From 23cbb2d1709b5e7509e373d4642806d6436cbbcb Mon Sep 17 00:00:00 2001
From: Christoph Dreis <christoph.dreis@freenet.de>
Date: Tue, 16 May 2023 14:22:40 +0000
Subject: [PATCH] 8306860: Avoid unnecessary allocation in List.map() when list
 is empty

Reviewed-by: vromero
---
 .../share/classes/com/sun/tools/javac/util/List.java           | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/util/List.java b/src/jdk.compiler/share/classes/com/sun/tools/javac/util/List.java
index fb295ee0f6c..ceb5614ed0f 100644
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/util/List.java
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/util/List.java
@@ -419,6 +419,9 @@ public class List<A> extends AbstractCollection<A> implements java.util.List<A>
 
     @SuppressWarnings("unchecked")
     public <Z> List<Z> map(Function<A, Z> mapper) {
+        if (isEmpty()) {
+            return (List<Z>)this;
+        }
         boolean changed = false;
         ListBuffer<Z> buf = new ListBuffer<>();
         for (A a : this) {