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Merged
bbakerman merged 1 commit into from
Jun 8, 2022
Merged

ImmutableKit.map with pre-size #2841

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17 changes: 10 additions & 7 deletions src/main/java/graphql/collect/ImmutableKit.java
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Original file line number Diff line number Diff line change
Expand Up @@ -61,26 +61,27 @@ public static <K, V> ImmutableMap<K, V> mergeMaps(Map<K, V> m1, Map<K, V> m2) {
}

public static <T> ImmutableList<T> concatLists(List<T> l1, List<T> l2) {
return ImmutableList.<T>builder().addAll(l1).addAll(l2).build();
//noinspection UnstableApiUsage
return ImmutableList.<T>builderWithExpectedSize(l1.size() + l2.size()).addAll(l1).addAll(l2).build();
}

/**
* This is more efficient than `c.stream().map().collect()` because it does not create the intermediate objects needed
* for the flexible style. Benchmarking has shown this to outperform `stream()`.
*
* @param iterable the iterable to map
* @param collection the collection to map
* @param mapper the mapper function
* @param <T> for two
* @param <R> for result
*
* @return a map immutable list of results
*/
public static <T, R> ImmutableList<R> map(Iterable<? extends T> iterable, Function<? super T, ? extends R> mapper) {
assertNotNull(iterable);
public static <T, R> ImmutableList<R> map(Collection<? extends T> collection, Function<? super T, ? extends R> mapper) {
assertNotNull(collection);
assertNotNull(mapper);
@SuppressWarnings("RedundantTypeArguments")
ImmutableList.Builder<R> builder = ImmutableList.<R>builder();
for (T t : iterable) {
@SuppressWarnings({"RedundantTypeArguments", "UnstableApiUsage"})
ImmutableList.Builder<R> builder = ImmutableList.<R>builderWithExpectedSize(collection.size());
for (T t : collection) {
R r = mapper.apply(t);
builder.add(r);
}
Expand All @@ -101,6 +102,7 @@ public static <T> ImmutableList<T> addToList(Collection<? extends T> existing, T
assertNotNull(existing);
assertNotNull(newValue);
int expectedSize = existing.size() + 1 + extraValues.length;
@SuppressWarnings("UnstableApiUsage")
ImmutableList.Builder<T> newList = ImmutableList.builderWithExpectedSize(expectedSize);
newList.addAll(existing);
newList.add(newValue);
Expand All @@ -124,6 +126,7 @@ public static <T> ImmutableSet<T> addToSet(Collection<? extends T> existing, T n
assertNotNull(existing);
assertNotNull(newValue);
int expectedSize = existing.size() + 1 + extraValues.length;
@SuppressWarnings("UnstableApiUsage")
ImmutableSet.Builder<T> newSet = ImmutableSet.builderWithExpectedSize(expectedSize);
newSet.addAll(existing);
newSet.add(newValue);
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2 changes: 1 addition & 1 deletion src/test/java/benchmark/ListBenchmark.java
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Expand Up @@ -33,7 +33,7 @@ private static List<String> buildStartingList() {
return list;
}

Function<String, String> mapper = s -> new StringBuilder(s).reverse().toString();
private final Function<String, String> mapper = s -> new StringBuilder(s).reverse().toString();

@Benchmark
public void benchmarkListStream(Blackhole blackhole) {
Expand Down