From b3d7f5f2ac25344143ebdf22f4ae23677e41cc8f Mon Sep 17 00:00:00 2001
From: Lorenz Pahl <l.pahl@outlook.com>
Date: Thu, 21 Mar 2019 14:00:27 +0100
Subject: [PATCH] Make error messages of parameter checks consistent (#6433)

---
 src/main/java/io/reactivex/Completable.java |   2 +-
 src/main/java/io/reactivex/Flowable.java    | 126 +++++++++----------
 src/main/java/io/reactivex/Maybe.java       |  10 +-
 src/main/java/io/reactivex/Observable.java  | 131 ++++++++++----------
 src/main/java/io/reactivex/Single.java      |  10 +-
 5 files changed, 139 insertions(+), 140 deletions(-)

diff --git a/src/main/java/io/reactivex/Completable.java b/src/main/java/io/reactivex/Completable.java
index 7ac7ead344..13364dc1a6 100644
--- a/src/main/java/io/reactivex/Completable.java
+++ b/src/main/java/io/reactivex/Completable.java
@@ -2292,7 +2292,7 @@ public final Disposable subscribe() {
     @SchedulerSupport(SchedulerSupport.NONE)
     @Override
     public final void subscribe(CompletableObserver observer) {
-        ObjectHelper.requireNonNull(observer, "s is null");
+        ObjectHelper.requireNonNull(observer, "observer is null");
         try {
 
             observer = RxJavaPlugins.onSubscribe(this, observer);
diff --git a/src/main/java/io/reactivex/Flowable.java b/src/main/java/io/reactivex/Flowable.java
index 79f4251ddd..ff85859f99 100644
--- a/src/main/java/io/reactivex/Flowable.java
+++ b/src/main/java/io/reactivex/Flowable.java
@@ -1900,7 +1900,7 @@ public static <T> Flowable<T> empty() {
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> error(Callable<? extends Throwable> supplier) {
-        ObjectHelper.requireNonNull(supplier, "errorSupplier is null");
+        ObjectHelper.requireNonNull(supplier, "supplier is null");
         return RxJavaPlugins.onAssembly(new FlowableError<T>(supplier));
     }
 
@@ -2235,7 +2235,7 @@ public static <T> Flowable<T> fromPublisher(final Publisher<? extends T> source)
         if (source instanceof Flowable) {
             return RxJavaPlugins.onAssembly((Flowable<T>)source);
         }
-        ObjectHelper.requireNonNull(source, "publisher is null");
+        ObjectHelper.requireNonNull(source, "source is null");
 
         return RxJavaPlugins.onAssembly(new FlowableFromPublisher<T>(source));
     }
@@ -2662,8 +2662,8 @@ public static <T> Flowable<T> just(T item) {
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
 
         return fromArray(item1, item2);
     }
@@ -2696,9 +2696,9 @@ public static <T> Flowable<T> just(T item1, T item2) {
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
 
         return fromArray(item1, item2, item3);
     }
@@ -2733,10 +2733,10 @@ public static <T> Flowable<T> just(T item1, T item2, T item3) {
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
 
         return fromArray(item1, item2, item3, item4);
     }
@@ -2773,11 +2773,11 @@ public static <T> Flowable<T> just(T item1, T item2, T item3, T item4) {
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
 
         return fromArray(item1, item2, item3, item4, item5);
     }
@@ -2816,12 +2816,12 @@ public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5)
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5, T item6) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6);
     }
@@ -2862,13 +2862,13 @@ public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5,
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7);
     }
@@ -2911,14 +2911,14 @@ public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5,
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
-        ObjectHelper.requireNonNull(item8, "The eighth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
+        ObjectHelper.requireNonNull(item8, "item8 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7, item8);
     }
@@ -2963,15 +2963,15 @@ public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5,
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8, T item9) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
-        ObjectHelper.requireNonNull(item8, "The eighth item is null");
-        ObjectHelper.requireNonNull(item9, "The ninth is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
+        ObjectHelper.requireNonNull(item8, "item8 is null");
+        ObjectHelper.requireNonNull(item9, "item9 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7, item8, item9);
     }
@@ -3018,16 +3018,16 @@ public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5,
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Flowable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8, T item9, T item10) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
-        ObjectHelper.requireNonNull(item8, "The eighth item is null");
-        ObjectHelper.requireNonNull(item9, "The ninth item is null");
-        ObjectHelper.requireNonNull(item10, "The tenth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
+        ObjectHelper.requireNonNull(item8, "item8 is null");
+        ObjectHelper.requireNonNull(item9, "item9 is null");
+        ObjectHelper.requireNonNull(item10, "item10 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7, item8, item9, item10);
     }
@@ -4485,7 +4485,7 @@ public static <T, D> Flowable<T> using(Callable<? extends D> resourceSupplier,
                     Consumer<? super D> resourceDisposer, boolean eager) {
         ObjectHelper.requireNonNull(resourceSupplier, "resourceSupplier is null");
         ObjectHelper.requireNonNull(sourceSupplier, "sourceSupplier is null");
-        ObjectHelper.requireNonNull(resourceDisposer, "disposer is null");
+        ObjectHelper.requireNonNull(resourceDisposer, "resourceDisposer is null");
         return RxJavaPlugins.onAssembly(new FlowableUsing<T, D>(resourceSupplier, sourceSupplier, resourceDisposer, eager));
     }
 
