RFR: JDK-8062849 -- Optimize EnumMap.equals

[Steve Drach]

Please review the following simple fix for the issue reported in https://bugs.openjdk.java.net/browse/JDK-8062849 <https://bugs.openjdk.java.net/browse/JDK-8062849>.

-----------------
# HG changeset patch
# User sdrach
# Date 1437777193 25200
#      Fri Jul 24 15:33:13 2015 -0700
# Node ID e57b1569a65ec4dc8c749dedd3345abe5d493054
# Parent  4dd09cb5f7c2a2a23a9958ea7a602dd74d5709b2
8062849: Optimize EnumMap.equals
Summary: In the equals method, if the two EnumMaps are a different size return false since they can't be equal.
Reviewed-by: brent.christian at oracle.com, paul.sandoz at oracle.com
Contributed-by: steve.drach at oracle.com

diff --git a/src/java.base/share/classes/java/util/EnumMap.java b/src/java.base/share/classes/java/util/EnumMap.java
--- a/src/java.base/share/classes/java/util/EnumMap.java
+++ b/src/java.base/share/classes/java/util/EnumMap.java
@@ -681,8 +681,11 @@
     }
 
     private boolean equals(EnumMap<?,?> em) {
+        if (size != em.size)
+            return false;
+
         if (em.keyType != keyType)
-            return size == 0 && em.size == 0;
+            return size == 0;
 
         // Key types match, compare each value
         for (int i = 0; i < keyUniverse.length; i++) {