName) {
  if (children == null) {
  return false;
  }
- return children.get(childName) != null;
+ return children.containsKey(childName);
  }
  }
 
@@ -493,8 +493,8 @@ protected IEclipsePreferences getChild(String key, Object context, boolean creat
  if (!create) {
  return null;
  }
+ return addChild(key, create(this, key, context));
  }
- return addChild(key, create(this, key, context));
  }
 
  /**
@@ -1144,4 +1144,29 @@ public String toString() {
  void setDescriptor(ScopeDescriptor descriptor) {
  this.descriptor = descriptor;
  }
+
+ protected IEclipsePreferences getOrCreate(String scope) {
+ IEclipsePreferences child;
+ synchronized (childAndPropertyLock) {
+ if (children == null) {
+ child = null;
+ } else {
+ Object value = children.get(scope);
+ if (value == null) {
+ child = null;
+ } else if (value instanceof IEclipsePreferences eclipsePreferences) {
+ child = eclipsePreferences;
+ } else {
+ // lazy initialization
+ child = PreferencesService.getDefault().createNode(scope);
+ addChild(scope, child);
+ }
+ }
+ if (child == null) {
+ child = new EclipsePreferences(this, scope);
+ addChild(scope, child);
+ }
+ }
+ return child;
+ }
 }

bundles/org.eclipse.equinox.preferences/src/org/eclipse/core/internal/preferences/PreferencesService.java

@@ -128,7 +128,7 @@ public IStatus applyPreferences(IExportedPreferences preferences) throws CoreExc
 
  // iterate over the preferences in this node and set them
  // in the global space.
- String[] keys = epNode.properties.keys();
+ String[] keys = epNode.keys();
 
  // if this node was removed then we need to create a new one
  if (removed) {

bundles/org.eclipse.equinox.preferences/src/org/eclipse/core/internal/preferences/RootPreferences.java

@@ -48,23 +48,6 @@ public void flush() throws BackingStoreException {
  }
  }
 
- private synchronized IEclipsePreferences getChild(String key) {
- if (children == null) {
- return null;
- }
- Object value = children.get(key);
- if (value == null) {
- return null;
- }
- if (value instanceof IEclipsePreferences eclipsePreferences) {
- return eclipsePreferences;
- }
- // lazy initialization
- IEclipsePreferences child = PreferencesService.getDefault().createNode(key);
- addChild(key, child);
- return child;
- }
-
  @Override
  public Preferences node(String path) {
  return getNode(path, true); // create if not found
@@ -79,11 +62,7 @@ public Preferences getNode(String path, boolean create) {
  String scope = path.substring(startIndex, endIndex == -1 ? path.length() : endIndex);
  IEclipsePreferences child;
  if (create) {
- child = getChild(scope);
- if (child == null) {
- child = new EclipsePreferences(this, scope);
- addChild(scope, child);
- }
+ child = getOrCreate(scope);
  } else {
  child = getChild(scope, null, false);
  if (child == null) {