collect: Presize the ImmutableMap builder when uniqueIndex is r…

…un on a `Collection` RELNOTES=`collect`: Presize the `ImmutableMap` builder when `uniqueIndex` is run on a `Collection` PiperOrigin-RevId: 469418201
google · Aug 23, 2022 · 101dc3e · 101dc3e
1 parent 4312d94
commit 101dc3e
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git 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
@@ -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);