--- jsr166/src/main/java/util/HashMap.java	2018/03/28 02:50:41	1.4
+++ jsr166/src/main/java/util/HashMap.java	2018/08/10 19:35:20	1.7
@@ -376,12 +376,7 @@ public class HashMap<K,V> extends Abstra
      * Returns a power of two size for the given target capacity.
      */
     static final int tableSizeFor(int cap) {
-        int n = cap - 1;
-        n |= n >>> 1;
-        n |= n >>> 2;
-        n |= n >>> 4;
-        n |= n >>> 8;
-        n |= n >>> 16;
+        int n = -1 >>> Integer.numberOfLeadingZeros(cap - 1);
         return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
     }
 
@@ -1268,9 +1263,7 @@ public class HashMap<K,V> extends Abstra
     @Override
     public V merge(K key, V value,
                    BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
-        if (value == null)
-            throw new NullPointerException();
-        if (remappingFunction == null)
+        if (value == null || remappingFunction == null)
             throw new NullPointerException();
         int hash = hash(key);
         Node<K,V>[] tab; Node<K,V> first; int n, i;
@@ -1313,8 +1306,7 @@ public class HashMap<K,V> extends Abstra
             else
                 removeNode(hash, key, null, false, true);
             return v;
-        }
-        if (value != null) {
+        } else {
             if (t != null)
                 t.putTreeVal(this, tab, hash, key, value);
             else {
@@ -1325,8 +1317,8 @@ public class HashMap<K,V> extends Abstra
             ++modCount;
             ++size;
             afterNodeInsertion(true);
+            return value;
         }
-        return value;
     }
 
     @Override
@@ -2153,7 +2145,7 @@ public class HashMap<K,V> extends Abstra
             if (replacement != p) {
                 TreeNode<K,V> pp = replacement.parent = p.parent;
                 if (pp == null)
-                    root = replacement;
+                    (root = replacement).red = false;
                 else if (p == pp.left)
                     pp.left = replacement;
                 else