[GitHub] [wicket] astange1 commented on a diff in pull request #513: More efficient hashcode computations

[GitBox <gi...@apache.org>]

astange1 commented on code in PR #513:
URL: https://github.com/apache/wicket/pull/513#discussion_r853408043


##########
wicket-core/src/main/java/org/apache/wicket/markup/head/AbstractJavaScriptReferenceHeaderItem.java:
##########
@@ -135,6 +135,16 @@ public boolean equals(Object o)
 	@Override
 	public int hashCode()
 	{
-		return Objects.hash(async, defer, charset);
+		// original code was: return Objects.hash(async, defer, charset);
+		// This returns the same hash code value, but doesn't allocate an Object[3],
+		// which consumes 32 bytes, and doesn't need to autobox the two booleans.
+		// This method is called very often, especially when a containing Map or Set is resized,
+		// and this version will run faster and save a lot of memory.
+		// It is possible that Escape Analysis would elide the creation of the Object[],
+		// but we do not see that in our running applications with the latest JDK.
+		return 31*31*31 +
+				31*31*Boolean.hashCode(async) +
+				31*Boolean.hashCode(defer) +
+				((charset != null) ? charset.hashCode() : 0);

Review Comment:
   I wrote it the original way to produce the exact same hashcode value as the original code, and to minimize the math being done.    Are we OK with the hashcode values being different, perhaps resulting in other changes due to hashing?
   
   I will update the CSSHeaderItem classes, and also remove the comments. 



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: commits-unsubscribe@wicket.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org