From e66890a6d2b19f54fa6fd2eec7ef6339e79a9e32 Mon Sep 17 00:00:00 2001
From: Anton Makeev <Anton.Makeev@jetbrains.com>
Date: Wed, 29 Aug 2018 17:37:07 +0200
Subject: [PATCH] ContainerUtil.unmodifiableOrEmpty* methods optimized for
 1-element collections

---
 .../com/intellij/util/containers/ContainerUtil.java | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/platform/util/src/com/intellij/util/containers/ContainerUtil.java b/platform/util/src/com/intellij/util/containers/ContainerUtil.java
index cf769c324380..c10a9426670f 100644
--- a/platform/util/src/com/intellij/util/containers/ContainerUtil.java
+++ b/platform/util/src/com/intellij/util/containers/ContainerUtil.java
@@ -212,6 +212,9 @@ public class ContainerUtil extends ContainerUtilRt {
     if (size == 0) {
       return emptyList();
     }
+    if (size == 1) {
+      return Collections.singletonList(original.iterator().next());
+    }
     else {
       return Collections.unmodifiableCollection(original);
     }
@@ -224,6 +227,9 @@ public class ContainerUtil extends ContainerUtilRt {
     if (size == 0) {
       return emptyList();
     }
+    if (size == 1) {
+      return Collections.singletonList(original.iterator().next());
+    }
     else {
       return Collections.unmodifiableList(original);
     }
@@ -236,6 +242,9 @@ public class ContainerUtil extends ContainerUtilRt {
     if (size == 0) {
       return Collections.emptySet();
     }
+    if (size == 1) {
+      return Collections.singleton(original.iterator().next());
+    }
     else {
       return Collections.unmodifiableSet(original);
     }
@@ -248,6 +257,10 @@ public class ContainerUtil extends ContainerUtilRt {
     if (size == 0) {
       return Collections.emptyMap();
     }
+    if (size == 1) {
+      Map.Entry<? extends K, ? extends V> entry = original.entrySet().iterator().next();
+      return Collections.singletonMap(entry.getKey(), entry.getValue());
+    }
     else {
       return Collections.unmodifiableMap(original);
     }