[jOOQ#305] added ArrayList initialization based on source.estimateSize()

src/main/java/org/jooq/lambda/SeqBuffer.java

@@ -18,6 +18,11 @@
  */
 final class SeqBuffer<T> {
 
+    /**
+     * @see ArrayList#MAX_ARRAY_SIZE
+     */
+    private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
     @SuppressWarnings("unchecked")
     static <T> SeqBuffer<T> of(Stream<? extends T> stream) {
         return of((Spliterator<T>) stream.spliterator());
@@ -31,7 +36,7 @@ static <T> SeqBuffer<T> of(Spliterator<T> spliterator) {
     }
 
     private final Spliterator<T> source;
-    private final List<T> buffer = new ArrayList<>();
+    private final List<T> buffer;
 
     /**
      * <code>True</code> while <code>source</code> hasn't reported that it's exhausted.
@@ -44,6 +49,7 @@ static <T> SeqBuffer<T> of(Spliterator<T> spliterator) {
 
     private SeqBuffer(Spliterator<T> source) {
         this.source = Objects.requireNonNull(source);
+        this.buffer = initBuffer(source);
     }
 
     /**
@@ -57,6 +63,17 @@ Seq<T> seq() {
         return Seq.seq(new BufferSpliterator());
     }
 
+    private static <T> List<T> initBuffer(Spliterator<T> source) {
+        long estimateSize = source.estimateSize();
+        if (estimateSize == Long.MAX_VALUE) // infinite/unknown size
+            return new ArrayList<>();
+
+        if (estimateSize > MAX_ARRAY_SIZE)
+            throw new IllegalArgumentException("Stream is too long to be buffered: " + estimateSize);
+
+        return new ArrayList<>((int) estimateSize);
+    }
+
     /**
      * Special <code>Spliterator</code> whose <code>tryAdvance</code> method can buffer
      * (i.e. can advance the <code>source</code> spliterator).