extended CollectionHelper by isEmpty test

src/main/java/org/logicng/util/CollectionHelper.java

@@ -19,6 +19,16 @@ private CollectionHelper() {
         // Intentionally left empty
     }
 
+    /**
+     * Null safe test whether the given collection is empty, i.e. tests if the collection is {@code null} or empty.
+     * @param collection the collection, may be {@code null}
+     * @param <T>        the type of the elements in the collection, may be arbitrary
+     * @return {@code true} if the collection is {@code null} or empty, otherwise {@code false}
+     */
+    public static <T> boolean isEmpty(final Collection<T> collection) {
+        return collection == null || collection.isEmpty();
+    }
+
     /**
      * Null safe wrapper for collections. Returns an (unmodifiable!) empty list if the given collection is {@code
      * null}, otherwise returns the given list unchanged.

src/test/java/org/logicng/util/CollectionHelperTest.java

@@ -1,8 +1,5 @@
 package org.logicng.util;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.logicng.util.CollectionHelper.nullSafe;
-
 import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
@@ -12,13 +9,25 @@
 import java.util.SortedSet;
 import java.util.TreeSet;
 
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.logicng.util.CollectionHelper.isEmpty;
+import static org.logicng.util.CollectionHelper.nullSafe;
+
 /**
  * Unit tests for {@link CollectionHelper}
  * @version 2.0.0
  * @since 2.0.0
  */
 public class CollectionHelperTest {
 
+    @Test
+    public void testIsEmpty() {
+        assertThat(isEmpty(null)).isTrue();
+        assertThat(isEmpty(Collections.emptySet())).isTrue();
+        assertThat(isEmpty(Collections.emptyMap().entrySet())).isTrue();
+        assertThat(isEmpty(Collections.singletonList(2))).isFalse();
+    }
+
     @Test
     public void testNullSafe() {
         assertThat(nullSafe(null)).isEmpty();