Minor fixes for a SpotBugs issue

Author: leerho

src/main/java/org/apache/datasketches/common/MemorySegmentStatus.java

@@ -44,8 +44,6 @@ public interface MemorySegmentStatus {
    * Returns true if an internally referenced MemorySegment has the same backing resource as <i>that</i>,
    * or equivalently, if their two memory regions overlap.  This applies to both on-heap and off-heap MemorySegments.
    *
-   * <p>This returns false if either segment is <i>null</i> or not alive.</p>
-   *
    * <p><b>Note:</b> If both segments are on-heap and not read-only, it can be determined if they were derived from
    * the same backing memory (array).  However, this is not always possible off-heap. Because of this asymmetry, this definition
    * of "isSameResource" is confined to the existence of an overlap.</p>
@@ -59,8 +57,6 @@ public interface MemorySegmentStatus {
    * Returns true if the two given MemorySegments have to the same backing resource, or equivalently,
    * if the two memory regions overlap.  This applies to both on-heap and off-heap MemorySegments.
    *
-   * <p>This returns false if either segment is <i>null</i> or not alive.</p>
-   *
    * <p><b>Note:</b> If both segments are on-heap and not read-only, it can be determined if they were derived from
    * the same backing memory (array).  However, this is not always possible off-heap. Because of this asymmetry, this definition
    * of "isSameResource" is confined to the existence of an overlap.</p>
@@ -70,7 +66,6 @@ public interface MemorySegmentStatus {
    * @return true if the two given MemorySegments have to the same backing resource.
    */
   static boolean isSameResource(final MemorySegment seg1, final MemorySegment seg2) {
-    if ((seg1 == null) || (seg2 == null) || !seg1.scope().isAlive() || !seg2.scope().isAlive()) { return false; }
     final Optional<MemorySegment> opt = seg1.asOverlappingSlice(seg2);
     return opt.isPresent();
   }

src/test/java/org/apache/datasketches/hll/SizeAndModeTransitions.java

@@ -33,22 +33,27 @@ public class SizeAndModeTransitions {
   static String[] hdr = {"Type", "Store", "LgK", "N", "Mode", "ActCBytes", "CmpBytes", "ActUBytes", "UpdBytes", "MaxBytes", "Estimate"};
 
   @Test
-  public void checkHLL8Heap() {
+  public void checkHLL8with_withoutSeg() {
+    checkHLL8Heap(true);
+    checkHLL8Heap(false);
+  }
+
+  private void checkHLL8Heap(final boolean withSeg) {
     final TgtHllType tgtHllType = TgtHllType.HLL_8;
-    final boolean offHeap = false;
     final int lgK = 10;
     final int N = 97;
     printf(hfmt, (Object[]) hdr);
-    final int maxBytes = HllSketch.getMaxUpdatableSerializationBytes(lgK, tgtHllType);
+
     MemorySegment wseg = null;
     HllSketch sk;
-    if (offHeap) {
+    if (withSeg) {
+      final int maxBytes = HllSketch.getMaxUpdatableSerializationBytes(lgK, tgtHllType);
       wseg = MemorySegment.ofArray(new byte[maxBytes]);
       sk = new HllSketch(lgK, tgtHllType, wseg);
     } else {
-      sk = new HllSketch(lgK, tgtHllType);
+      sk = new HllSketch(lgK, tgtHllType); //without segment
     }
-    final String store = offHeap ? "MemorySegment" : "Heap";
+    final String store = withSeg ? "MemorySegment" : "Heap";
     for (int i = 1; i <= N; i++) {
       sk.update(i);
       if (i == 7)  { checkAtN(sk, tgtHllType, store, lgK, i, "LIST",  36,   40, 1064); }

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

@@ -343,9 +343,6 @@ public void checkIsSameResource() {
     final DirectCompactSketch dcs = (DirectCompactSketch) sketch.compact(false, cseg);
     assertTrue(MemorySegmentStatus.isSameResource(dcs.getMemorySegment(), cseg));
     assertFalse(dcs.isOrdered());
-
-    final Sketch sk = Sketches.updateSketchBuilder().setNominalEntries(k).build();
-    assertFalse(MemorySegmentStatus.isSameResource(sk.getMemorySegment(),seg));
   }
 
   @Test