Observable javadoc: the condition is inverted between takeWhile and takeUntil.

ePaul · web-flow · commit 20bc4b61ae58 · 2025-04-14T18:12:23.000+02:00
The current description of the difference between takeWhile and takeUntil just points to the evaluation time (before or after the element is emitted), but the (IMHO) more important fact is that the predicate is inverted between both: one emits just elements where the predicate is true, the other just elements where the predicate is false (and the first true one).
diff --git a/src/main/java/io/reactivex/rxjava3/core/Observable.java b/src/main/java/io/reactivex/rxjava3/core/Observable.java
@@ -14147,7 +14147,7 @@ public final Observable<T> takeLast(long time, @NonNull TimeUnit unit, @NonNull
      * <img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeUntil.p.v3.png" alt="">
      * <p>
      * The difference between this operator and {@link #takeWhile(Predicate)} is that here, the condition is
-     * evaluated <em>after</em> the item is emitted.
+     * evaluated <em>after</em> the item is emitted. (Also, the condition is inverted.)
      *
      * <dl>
      *  <dt><b>Scheduler:</b></dt>

Original file line number	Diff line number	Diff line change
`@@ -14147,7 +14147,7 @@ public final Observable<T> takeLast(long time, @NonNull TimeUnit unit, @NonNull`
`14147`	`14147`	`* <img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeUntil.p.v3.png" alt="">`
`14148`	`14148`	`* <p>`
`14149`	`14149`	`* The difference between this operator and {@link #takeWhile(Predicate)} is that here, the condition is`
`14150`		`- * evaluated <em>after</em> the item is emitted.`
	`14150`	`+ * evaluated <em>after</em> the item is emitted. (Also, the condition is inverted.)`
`14151`	`14151`	`*`
`14152`	`14152`	`* <dl>`
`14153`	`14153`	`* <dt><b>Scheduler:</b></dt>`