@@ -8338,7 +8338,7 @@ public final Flowable<T> debounce(long timeout, TimeUnit unit, Scheduler schedul
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Flowable<T> defaultIfEmpty(T defaultItem) {
-        ObjectHelper.requireNonNull(defaultItem, "item is null");
+        ObjectHelper.requireNonNull(defaultItem, "defaultItem is null");
         return switchIfEmpty(just(defaultItem));
     }
 
@@ -9167,7 +9167,7 @@ private Flowable<T> doOnEach(Consumer<? super T> onNext, Consumer<? super Throwa
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Flowable<T> doOnEach(final Consumer<? super Notification<T>> onNotification) {
-        ObjectHelper.requireNonNull(onNotification, "consumer is null");
+        ObjectHelper.requireNonNull(onNotification, "onNotification is null");
         return doOnEach(
                 Functions.notificationOnNext(onNotification),
                 Functions.notificationOnError(onNotification),
@@ -11769,7 +11769,7 @@ public final Flowable<T> onBackpressureBuffer(int capacity, boolean delayError)
     @BackpressureSupport(BackpressureKind.SPECIAL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Flowable<T> onBackpressureBuffer(int capacity, boolean delayError, boolean unbounded) {
-        ObjectHelper.verifyPositive(capacity, "bufferSize");
+        ObjectHelper.verifyPositive(capacity, "capacity");
         return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBuffer<T>(this, capacity, unbounded, delayError, Functions.EMPTY_ACTION));
     }
 
@@ -11877,7 +11877,7 @@ public final Flowable<T> onBackpressureBuffer(int capacity, Action onOverflow) {
     @BackpressureSupport(BackpressureKind.SPECIAL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Flowable<T> onBackpressureBuffer(long capacity, Action onOverflow, BackpressureOverflowStrategy overflowStrategy) {
-        ObjectHelper.requireNonNull(overflowStrategy, "strategy is null");
+        ObjectHelper.requireNonNull(overflowStrategy, "overflowStrategy is null");
         ObjectHelper.verifyPositive(capacity, "capacity");
         return RxJavaPlugins.onAssembly(new FlowableOnBackpressureBufferStrategy<T>(this, capacity, onOverflow, overflowStrategy));
     }
@@ -13882,7 +13882,7 @@ public final Flowable<T> scan(BiFunction<T, T, T> accumulator) {
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Flowable<R> scan(final R initialValue, BiFunction<R, ? super T, R> accumulator) {
-        ObjectHelper.requireNonNull(initialValue, "seed is null");
+        ObjectHelper.requireNonNull(initialValue, "initialValue is null");
         return scanWith(Functions.justCallable(initialValue), accumulator);
     }
 
@@ -14562,7 +14562,7 @@ public final Flowable<T> startWith(Publisher<? extends T> other) {
     @BackpressureSupport(BackpressureKind.FULL)
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Flowable<T> startWith(T value) {
-        ObjectHelper.requireNonNull(value, "item is null");
+        ObjectHelper.requireNonNull(value, "value is null");
         return concatArray(just(value), this);
     }
 
diff --git a/src/main/java/io/reactivex/Maybe.java b/src/main/java/io/reactivex/Maybe.java
index ab221724eb..9fd5f6c810 100644
--- a/src/main/java/io/reactivex/Maybe.java
+++ b/src/main/java/io/reactivex/Maybe.java
@@ -2533,7 +2533,7 @@ public final Single<Long> count() {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Maybe<T> defaultIfEmpty(T defaultItem) {
-        ObjectHelper.requireNonNull(defaultItem, "item is null");
+        ObjectHelper.requireNonNull(defaultItem, "defaultItem is null");
         return switchIfEmpty(just(defaultItem));
     }
 
