Merge pull request #142 from dfa1/presize-result-loadMany

Pre-size resulting lists

Author: bbakerman

src/main/java/org/dataloader/BatchLoaderEnvironment.java

@@ -83,7 +83,7 @@ public <K> Builder keyContexts(List<K> keys, List<Object> keyContexts) {
             Assertions.nonNull(keyContexts);
 
             Map<Object, Object> map = new HashMap<>();
-            List<Object> list = new ArrayList<>();
+            List<Object> list = new ArrayList<>(keys.size());
             for (int i = 0; i < keys.size(); i++) {
                 K key = keys.get(i);
                 Object keyContext = null;

src/main/java/org/dataloader/DataLoader.java

@@ -561,7 +561,7 @@ public CompletableFuture<List<V>> loadMany(List<K> keys, List<Object> keyContext
         nonNull(keyContexts);
 
         synchronized (this) {
-            List<CompletableFuture<V>> collect = new ArrayList<>();
+            List<CompletableFuture<V>> collect = new ArrayList<>(keys.size());
             for (int i = 0; i < keys.size(); i++) {
                 K key = keys.get(i);
                 Object keyContext = null;

src/main/java/org/dataloader/DataLoaderHelper.java

@@ -213,9 +213,9 @@ DispatchResult<V> dispatch() {
     private CompletableFuture<List<V>> sliceIntoBatchesOfBatches(List<K> keys, List<CompletableFuture<V>> queuedFutures, List<Object> callContexts, int maxBatchSize) {
         // the number of keys is > than what the batch loader function can accept
         // so make multiple calls to the loader
-        List<CompletableFuture<List<V>>> allBatches = new ArrayList<>();
         int len = keys.size();
         int batchCount = (int) Math.ceil(len / (double) maxBatchSize);
+        List<CompletableFuture<List<V>>> allBatches = new ArrayList<>(batchCount);
         for (int i = 0; i < batchCount; i++) {
 
             int fromIndex = i * maxBatchSize;
@@ -477,7 +477,7 @@ private CompletableFuture<List<V>> invokeMapBatchLoader(List<K> keys, BatchLoade
         }
         CompletableFuture<Map<K, V>> mapBatchLoad = nonNull(loadResult, () -> "Your batch loader function MUST return a non null CompletionStage").toCompletableFuture();
         return mapBatchLoad.thenApply(map -> {
-            List<V> values = new ArrayList<>();
+            List<V> values = new ArrayList<>(keys.size());
             for (K key : keys) {
                 V value = map.get(key);
                 values.add(value);

src/main/java/org/dataloader/ValueCache.java

@@ -115,7 +115,7 @@ default CompletableFuture<List<Try<V>>> getValues(List<K> keys) throws ValueCach
      * @throws ValueCachingNotSupported if this cache wants to short-circuit this method completely
      */
     default CompletableFuture<List<V>> setValues(List<K> keys, List<V> values) throws ValueCachingNotSupported {
-        List<CompletableFuture<V>> cacheSets = new ArrayList<>();
+        List<CompletableFuture<V>> cacheSets = new ArrayList<>(keys.size());
         for (int i = 0; i < keys.size(); i++) {
             K k = keys.get(i);
             V v = values.get(i);