Add getFirst(K key) and getLast(K key) methods to ListOperations.

Original pull request: #2966
Closes #2937

Author: violetbeach

src/main/java/org/springframework/data/redis/core/ListOperations.java

@@ -34,6 +34,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author dengliming
+ * @author Lee Jaeheon
  */
 public interface ListOperations<K, V> {
 
@@ -559,5 +560,35 @@ default V rightPopAndLeftPush(K sourceKey, K destinationKey, Duration timeout) {
 		return rightPopAndLeftPush(sourceKey, destinationKey, TimeoutUtils.toSeconds(timeout), TimeUnit.SECONDS);
 	}
 
+	/**
+	 * Returns the first element from list at {@code key}.
+	 *
+	 * @implSpec
+	 * The implementation in this interface returns the result of calling {@code index(key, 0)}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return {@literal null} when used in pipeline / transaction.
+	 */
+	@Nullable
+	default V getFirst(K key) {
+		return index(key, 0);
+	}
+
+	/**
+	 * Returns the last element from list at {@code key}.
+	 *
+	 * @implSpec
+	 * If the result of calling {@code size(key)} is not null, The implementation in this interface returns the
+	 * result of calling {@code index(key, size - 1)}. Otherwise, it returns null.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return {@literal null} when used in pipeline / transaction.
+	 */
+	@Nullable
+	default V getLast(K key) {
+		Long size = size(key);
+		return size != null ? index(key, size - 1) : null;
+	}
+
 	RedisOperations<K, V> getOperations();
 }

src/test/java/org/springframework/data/redis/core/DefaultListOperationsIntegrationIntegrationTests.java

@@ -40,6 +40,7 @@
  * @author Jennifer Hickey
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Lee Jaeheon
  * @param <K> Key test
  * @param <V> Value test
  */
@@ -376,4 +377,32 @@ void lastIndexOf() {
 		assertThat(listOps.rightPush(key, v3)).isEqualTo(Long.valueOf(4));
 		assertThat(listOps.lastIndexOf(key, v1)).isEqualTo(2);
 	}
+
+	@ParameterizedRedisTest // GH-2937
+	void getFirst() {
+
+		K key = keyFactory.instance();
+		V v1 = valueFactory.instance();
+		V v2 = valueFactory.instance();
+		V v3 = valueFactory.instance();
+
+		listOps.rightPush(key, v1);
+		listOps.rightPush(key, v2);
+		listOps.rightPush(key, v3);
+		assertThat(listOps.getFirst(key)).isEqualTo(v1);
+	}
+
+	@ParameterizedRedisTest // GH-2937
+	void getLast() {
+
+		K key = keyFactory.instance();
+		V v1 = valueFactory.instance();
+		V v2 = valueFactory.instance();
+		V v3 = valueFactory.instance();
+
+		listOps.rightPush(key, v1);
+		listOps.rightPush(key, v2);
+		listOps.rightPush(key, v3);
+		assertThat(listOps.getLast(key)).isEqualTo(v3);
+	}
 }