From 4b7c2d43818a71e0c6975fcf3a1f1e0f1533ce3c Mon Sep 17 00:00:00 2001
From: Mark Hansen <markhansen@google.com>
Date: Fri, 10 May 2024 08:33:09 -0700
Subject: [PATCH] Avoid allocating TreeMap in UnknownFieldSet.Builder.asMap

If UnknownFieldSet is empty

PiperOrigin-RevId: 632504647
---
 .../src/main/java/com/google/protobuf/UnknownFieldSet.java   | 5 +++++
 1 file changed, 5 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 aa71004da75f..2c21c5479400 100644
--- a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
+++ b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -483,6 +483,11 @@ public Builder addField(int number, Field field) {
      * changes may or may not be reflected in this map.
      */
     public Map<Integer, Field> asMap() {
+      // Avoid an allocation for the common case of an empty map.
+      if (fieldBuilders.isEmpty()) {
+        return Collections.emptyMap();
+      }
+
       TreeMap<Integer, Field> fields = new TreeMap<>();
       for (Map.Entry<Integer, Field.Builder> entry : fieldBuilders.entrySet()) {
         fields.put(entry.getKey(), entry.getValue().build());