From 1c150e207ab0d2e9fa96b976a1a5ee49836f5f86 Mon Sep 17 00:00:00 2001
From: Darin Kelkhoff <darin.kelkhoff@gmail.com>
Date: Thu, 19 Jan 2023 16:11:54 -0600
Subject: [PATCH] add nonNullArray and mergeLists

---
 .../backend/core/utils/CollectionUtils.java   | 37 +++++++++++++++
 .../core/utils/CollectionUtilsTest.java       | 45 +++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java b/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java
index c75fa727..08526658 100755
--- a/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java
+++ b/qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/CollectionUtils.java
@@ -415,6 +415,22 @@ public class CollectionUtils
 
 
 
+   /*******************************************************************************
+    ** Returns the input array, unless it was null - in which case a new (empty) array is returned.
+    **
+    ** Meant to help avoid null checks on foreach loops.
+    *******************************************************************************/
+   public static <T> T[] nonNullArray(T[] array)
+   {
+      if(array == null)
+      {
+         return (T[]) new ArrayList<T>().toArray();
+      }
+      return (array);
+   }
+
+
+
    /*******************************************************************************
     ** Returns the input list, unless it was null - in which case a new array list is returned.
     **
@@ -513,4 +529,25 @@ public class CollectionUtils
       return (mapper.convertValue(o, Map.class));
    }
 
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   public static <T> List<T> mergeLists(List<T>... lists)
+   {
+      List<T> rs = new ArrayList<>();
+      if(lists != null)
+      {
+         for(List<T> list : lists)
+         {
+            if(list != null)
+            {
+               rs.addAll(list);
+            }
+         }
+      }
+      return (rs);
+   }
+
 }
diff --git a/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java b/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java
index 06dd2475..860a4ba6 100644
--- a/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java
+++ b/qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/CollectionUtilsTest.java
@@ -30,6 +30,7 @@ import java.util.Map;
 import java.util.function.Function;
 import com.kingsrook.qqq.backend.core.BaseTest;
 import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
@@ -499,4 +500,48 @@ class CollectionUtilsTest extends BaseTest
       assertEquals(list, accumulator);
    }
 
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Test
+   void testNonNullArray()
+   {
+      assertArrayEquals(new Integer[] { }, CollectionUtils.nonNullArray(null));
+      assertArrayEquals(new Integer[] { }, CollectionUtils.nonNullArray(new Integer[] { }));
+      assertArrayEquals(new Integer[] { 1, 2, 3 }, CollectionUtils.nonNullArray(new Integer[] { 1, 2, 3 }));
+   }
+
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Test
+   void testNonNullList()
+   {
+      assertEquals(List.of(), CollectionUtils.nonNullList(null));
+      assertEquals(List.of(), CollectionUtils.nonNullList(List.of()));
+      assertEquals(List.of(1, 2, 3), CollectionUtils.nonNullList(List.of(1, 2, 3)));
+   }
+
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Test
+   void testMergeLists()
+   {
+      assertEquals(List.of(), CollectionUtils.mergeLists());
+      assertEquals(List.of(), CollectionUtils.mergeLists((List<Object>) null));
+      assertEquals(List.of(), CollectionUtils.mergeLists((List<Object>[]) null));
+      assertEquals(List.of(), CollectionUtils.mergeLists(List.of()));
+      assertEquals(List.of(1, 2, 3), CollectionUtils.mergeLists(List.of(1, 2, 3)));
+      assertEquals(List.of(1, 2, 3), CollectionUtils.mergeLists(List.of(1, 2), List.of(3)));
+      assertEquals(List.of(1, 2, 3), CollectionUtils.mergeLists(List.of(1, 2), null, List.of(3)));
+      assertEquals(List.of(1, 2, 3), CollectionUtils.mergeLists(null, List.of(1, 2, 3), null));
+   }
+
 }