@@ -2709,7 +2709,7 @@ public final Maybe<T> delaySubscription(long delay, TimeUnit unit, Scheduler sch
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Maybe<T> doAfterSuccess(Consumer<? super T> onAfterSuccess) {
-        ObjectHelper.requireNonNull(onAfterSuccess, "doAfterSuccess is null");
+        ObjectHelper.requireNonNull(onAfterSuccess, "onAfterSuccess is null");
         return RxJavaPlugins.onAssembly(new MaybeDoAfterSuccess<T>(this, onAfterSuccess));
     }
 
@@ -2937,7 +2937,7 @@ public final Maybe<T> doOnTerminate(final Action onTerminate) {
     public final Maybe<T> doOnSuccess(Consumer<? super T> onSuccess) {
         return RxJavaPlugins.onAssembly(new MaybePeek<T>(this,
                 Functions.emptyConsumer(), // onSubscribe
-                ObjectHelper.requireNonNull(onSuccess, "onSubscribe is null"),
+                ObjectHelper.requireNonNull(onSuccess, "onSuccess is null"),
                 Functions.emptyConsumer(), // onError
                 Functions.EMPTY_ACTION,    // onComplete
                 Functions.EMPTY_ACTION,    // (onSuccess | onError | onComplete)
@@ -3452,7 +3452,7 @@ public final Single<Boolean> isEmpty() {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Maybe<R> lift(final MaybeOperator<? extends R, ? super T> lift) {
-        ObjectHelper.requireNonNull(lift, "onLift is null");
+        ObjectHelper.requireNonNull(lift, "lift is null");
         return RxJavaPlugins.onAssembly(new MaybeLift<T, R>(this, lift));
     }
 
@@ -4512,7 +4512,7 @@ public final Maybe<T> timeout(long timeout, TimeUnit timeUnit) {
     @NonNull
     @SchedulerSupport(SchedulerSupport.COMPUTATION)
     public final Maybe<T> timeout(long timeout, TimeUnit timeUnit, MaybeSource<? extends T> fallback) {
-        ObjectHelper.requireNonNull(fallback, "other is null");
+        ObjectHelper.requireNonNull(fallback, "fallback is null");
         return timeout(timeout, timeUnit, Schedulers.computation(), fallback);
     }
 
diff --git a/src/main/java/io/reactivex/Observable.java b/src/main/java/io/reactivex/Observable.java
index fe2989bae4..148f96c87b 100644
--- a/src/main/java/io/reactivex/Observable.java
+++ b/src/main/java/io/reactivex/Observable.java
@@ -1738,7 +1738,7 @@ public static <T> Observable<T> error(Callable<? extends Throwable> errorSupplie
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> error(final Throwable exception) {
-        ObjectHelper.requireNonNull(exception, "e is null");
+        ObjectHelper.requireNonNull(exception, "exception is null");
         return error(Functions.justCallable(exception));
     }
 
@@ -2046,7 +2046,7 @@ public static <T> Observable<T> fromPublisher(Publisher<? extends T> publisher)
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> generate(final Consumer<Emitter<T>> generator) {
-        ObjectHelper.requireNonNull(generator, "generator  is null");
+        ObjectHelper.requireNonNull(generator, "generator is null");
         return generate(Functions.<Object>nullSupplier(),
         ObservableInternalHelper.simpleGenerator(generator), Functions.<Object>emptyConsumer());
     }
@@ -2078,7 +2078,7 @@ public static <T> Observable<T> generate(final Consumer<Emitter<T>> generator) {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T, S> Observable<T> generate(Callable<S> initialState, final BiConsumer<S, Emitter<T>> generator) {
-        ObjectHelper.requireNonNull(generator, "generator  is null");
+        ObjectHelper.requireNonNull(generator, "generator is null");
         return generate(initialState, ObservableInternalHelper.simpleBiGenerator(generator), Functions.emptyConsumer());
     }
 
@@ -2114,7 +2114,7 @@ public static <T, S> Observable<T> generate(
             final Callable<S> initialState,
             final BiConsumer<S, Emitter<T>> generator,
             Consumer<? super S> disposeState) {
-        ObjectHelper.requireNonNull(generator, "generator  is null");
+        ObjectHelper.requireNonNull(generator, "generator is null");
         return generate(initialState, ObservableInternalHelper.simpleBiGenerator(generator), disposeState);
     }
 
