Remove duplicate code in DefaultRedisList.

Closes: spring-projects#2996 Original pull request: spring-projects#2997

Author: jinbeom

src/main/java/org/springframework/data/redis/support/collections/DefaultRedisList.java

@@ -41,6 +41,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author John Blum
+ * @author Jinbeom Kim
  */
 public class DefaultRedisList<E> extends AbstractRedisCollection<E> implements RedisList<E> {
 
@@ -216,16 +217,14 @@ public boolean remove(Object o) {
 public void add(int index, E element) {
 
 if (index == 0) {
-listOps.leftPush(element);
-cap();
+addFirst(element);
 return;
 }
 
 int size = size();
 
 if (index == size()) {
-listOps.rightPush(element);
-cap();
+addLast(element);
 return;
 }
 
@@ -241,24 +240,15 @@ public boolean addAll(int index, Collection<? extends E> collection) {
 
 // insert collection in reverse
 if (index == 0) {
-
-Collection<? extends E> reverseCollection = CollectionUtils.reverse(collection);
-
-for (E element : reverseCollection) {
-listOps.leftPush(element);
-cap();
-}
-
+CollectionUtils.reverse(collection)
+.forEach(this::addFirst);
 return true;
 }
 
 int size = size();
 
 if (index == size()) {
-for (E element : collection) {
-listOps.rightPush(element);
-cap();
-}
+collection.forEach(this::addLast);
 return true;
 }
 
@@ -341,9 +331,7 @@ public E element() {
 
 @Override
 public boolean offer(E element) {
-listOps.rightPush(element);
-cap();
-return true;
+return add(element);
 }
 
 @Override