(v2.5.1) Don't err when sampling/shuffling empty collections

Actually sampling will not throw only when number of elements to return
is 0. In all other cases it will still throw.

datagen/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>qala-datagen-parent</artifactId>
         <groupId>io.qala.datagen</groupId>
-        <version>2.5.0</version>
+        <version>2.5.1</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

datagen/src/main/java/io/qala/datagen/RandomElements.java

@@ -13,8 +13,6 @@ private RandomElements(T[] elements) {
     }
 
     private RandomElements(Collection<T> elements) {
-        if(elements == null || elements.isEmpty())
-            throw new IllegalArgumentException("Can't sample from zero elements: " + elements);
         this.elements = new ArrayList<T>(elements);
     }
 
@@ -42,6 +40,7 @@ private RandomElements(Collection<T> elements) {
      * @return a random element from the collection
      */
     public T sample() {
+        assertCollectionIsNotEmpty();
         int index = integer(size() - 1);
         return this.elements.get(index);
     }
@@ -79,6 +78,8 @@ public List<T> sample(int nToReturn) {
      * @return collection of random elements picked from the initial collection
      */
     public List<T> sampleWithReplacement(int nToReturn) {
+        if(nToReturn > 0)
+            assertCollectionIsNotEmpty();
         List<T> result = new ArrayList<T>(nToReturn);
         for(int i = 0; i < nToReturn; i++) {
             int index = integer(size() - 1);
@@ -101,4 +102,9 @@ public List<T> shuffled() {
     private int size() {
         return elements.size();
     }
+
+    private void assertCollectionIsNotEmpty() {
+        if(elements.isEmpty())
+            throw new IllegalArgumentException("Can't sample from zero elements: " + elements);
+    }
 }

datagen/src/test/java/io/qala/datagen/RandomElementsTest.java

@@ -9,7 +9,8 @@
 
 import static io.qala.datagen.RandomElements.from;
 import static io.qala.datagen.RandomShortApi.*;
-import static io.qala.datagen.RandomValue.*;
+import static io.qala.datagen.RandomValue.between;
+import static io.qala.datagen.RandomValue.length;
 import static java.util.Collections.emptyList;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
@@ -49,14 +50,18 @@ class RandomElementsTest {
         assertThat(from("element1", "element2").sample(2), containsInAnyOrder("element1", "element2"));
         assertThat(sampleMultiple(2, "element1", "element2"), containsInAnyOrder("element1", "element2"));
     }
+    @Test void sampleMultiple_returnsEmptyList_ifSampling0elements() {
+        assertEquals(0, sampleMultiple(0).size());
+        assertEquals(0, from().sampleWithReplacement(0).size());
+    }
 
     @Test void mustThrowIfSampleIsLargerThanPopulation() {
         assertThrows(IllegalArgumentException.class, () -> from("el", "el2").sample(3));
         assertThrows(IllegalArgumentException.class, () -> sampleMultiple(3, "el", "el2"));
     }
     @Test void throwsIfCollectionToSampleFromIsEmpty() {
         assertThrows(IllegalArgumentException.class, () -> from().sample(3));
-        assertThrows(IllegalArgumentException.class, () -> sampleMultiple(0));
+        assertThrows(IllegalArgumentException.class, () -> from().sampleWithReplacement(1));
         assertThrows(IllegalArgumentException.class, RandomShortApi::sample);
     }
     @Test void canSampleMultipleElementsFromList() {
@@ -67,7 +72,6 @@ class RandomElementsTest {
         assertThat(population, hasItems(sample.toArray(new String[0])));
     }
     @Test void samplesDuplicateElements_ifSampleSizeLargerThanPopulation_andSamplingIsWithReplacement() {
-        System.out.println(from("A", "B", "C").shuffled());
         List<String> population = between(0, 10).alphanumerics(2);
         List<String> sample = from(population).sampleWithReplacement(5);
 
@@ -100,6 +104,10 @@ class RandomElementsTest {
         assertTrue(original.containsAll(shuffled));
         assertTrue(shuffled.containsAll(original));
     }
+    @Test void shufflingEmptyCollection_returnsEmptyCollection() {
+        assertEquals(0, shuffled(emptyList()).size());
+        assertEquals(0, shuffled().size());
+    }
 
     @Test void nullOrObj_returnsNull_sometimes() {
         for(int i = 0; i < 100; i++) if (nullOr("str") == null) return;

examples/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>qala-datagen-parent</artifactId>
         <groupId>io.qala.datagen</groupId>
-        <version>2.5.0</version>
+        <version>2.5.1</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

java8types/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>qala-datagen-parent</artifactId>
         <groupId>io.qala.datagen</groupId>
-        <version>2.5.0</version>
+        <version>2.5.1</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

junit5/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>qala-datagen-parent</artifactId>
         <groupId>io.qala.datagen</groupId>
-        <version>2.5.0</version>
+        <version>2.5.1</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

pom.xml

@@ -7,7 +7,7 @@
     <groupId>io.qala.datagen</groupId>
     <artifactId>qala-datagen-parent</artifactId>
     <packaging>pom</packaging>
-    <version>2.5.0</version>
+    <version>2.5.1</version>
 
     <licenses>
         <license>