Merge pull request #63 from eclipse-mat/slow-object-marker-cleanup

perf: use Set instead of List to track subClasses in GarbageCleaner

plugins/org.eclipse.mat.parser/src/org/eclipse/mat/parser/model/ClassImpl.java

@@ -19,8 +19,10 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 import java.util.concurrent.atomic.AtomicLongFieldUpdater;
 
@@ -67,7 +69,7 @@ public class ClassImpl extends AbstractObjectImpl implements IClass, Comparable<
  protected volatile long totalSize;
  protected boolean isArrayType;
 
- private List<IClass> subClasses;
+ private Set<IClass> subClasses;
 
  private Serializable cacheEntry;
 
@@ -392,14 +394,14 @@ void removeInstanceBulk(int instanceCount, long heapSize)
  @SuppressWarnings("unchecked")
  public List<IClass> getSubclasses()
  {
- return subClasses != null ? subClasses : Collections.EMPTY_LIST;
+ return (subClasses == null) ? Collections.emptyList() : new ArrayList<>(subClasses);
  }
 
  @Override
  public List<IClass> getAllSubclasses()
  {
  if (subClasses == null || subClasses.isEmpty())
- return new ArrayList<IClass>();
+ return Collections.emptyList();
 
  List<IClass> answer = new ArrayList<IClass>(subClasses.size() * 2);
  answer.addAll(this.subClasses);
@@ -453,7 +455,7 @@ public int getClassLoaderId()
  public void addSubClass(ClassImpl clazz)
  {
  if (subClasses == null)
- subClasses = new ArrayList<IClass>();
+ subClasses = new LinkedHashSet<IClass>();
  subClasses.add(clazz);
  }