@@ -2180,7 +2180,7 @@ public static <T, S> Observable<T> generate(Callable<S> initialState, BiFunction
     public static <T, S> Observable<T> generate(Callable<S> initialState, BiFunction<S, Emitter<T>, S> generator,
             Consumer<? super S> disposeState) {
         ObjectHelper.requireNonNull(initialState, "initialState is null");
-        ObjectHelper.requireNonNull(generator, "generator  is null");
+        ObjectHelper.requireNonNull(generator, "generator is null");
         ObjectHelper.requireNonNull(disposeState, "disposeState is null");
         return RxJavaPlugins.onAssembly(new ObservableGenerate<T, S>(initialState, generator, disposeState));
     }
@@ -2386,7 +2386,7 @@ public static Observable<Long> intervalRange(long start, long count, long initia
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item) {
-        ObjectHelper.requireNonNull(item, "The item is null");
+        ObjectHelper.requireNonNull(item, "item is null");
         return RxJavaPlugins.onAssembly(new ObservableJust<T>(item));
     }
 
@@ -2413,8 +2413,8 @@ public static <T> Observable<T> just(T item) {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
 
         return fromArray(item1, item2);
     }
@@ -2444,9 +2444,9 @@ public static <T> Observable<T> just(T item1, T item2) {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
 
         return fromArray(item1, item2, item3);
     }
@@ -2478,10 +2478,10 @@ public static <T> Observable<T> just(T item1, T item2, T item3) {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
 
         return fromArray(item1, item2, item3, item4);
     }
@@ -2515,11 +2515,11 @@ public static <T> Observable<T> just(T item1, T item2, T item3, T item4) {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
 
         return fromArray(item1, item2, item3, item4, item5);
     }
@@ -2555,12 +2555,12 @@ public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5, T item6) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6);
     }
@@ -2598,13 +2598,13 @@ public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7);
     }
@@ -2644,14 +2644,14 @@ public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
-        ObjectHelper.requireNonNull(item8, "The eighth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
+        ObjectHelper.requireNonNull(item8, "item8 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7, item8);
     }
@@ -2693,15 +2693,15 @@ public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8, T item9) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
-        ObjectHelper.requireNonNull(item8, "The eighth item is null");
-        ObjectHelper.requireNonNull(item9, "The ninth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
+        ObjectHelper.requireNonNull(item8, "item8 is null");
+        ObjectHelper.requireNonNull(item9, "item9 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7, item8, item9);
     }
@@ -2745,16 +2745,16 @@ public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> just(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8, T item9, T item10) {
-        ObjectHelper.requireNonNull(item1, "The first item is null");
-        ObjectHelper.requireNonNull(item2, "The second item is null");
-        ObjectHelper.requireNonNull(item3, "The third item is null");
-        ObjectHelper.requireNonNull(item4, "The fourth item is null");
-        ObjectHelper.requireNonNull(item5, "The fifth item is null");
-        ObjectHelper.requireNonNull(item6, "The sixth item is null");
-        ObjectHelper.requireNonNull(item7, "The seventh item is null");
-        ObjectHelper.requireNonNull(item8, "The eighth item is null");
-        ObjectHelper.requireNonNull(item9, "The ninth item is null");
-        ObjectHelper.requireNonNull(item10, "The tenth item is null");
+        ObjectHelper.requireNonNull(item1, "item1 is null");
+        ObjectHelper.requireNonNull(item2, "item2 is null");
+        ObjectHelper.requireNonNull(item3, "item3 is null");
+        ObjectHelper.requireNonNull(item4, "item4 is null");
+        ObjectHelper.requireNonNull(item5, "item5 is null");
+        ObjectHelper.requireNonNull(item6, "item6 is null");
+        ObjectHelper.requireNonNull(item7, "item7 is null");
+        ObjectHelper.requireNonNull(item8, "item8 is null");
+        ObjectHelper.requireNonNull(item9, "item9 is null");
+        ObjectHelper.requireNonNull(item10, "item10 is null");
 
         return fromArray(item1, item2, item3, item4, item5, item6, item7, item8, item9, item10);
     }
@@ -3995,7 +3995,6 @@ public static Observable<Long> timer(long delay, TimeUnit unit, Scheduler schedu
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Observable<T> unsafeCreate(ObservableSource<T> onSubscribe) {
-        ObjectHelper.requireNonNull(onSubscribe, "source is null");
         ObjectHelper.requireNonNull(onSubscribe, "onSubscribe is null");
         if (onSubscribe instanceof Observable) {
             throw new IllegalArgumentException("unsafeCreate(Observable) should be upgraded");
@@ -8157,7 +8156,7 @@ private Observable<T> doOnEach(Consumer<? super T> onNext, Consumer<? super Thro
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Observable<T> doOnEach(final Consumer<? super Notification<T>> onNotification) {
-        ObjectHelper.requireNonNull(onNotification, "consumer is null");
+        ObjectHelper.requireNonNull(onNotification, "onNotification is null");
         return doOnEach(
                 Functions.notificationOnNext(onNotification),
                 Functions.notificationOnError(onNotification),
@@ -9754,7 +9753,7 @@ public final Single<T> lastOrError() {
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Observable<R> lift(ObservableOperator<? extends R, ? super T> lifter) {
-        ObjectHelper.requireNonNull(lifter, "onLift is null");
+        ObjectHelper.requireNonNull(lifter, "lifter is null");
         return RxJavaPlugins.onAssembly(new ObservableLift<R, T>(this, lifter));
     }
 
