From d0b016fcfcd00a0e48d006f06868b8fb9876974a Mon Sep 17 00:00:00 2001
From: Mark Hansen <markhansen@google.com>
Date: Mon, 6 May 2024 17:26:29 -0700
Subject: [PATCH] Java full runtime: Avoid allocating when calling asMap on
 empty UnknownFieldSet

PiperOrigin-RevId: 631235442
---
 .../src/main/java/com/google/protobuf/UnknownFieldSet.java    | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
index 38aecac42f49..b93e22033323 100644
--- 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();
   }