Document behavior for 0 delay combined with jitter

Closes gh-36946

framework-docs/modules/ROOT/pages/core/resilience.adoc

@@ -81,6 +81,13 @@ public void sendNotification() {
 }
 ----
 
+[NOTE]
+====
+When `delay` is `0` combined with a positive `jitter`, the delay never grows
+regardless of any configured `multiplier`, so the full configured `jitter` is
+applied directly as a random delay in the range from `0` to `min(jitter, maxDelay)`.
+====
+
 Last but not least, `@Retryable` also works for reactive methods with a reactive return
 type, decorating the pipeline with Reactor's retry capabilities:
 
@@ -263,6 +270,13 @@ and an exponential back-off strategy with a bit of jitter.
             () -> jmsClient.destination("notifications").send(...));
 ----
 
+[NOTE]
+====
+When `delay` is zero combined with a positive `jitter`, the delay never grows
+regardless of any configured `multiplier`, so the full configured `jitter` is
+applied directly as a random delay in the range from zero to `min(jitter, maxDelay)`.
+====
+
 [TIP]
 ====
 Although the factory methods and builder API for `RetryPolicy` cover most common

spring-context/src/main/java/org/springframework/resilience/annotation/Retryable.java

@@ -197,6 +197,10 @@ public @interface Retryable {
 	 * and {@code delay + jitter} but never below the base {@link #delay()} or
 	 * above {@link #maxDelay()}. If a multiplier is specified, it is applied
 	 * to the jitter value as well.
+	 * <p>When {@link #delay()} is {@code 0} combined with a positive jitter,
+	 * the delay never grows regardless of any configured multiplier, so the
+	 * full configured jitter is applied directly as a random delay in the range
+	 * from {@code 0} to {@code min(jitter, maxDelay)}.
 	 * <p>The time unit is milliseconds by default but can be overridden via
 	 * {@link #timeUnit}.
 	 * <p>The default is 0 (no jitter).

spring-core/src/main/java/org/springframework/core/retry/RetryPolicy.java

@@ -281,6 +281,11 @@ public interface RetryPolicy {
 		 * {@linkplain #maxDelay(Duration) max delay}.
 		 * <p>If a {@linkplain #multiplier(double) multiplier} is specified, it
 		 * is applied to the jitter value as well.
+		 * <p>When the configured {@linkplain #delay(Duration) delay} is zero
+		 * combined with a positive jitter, the delay never grows regardless of
+		 * any configured multiplier, so the full configured jitter is applied
+		 * directly as a random delay in the range from zero to
+		 * {@code min(jitter, maxDelay)}.
 		 * <p>The default is no jitter.
 		 * <p>The supplied value will override any previously configured value.
 		 * <p>You should not specify this configuration option if you have

spring-core/src/main/java/org/springframework/util/backoff/ExponentialBackOff.java

@@ -154,6 +154,10 @@ public class ExponentialBackOff implements BackOff {
 	 * {@code initialInterval} or above {@code maxInterval}.
 	 * <p>If a {@code multiplier} is specified, it is applied to the jitter value
 	 * as well.
+	 * <p>When {@code initialInterval} is {@code 0} combined with a positive
+	 * jitter, the interval never grows regardless of any configured multiplier,
+	 * so the full configured jitter is applied directly as a random interval in
+	 * the range from {@code 0} to {@code min(jitter, maxInterval)}.
 	 * @param jitter the jitter value in milliseconds
 	 * @since 7.0
 	 */