@@ -11240,7 +11239,7 @@ public final Observable<T> retryWhen(
      */
     @SchedulerSupport(SchedulerSupport.NONE)
     public final void safeSubscribe(Observer<? super T> observer) {
-        ObjectHelper.requireNonNull(observer, "s is null");
+        ObjectHelper.requireNonNull(observer, "observer is null");
         if (observer instanceof SafeObserver) {
             subscribe(observer);
         } else {
@@ -11499,7 +11498,7 @@ public final Observable<T> scan(BiFunction<T, T, T> accumulator) {
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Observable<R> scan(final R initialValue, BiFunction<R, ? super T, R> accumulator) {
-        ObjectHelper.requireNonNull(initialValue, "seed is null");
+        ObjectHelper.requireNonNull(initialValue, "initialValue is null");
         return scanWith(Functions.justCallable(initialValue), accumulator);
     }
 
@@ -13122,7 +13121,7 @@ public final <U> Observable<T> takeUntil(ObservableSource<U> other) {
     @CheckReturnValue
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Observable<T> takeUntil(Predicate<? super T> stopPredicate) {
-        ObjectHelper.requireNonNull(stopPredicate, "predicate is null");
+        ObjectHelper.requireNonNull(stopPredicate, "stopPredicate is null");
         return RxJavaPlugins.onAssembly(new ObservableTakeUntilPredicate<T>(this, stopPredicate));
     }
 
diff --git a/src/main/java/io/reactivex/Single.java b/src/main/java/io/reactivex/Single.java
index d4b5f7aaf4..f7d02b7a99 100644
--- a/src/main/java/io/reactivex/Single.java
+++ b/src/main/java/io/reactivex/Single.java
@@ -584,7 +584,7 @@ public static <T> Single<T> error(final Callable<? extends Throwable> errorSuppl
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public static <T> Single<T> error(final Throwable exception) {
-        ObjectHelper.requireNonNull(exception, "error is null");
+        ObjectHelper.requireNonNull(exception, "exception is null");
         return error(Functions.justCallable(exception));
     }
 
@@ -834,7 +834,7 @@ public static <T> Single<T> fromObservable(ObservableSource<? extends T> observa
     @SchedulerSupport(SchedulerSupport.NONE)
     @NonNull
     public static <T> Single<T> just(final T item) {
-        ObjectHelper.requireNonNull(item, "value is null");
+        ObjectHelper.requireNonNull(item, "item is null");
         return RxJavaPlugins.onAssembly(new SingleJust<T>(item));
     }
 
@@ -2413,7 +2413,7 @@ public final <R> Maybe<R> dematerialize(Function<? super T, Notification<R>> sel
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Single<T> doAfterSuccess(Consumer<? super T> onAfterSuccess) {
-        ObjectHelper.requireNonNull(onAfterSuccess, "doAfterSuccess is null");
+        ObjectHelper.requireNonNull(onAfterSuccess, "onAfterSuccess is null");
         return RxJavaPlugins.onAssembly(new SingleDoAfterSuccess<T>(this, onAfterSuccess));
     }
 
@@ -2980,7 +2980,7 @@ public final T blockingGet() {
     @NonNull
     @SchedulerSupport(SchedulerSupport.NONE)
     public final <R> Single<R> lift(final SingleOperator<? extends R, ? super T> lift) {
-        ObjectHelper.requireNonNull(lift, "onLift is null");
+        ObjectHelper.requireNonNull(lift, "lift is null");
         return RxJavaPlugins.onAssembly(new SingleLift<T, R>(this, lift));
     }
 
@@ -3593,7 +3593,7 @@ public final Disposable subscribe(final Consumer<? super T> onSuccess, final Con
     @SchedulerSupport(SchedulerSupport.NONE)
     @Override
     public final void subscribe(SingleObserver<? super T> observer) {
-        ObjectHelper.requireNonNull(observer, "subscriber is null");
+        ObjectHelper.requireNonNull(observer, "observer is null");
 
         observer = RxJavaPlugins.onSubscribe(this, observer);