Take advantage of Java 25 Flexible Constructor Bodies JEP 513.

And remove the awkward constructors used to avoid Finalizer Attacks.

Author: leerho

src/main/java/org/apache/datasketches/quantiles/DoublesSketchAccessor.java

@@ -44,26 +44,16 @@ abstract class DoublesSketchAccessor extends DoublesBufferAccessor {
     final DoublesSketch ds,
     final boolean forceSize,
     final int level) {
-    this(checkLvl(level), ds, forceSize, level);
-    //SpotBugs CT_CONSTRUCTOR_THROW is false positive.
-    //this construction scheme is compliant with SEI CERT Oracle Coding Standard for Java / OBJ11-J
-  }
-
-  private DoublesSketchAccessor(
-      @SuppressWarnings("unused") final boolean secure, //required part of Finalizer Attack prevention
-      final DoublesSketch ds,
-      final boolean forceSize,
-      final int level) {
+	checkLvl(level);
     ds_ = ds;
     forceSize_ = forceSize;
     setLevel(level);
   }
 
-  private static final boolean checkLvl(final int level) {
+  private static final void checkLvl(final int level) {
     if ((level != BB_LVL_IDX) && (level < 0)) {
       throw new SketchesArgumentException("Parameter level is < 0.");
     }
-    return true;
   }
 
   /**

src/main/java/org/apache/datasketches/tuple/QuickSelectSketch.java

@@ -135,8 +135,9 @@ private QuickSelectSketch(
       final float samplingProbability,
       final SummaryFactory<S> summaryFactory,
       final int startingSize) {
+      final long thetaLong = (long) (Long.MAX_VALUE * (double) samplingProbability);
     super(
-        (long) (Long.MAX_VALUE * (double) samplingProbability),
+        thetaLong,
         true,
         summaryFactory);
     nomEntries_ = ceilingPowerOf2(nomEntries);
@@ -182,23 +183,9 @@ private QuickSelectSketch(
       final MemorySegment seg,
       final SummaryDeserializer<S> deserializer,
       final SummaryFactory<S> summaryFactory) {
-    this(new Validate<>(), seg, deserializer, summaryFactory);
-  }
-
-  /*
-   * This private constructor is used to protect against "Finalizer attacks".
-   * The private static inner class Validate performs validation and deserialization
-   * from the input MemorySegment and may throw exceptions. In order to protect against the attack, we must
-   * perform this validation prior to the constructor's super reaches the Object class.
-   * Making QuickSelectSketch final won't work here because UpdatableSketch is a subclass.
-   * Using an empty final finalizer() is not recommended and is deprecated as of Java9.
-   */
-  private QuickSelectSketch(
-      final Validate<S> val,
-      final MemorySegment seg,
-      final SummaryDeserializer<S> deserializer,
-      final SummaryFactory<S> summaryFactory) {
-    super(val.validate(seg, deserializer), val.myEmpty, summaryFactory);
+    //this(new Validate<>(), seg, deserializer, summaryFactory);
+    final Validate<S> val = new Validate<>();
+    final long thetaLong = val.validate(seg, deserializer);
     nomEntries_ = val.myNomEntries;
     lgResizeFactor_ = val.myLgResizeFactor;
     samplingProbability_ = val.mySamplingProbability;
@@ -207,6 +194,7 @@ private QuickSelectSketch(
     rebuildThreshold_ = val.myRebuildThreshold;
     hashTable_ = val.myHashTable;
     summaryTable_ = val.mySummaryTable;
+    super(thetaLong, val.myEmpty, summaryFactory);
   }
 
   private static final class Validate<S> {

src/main/java/org/apache/datasketches/tuple/arrayofdoubles/DirectArrayOfDoublesQuickSelectSketch.java

@@ -79,25 +79,7 @@ class DirectArrayOfDoublesQuickSelectSketch extends ArrayOfDoublesQuickSelectSke
       final int numValues,
       final long seed,
       final MemorySegment dstSeg) {
-    this(checkMemorySegment(nomEntries, lgResizeFactor, numValues, dstSeg),
-    //SpotBugs CT_CONSTRUCTOR_THROW is false positive.
-    //this construction scheme is compliant with SEI CERT Oracle Coding Standard for Java / OBJ11-J
-        nomEntries,
-        lgResizeFactor,
-        samplingProbability,
-        numValues,
-        seed,
-        dstSeg);
-  }
-
-  private DirectArrayOfDoublesQuickSelectSketch(
-      @SuppressWarnings("unused") final boolean secure, //required part of Finalizer Attack prevention
-      final int nomEntries,
-      final int lgResizeFactor,
-      final float samplingProbability,
-      final int numValues,
-      final long seed,
-      final MemorySegment dstSeg) {
+    checkMemorySegment(nomEntries, lgResizeFactor, numValues, dstSeg);
     super(numValues, seed);
     seg_ = dstSeg;
     final int startingCapacity = Util.getStartingCapacity(nomEntries, lgResizeFactor);
@@ -126,14 +108,13 @@ private DirectArrayOfDoublesQuickSelectSketch(
     setRebuildThreshold();
   }
 
-  private static final boolean checkMemorySegment(
+  private static final void checkMemorySegment(
       final int nomEntries,
       final int lgResizeFactor,
       final int numValues,
       final MemorySegment dstSeg) {
     final int startingCapacity = Util.getStartingCapacity(nomEntries, lgResizeFactor);
     checkMemorySegmentSize(dstSeg, startingCapacity, numValues);
-    return true;
   }
 
   /**
@@ -144,15 +125,7 @@ private static final boolean checkMemorySegment(
   DirectArrayOfDoublesQuickSelectSketch(
       final MemorySegment seg,
       final long seed) {
-    this(checkSerVer(seg), seg, seed);
-    //SpotBugs CT_CONSTRUCTOR_THROW is false positive.
-    //this construction scheme is compliant with SEI CERT Oracle Coding Standard for Java / OBJ11-J
-  }
-
-  private DirectArrayOfDoublesQuickSelectSketch(
-      @SuppressWarnings("unused") final boolean secure, //required part of Finalizer Attack prevention
-      final MemorySegment seg,
-      final long seed) {
+    checkSerVer(seg);
     super(seg.get(JAVA_BYTE, NUM_VALUES_BYTE), seed);
     seg_ = seg;
     SerializerDeserializer.validateFamily(seg.get(JAVA_BYTE, FAMILY_ID_BYTE),
@@ -170,13 +143,12 @@ private DirectArrayOfDoublesQuickSelectSketch(
     setRebuildThreshold();
   }
 
-  private static final boolean checkSerVer(final MemorySegment seg) {
+  private static final void checkSerVer(final MemorySegment seg) {
     final byte version = seg.get(JAVA_BYTE, SERIAL_VERSION_BYTE);
     if (version != serialVersionUID) {
       throw new SketchesArgumentException("Serial version mismatch. Expected: " + serialVersionUID
           + ", actual: " + version);
     }
-    return true;
   }
 
   @Override