Fix some issues raised by Copilot

Author: leerho

src/main/java/org/apache/datasketches/theta/CompactOperations.java

@@ -113,6 +113,7 @@ static CompactThetaSketch componentsToCompact( //No error checking
    * @param srcSeg the given input source MemorySegment image. Can be Read Only.
    * @param dstOrdered the desired ordering of the resulting CompactThetaSketch
    * @param dstWSeg Used for the target CompactThetaSketch if it is MemorySegment-based. Must be Writable.
+   * If null, return on-heap.
    * @return a CompactThetaSketch of the correct form.
    */
   @SuppressWarnings("unused")

src/test/java/org/apache/datasketches/theta/DirectIntersectionTest.java

@@ -369,15 +369,12 @@ public void checkEstimatingIntersect() {
     println("Est: "+est);
   }
 
-  @SuppressWarnings("unused")
   @Test(expectedExceptions = SketchesArgumentException.class)
   public void checkOverflow() {
     final int lgK = 9; //512
     final int k = 1<<lgK;
     ThetaIntersection inter;
     UpdatableThetaSketch sk1;
-    final UpdatableThetaSketch sk2;
-    final CompactThetaSketch comp1;
     final double est;
 
     final int reqBytes = getMaxIntersectionBytes(k);

src/test/java/org/apache/datasketches/theta/HeapAlphaSketchTest.java

@@ -670,7 +670,6 @@ public void checkFamily() {
     assertEquals(sketch.getFamily(), Family.ALPHA);
   }
 
-  @SuppressWarnings("unused")
   @Test(expectedExceptions = SketchesArgumentException.class)
   public void corruptionLgNomLongs() {
     final int k = 512;
@@ -680,7 +679,7 @@ public void corruptionLgNomLongs() {
     byte[] byteArr = sketch.toByteArray();
     MemorySegment wseg = MemorySegment.ofArray(byteArr);
     wseg.set(JAVA_BYTE, LG_NOM_LONGS_BYTE, (byte) 8); //corrupt LgNomLongs
-    UpdatableThetaSketch sk = UpdatableThetaSketch.heapify(wseg);
+    UpdatableThetaSketch.heapify(wseg);
   }
 
   @Test

src/test/java/org/apache/datasketches/theta/UpdateSketchTest.java

@@ -39,10 +39,6 @@
 import org.apache.datasketches.common.ResizeFactor;
 import org.apache.datasketches.common.SketchesArgumentException;
 import org.apache.datasketches.common.Util;
-import org.apache.datasketches.theta.CompactOperations;
-import org.apache.datasketches.theta.CompactThetaSketch;
-import org.apache.datasketches.theta.UpdatableThetaSketch;
-import org.apache.datasketches.theta.UpdateSketchBuilder;
 import org.apache.datasketches.thetacommon.ThetaUtil;
 import org.testng.annotations.Test;
 
@@ -204,8 +200,6 @@ public void checkIsResizeFactorIncorrect() {
     }
   }
 
-
-  @SuppressWarnings("unused")
   @Test
   public void checkCompactOpsMemorySegmentToCompact() {
     MemorySegment skwseg, cskwseg1, cskwseg2, cskwseg3;
@@ -216,15 +210,18 @@ public void checkCompactOpsMemorySegmentToCompact() {
     for (int i = 2; i < n; i++) { sk.update(i); }
     final int cbytes = sk.getCompactBytes();
     final byte[] byteArr = sk.toByteArray();
-    skwseg = MemorySegment.ofArray(byteArr);
-    cskwseg1 = MemorySegment.ofArray(new byte[cbytes]);
-    cskwseg2 = MemorySegment.ofArray(new byte[cbytes]);
-    cskwseg3 = MemorySegment.ofArray(new byte[cbytes]);
-    csk1 = sk.compact(true, cskwseg1);
-    csk2 = CompactOperations.segmentToCompact(skwseg, true, cskwseg2);
+    skwseg = MemorySegment.ofArray(byteArr); //updatable seg
+    cskwseg1 = MemorySegment.ofArray(new byte[cbytes]); //empty
+    cskwseg2 = MemorySegment.ofArray(new byte[cbytes]); //empty
+    cskwseg3 = MemorySegment.ofArray(new byte[cbytes]); //empty
+    csk1 = sk.compact(true, cskwseg1); //cskwseg1 has compact sk image, csk1 is the sketch
+    csk2 = CompactOperations.segmentToCompact(skwseg, true, cskwseg2); //cskwseg2 has compact skwseg image
     csk3 = CompactOperations.segmentToCompact(cskwseg1, true, cskwseg3);
     assertTrue(equalContents(cskwseg1,cskwseg2));
     assertTrue(equalContents(cskwseg1, cskwseg3));
+    assertTrue(csk1.hasMemorySegment());
+    assertTrue(csk2.hasMemorySegment());
+    assertTrue(csk3.hasMemorySegment());
   }
 
   @Test