From 101dc3ea704d58a4ee172e40a73f40e5fb3cabe8 Mon Sep 17 00:00:00 2001
From: Near Privman <nearp@google.com>
Date: Tue, 23 Aug 2022 03:57:49 -0700
Subject: [PATCH] `collect`: Presize the `ImmutableMap` builder when
 `uniqueIndex` is run on a `Collection`

RELNOTES=`collect`: Presize the `ImmutableMap` builder when `uniqueIndex` is run on a `Collection`
PiperOrigin-RevId: 469418201
---
 .../guava/src/com/google/common/collect/Maps.java   | 13 +++++++++++--
 guava/src/com/google/common/collect/Maps.java       | 13 +++++++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/android/guava/src/com/google/common/collect/Maps.java b/android/guava/src/com/google/common/collect/Maps.java
index 6235f195eda5..de581ea4437d 100644
--- a/android/guava/src/com/google/common/collect/Maps.java
+++ b/android/guava/src/com/google/common/collect/Maps.java
@@ -1282,7 +1282,12 @@ public static <K, V> ImmutableMap<K, V> toMap(
   @CanIgnoreReturnValue
   public static <K, V> ImmutableMap<K, V> uniqueIndex(
       Iterable<V> values, Function<? super V, K> keyFunction) {
-    // TODO(lowasser): consider presizing the builder if values is a Collection
+    if (values instanceof Collection) {
+      return uniqueIndex(
+          values.iterator(),
+          keyFunction,
+          ImmutableMap.builderWithExpectedSize(((Collection<?>) values).size()));
+    }
     return uniqueIndex(values.iterator(), keyFunction);
   }
 
@@ -1318,8 +1323,12 @@ public static <K, V> ImmutableMap<K, V> uniqueIndex(
   @CanIgnoreReturnValue
   public static <K, V> ImmutableMap<K, V> uniqueIndex(
       Iterator<V> values, Function<? super V, K> keyFunction) {
+    return uniqueIndex(values, keyFunction, ImmutableMap.builder());
+  }
+
+  private static <K, V> ImmutableMap<K, V> uniqueIndex(
+      Iterator<V> values, Function<? super V, K> keyFunction, ImmutableMap.Builder<K, V> builder) {
     checkNotNull(keyFunction);
-    ImmutableMap.Builder<K, V> builder = ImmutableMap.builder();
     while (values.hasNext()) {
       V value = values.next();
       builder.put(keyFunction.apply(value), value);
diff --git a/guava/src/com/google/common/collect/Maps.java b/guava/src/com/google/common/collect/Maps.java
index 0754dbe332c5..c1517bc9727d 100644
--- a/guava/src/com/google/common/collect/Maps.java
+++ b/guava/src/com/google/common/collect/Maps.java
@@ -1358,7 +1358,12 @@ public static <K, V> ImmutableMap<K, V> toMap(
   @CanIgnoreReturnValue
   public static <K, V> ImmutableMap<K, V> uniqueIndex(
       Iterable<V> values, Function<? super V, K> keyFunction) {
-    // TODO(lowasser): consider presizing the builder if values is a Collection
+    if (values instanceof Collection) {
+      return uniqueIndex(
+          values.iterator(),
+          keyFunction,
+          ImmutableMap.builderWithExpectedSize(((Collection<?>) values).size()));
+    }
     return uniqueIndex(values.iterator(), keyFunction);
   }
 
@@ -1394,8 +1399,12 @@ public static <K, V> ImmutableMap<K, V> uniqueIndex(
   @CanIgnoreReturnValue
   public static <K, V> ImmutableMap<K, V> uniqueIndex(
       Iterator<V> values, Function<? super V, K> keyFunction) {
+    return uniqueIndex(values, keyFunction, ImmutableMap.builder());
+  }
+
+  private static <K, V> ImmutableMap<K, V> uniqueIndex(
+      Iterator<V> values, Function<? super V, K> keyFunction, ImmutableMap.Builder<K, V> builder) {
     checkNotNull(keyFunction);
-    ImmutableMap.Builder<K, V> builder = ImmutableMap.builder();
     while (values.hasNext()) {
       V value = values.next();
       builder.put(keyFunction.apply(value), value);