make a new collection if given a null one as input.

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/collections/MutableList.java

@@ -27,6 +27,7 @@ import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
 import java.util.ListIterator;
+import java.util.Objects;
 import java.util.function.Supplier;
 import com.kingsrook.qqq.backend.core.utils.lambdas.VoidVoidMethod;
 
@@ -39,7 +40,7 @@ import com.kingsrook.qqq.backend.core.utils.lambdas.VoidVoidMethod;
 public class MutableList<T> implements List<T>
 {
    private List<T>           sourceList;
-   private Class<? extends List<T>> mutableTypeIfNeeded;
+   private Supplier<List<T>> supplierIfNeeded;
 
 
 
@@ -49,7 +50,7 @@ public class MutableList<T> implements List<T>
     *******************************************************************************/
    public MutableList(List<T> sourceList)
    {
-      this(sourceList, (Class) ArrayList.class);
+      this(sourceList, ArrayList::new);
    }
 
 
@@ -58,10 +59,20 @@ public class MutableList<T> implements List<T>
     ** Constructor
     **
     *******************************************************************************/
-   public MutableList(List<T> sourceList, Class<? extends List<T>> mutableTypeIfNeeded)
+   public MutableList(List<T> sourceList, Supplier<List<T>> supplierIfNeeded)
    {
-      this.sourceList = sourceList;
-      this.mutableTypeIfNeeded = mutableTypeIfNeeded;
+      this.sourceList = Objects.requireNonNullElseGet(sourceList, supplierIfNeeded);
+      this.supplierIfNeeded = supplierIfNeeded;
+   }
+
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   List<T> getUnderlyingList()
+   {
+      return (sourceList);
    }
 
 
@@ -73,13 +84,13 @@ public class MutableList<T> implements List<T>
    {
       try
       {
-         List<T> replacementList = mutableTypeIfNeeded.getConstructor().newInstance();
+         List<T> replacementList = supplierIfNeeded.get();
          replacementList.addAll(sourceList);
          sourceList = replacementList;
       }
       catch(Exception e)
       {
-         throw (new IllegalStateException("The mutable type provided for this MutableList [" + mutableTypeIfNeeded.getName() + "] could not be instantiated."));
+         throw (new IllegalStateException("Error getting from the supplier provided for this MutableList.", e));
       }
    }
 
@@ -88,7 +99,7 @@ public class MutableList<T> implements List<T>
    /*******************************************************************************
     **
     *******************************************************************************/
-   private <T> T doMutableOperationForValue(Supplier<T> supplier)
+   private <V> V doMutableOperationForValue(Supplier<V> supplier)
    {
       try
       {

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/collections/MutableMap.java

@@ -25,6 +25,7 @@ package com.kingsrook.qqq.backend.core.utils.collections;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.Supplier;
 import com.kingsrook.qqq.backend.core.utils.lambdas.VoidVoidMethod;
@@ -38,7 +39,7 @@ import com.kingsrook.qqq.backend.core.utils.lambdas.VoidVoidMethod;
 public class MutableMap<K, V> implements Map<K, V>
 {
    private Map<K, V>           sourceMap;
-   private Class<? extends Map<K, V>> mutableTypeIfNeeded;
+   private Supplier<Map<K, V>> supplierIfNeeded;
 
 
 
@@ -48,7 +49,7 @@ public class MutableMap<K, V> implements Map<K, V>
     *******************************************************************************/
    public MutableMap(Map<K, V> sourceMap)
    {
-      this(sourceMap, (Class) HashMap.class);
+      this(sourceMap, HashMap::new);
    }
 
 
@@ -57,10 +58,20 @@ public class MutableMap<K, V> implements Map<K, V>
     ** Constructor
     **
     *******************************************************************************/
-   public MutableMap(Map<K, V> sourceMap, Class<? extends Map<K, V>> mutableTypeIfNeeded)
+   public MutableMap(Map<K, V> sourceMap, Supplier<Map<K, V>> supplierIfNeeded)
    {
-      this.sourceMap = sourceMap;
-      this.mutableTypeIfNeeded = mutableTypeIfNeeded;
+      this.sourceMap = Objects.requireNonNullElseGet(sourceMap, supplierIfNeeded);
+      this.supplierIfNeeded = supplierIfNeeded;
+   }
+
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   Map<K, V> getUnderlyingMap()
+   {
+      return (sourceMap);
    }
 
 
@@ -72,13 +83,13 @@ public class MutableMap<K, V> implements Map<K, V>
    {
       try
       {
-         Map<K, V> replacementMap = mutableTypeIfNeeded.getConstructor().newInstance();
+         Map<K, V> replacementMap = supplierIfNeeded.get();
          replacementMap.putAll(sourceMap);
          sourceMap = replacementMap;
       }
       catch(Exception e)
       {
-         throw (new IllegalStateException("The mutable type provided for this MutableMap [" + mutableTypeIfNeeded.getName() + "] could not be instantiated."));
+         throw (new IllegalStateException("Error getting from the supplier provided for this MutableMap.", e));
       }
    }
 

qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/collections/MutableListTest.java

@@ -22,9 +22,11 @@
 package com.kingsrook.qqq.backend.core.utils.collections;
 
 
+import java.util.LinkedList;
 import java.util.List;
 import com.kingsrook.qqq.backend.core.BaseTest;
 import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 
 /*******************************************************************************
@@ -48,4 +50,22 @@ class MutableListTest extends BaseTest
       list.remove(0);
    }
 
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Test
+   void testNullInput()
+   {
+      List<Integer> list = new MutableList<>(null);
+      list.add(1);
+      assertEquals(1, list.size());
+
+      MutableList<Integer> mutableList = new MutableList<>(null, LinkedList::new);
+      mutableList.add(1);
+      assertEquals(1, mutableList.size());
+      assertEquals(LinkedList.class, mutableList.getUnderlyingList().getClass());
+   }
+
 }

qqq-backend-core/src/test/java/com/kingsrook/qqq/backend/core/utils/collections/MutableMapTest.java

@@ -22,9 +22,11 @@
 package com.kingsrook.qqq.backend.core.utils.collections;
 
 
+import java.util.LinkedHashMap;
 import java.util.Map;
 import com.kingsrook.qqq.backend.core.BaseTest;
 import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 
 /*******************************************************************************
@@ -48,4 +50,22 @@ class MutableMapTest extends BaseTest
       map.putAll(Map.of("c", 3, "d", 4));
    }
 
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Test
+   void testNullInput()
+   {
+      Map<Integer, String> map = new MutableMap<>(null);
+      map.put(1, "one");
+      assertEquals(1, map.size());
+
+      MutableMap<Integer, String> mutableMap = new MutableMap<>(null, LinkedHashMap::new);
+      mutableMap.put(1, "uno");
+      assertEquals(1, mutableMap.size());
+      assertEquals(LinkedHashMap.class, mutableMap.getUnderlyingMap().getClass());
+   }
+
 }