Found a minor Javadoc vs implementation discrepancy.

src/main/java/org/apache/datasketches/quantilescommon/QuantilesDoublesAPI.java

@@ -253,7 +253,7 @@ default double[] getQuantiles(int numEvenlySpaced) {
    * @param searchCrit if INCLUSIVE, the given ranks include all quantiles ≤ the quantile directly corresponding to
    * each rank.
    * @return an array of quantiles that are evenly spaced by their ranks.
-   * @throws IllegalArgumentException if sketch is empty.
+   * @throws IllegalArgumentException if sketch is empty or if <i>numEvenlySpaced is less than 1</i>.
    * @see org.apache.datasketches.quantilescommon.QuantileSearchCriteria
    */
   double[] getQuantiles(int numEvenlySpaced, QuantileSearchCriteria searchCrit);

src/main/java/org/apache/datasketches/quantilescommon/QuantilesFloatsAPI.java

@@ -252,7 +252,7 @@ default float[] getQuantiles(int numEvenlySpaced) {
    * @param searchCrit if INCLUSIVE, the given ranks include all quantiles ≤ the quantile directly corresponding to
    * each rank.
    * @return an array of quantiles that are evenly spaced by their ranks.
-   * @throws IllegalArgumentException if sketch is empty.
+   * @throws IllegalArgumentException if sketch is empty or if <i>numEvenlySpaced is less than 1</i>.
    * @see org.apache.datasketches.quantilescommon.QuantileSearchCriteria
    */
   float[] getQuantiles(int numEvenlySpaced, QuantileSearchCriteria searchCrit);

src/main/java/org/apache/datasketches/quantilescommon/QuantilesGenericAPI.java

@@ -253,7 +253,7 @@ default T[] getQuantiles(int numEvenlySpaced) {
    * @param searchCrit if INCLUSIVE, the given ranks include all quantiles ≤ the quantile directly corresponding to
    * each rank.
    * @return an array of quantiles that are evenly spaced by their ranks.
-   * @throws IllegalArgumentException if sketch is empty.
+   * @throws IllegalArgumentException if sketch is empty or if <i>numEvenlySpaced is less than 1</i>.
    * @see org.apache.datasketches.quantilescommon.QuantileSearchCriteria
    */
   T[] getQuantiles(int numEvenlySpaced, QuantileSearchCriteria searchCrit);

src/main/java/org/apache/datasketches/quantilescommon/QuantilesUtil.java

@@ -83,22 +83,24 @@ public static final void checkFloatsSplitPointsOrder(final float[] values) {
    * Returns a double array of evenly spaced values between value1 and value2 inclusive.
    * If value2 > value1, the resulting sequence will be increasing.
    * If value2 < value1, the resulting sequence will be decreasing.
+   * If num == 1, value1 will be in index 0 of the returned array.
    * @param value1 will be in index 0 of the returned array
    * @param value2 will be in the highest index of the returned array
-   * @param num the total number of values including value1 and value2. Must be 2 or greater.
+   * @param num the total number of values including value1 and value2. Must be 1 or greater.
    * @return a double array of evenly spaced values between value1 and value2 inclusive.
+   * @throws IllegalArgumentException if <i>num</i> is less than 1.
    */
   public static double[] evenlySpaced(final double value1, final double value2, final int num) {
-    if (num < 2) {
-      throw new SketchesArgumentException("num must be >= 2");
+    if (num < 1) {
+      throw new IllegalArgumentException("num must be >= 1");
     }
     final double[] out = new double[num];
     out[0] = value1;
+    if (num == 1) { return out; }
     out[num - 1] = value2;
     if (num == 2) { return out; }
 
     final double delta = (value2 - value1) / (num - 1);
-
     for (int i = 1; i < num - 1; i++) { out[i] = i * delta + value1; }
     return out;
   }

src/test/java/org/apache/datasketches/quantiles/HeapUpdateDoublesSketchTest.java

@@ -791,7 +791,7 @@ public void checkEvenlySpacedQuantiles() {
     assertEquals(values.length, 11);
   }
 
-  @Test(expectedExceptions = SketchesArgumentException.class)
+  @Test(expectedExceptions = IllegalArgumentException.class)
   public void checkEvenlySpacedQuantilesException() {
     DoublesSketch qsk = buildAndLoadQS(32, 1001);
     qsk.getQuantiles(1);

src/test/java/org/apache/datasketches/quantiles/ItemsSketchTest.java

@@ -378,7 +378,7 @@ public void checkDownsampleException() {
     sketch.downSample(32);
   }
 
-  @Test(expectedExceptions = SketchesArgumentException.class)
+  @Test(expectedExceptions = IllegalArgumentException.class)
   public void zeroEvenlySpacedMustThrow() {
     final ItemsSketch<String> sketch = ItemsSketch.getInstance(String.class, 16, Comparator.naturalOrder());
     sketch.update("a");