Java full runtime: Avoid allocating when calling asMap on empty UnknownFieldSet

mhansen · copybara-github · commit d0b016fcfcd0 · 2024-05-06T17:28:34.000-07:00
PiperOrigin-RevId: 631235442
diff --git a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -85,6 +85,10 @@ public int hashCode() {
 
   /** Get a map of fields in the set by number. */
   public Map<Integer, Field> asMap() {
+    // Avoid an allocation for the common case of an empty map.
+    if (fields.isEmpty()) {
+      return Collections.emptyMap();
+    }
     return (Map<Integer, Field>) fields.clone();
   }
 

Original file line number	Diff line number	Diff line change
`@@ -85,6 +85,10 @@ public int hashCode() {`
`85`	`85`
`86`	`86`	`/** Get a map of fields in the set by number. */`
`87`	`87`	`public Map<Integer, Field> asMap() {`
	`88`	`+ // Avoid an allocation for the common case of an empty map.`
	`89`	`+ if (fields.isEmpty()) {`
	`90`	`+ return Collections.emptyMap();`
	`91`	`+ }`
`88`	`92`	`return (Map<Integer, Field>) fields.clone();`
`89`	`93`	`}`
`90`	`94`