Extract duplicate duration validation logic to helper method

- Add isPositiveDuration(Duration) helper method
- Replace duplicate validation logic at lines 215 and 566
- Improve code maintainability and readability

Signed-off-by: bread <thayer2392@gmail.com>

Author: youngsuk-kim

src/main/java/org/springframework/data/redis/cache/DefaultRedisCacheWriter.java

@@ -212,7 +212,7 @@ public void enable(Consumer<CacheLockingConfiguration> configurationConsumer) {
 		public CacheLockingConfiguration sleepTime(Duration sleepTime) {
 
 			Assert.notNull(sleepTime, "Lock sleep time must not be null");
-			Assert.isTrue(!sleepTime.isZero() && !sleepTime.isNegative(),
+			Assert.isTrue(isPositiveDuration(sleepTime),
 					"Lock sleep time must not be null zero or negative");
 
 			this.lockSleepTime = sleepTime;
@@ -563,7 +563,7 @@ private <T> T executeLockFree(Function<RedisConnection, T> callback) {
 	 * @return {@literal true} if {@link RedisCacheWriter} uses locks.
 	 */
 	private boolean isLockingCacheWriter() {
-		return !this.sleepTime.isZero() && !this.sleepTime.isNegative();
+		return isPositiveDuration(this.sleepTime);
 	}
 
 	private void checkAndPotentiallyWaitUntilUnlocked(String name, RedisConnection connection) {
@@ -601,6 +601,10 @@ private static boolean shouldExpireWithin(@Nullable Duration ttl) {
 		return ttl != null && !ttl.isZero() && !ttl.isNegative();
 	}
 
+	private static boolean isPositiveDuration(Duration duration) {
+		return !duration.isZero() && !duration.isNegative();
+	}
+
 	/**
 	 * Interface for asynchronous cache retrieval.
 	 *