Annotate function interfaces.

src/main/java/io/reactivex/annotations/NonNull.java

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) 2016-present, RxJava Contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is
+ * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
+ * the License for the specific language governing permissions and limitations under the License.
+ */
+
+package io.reactivex.annotations;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.CLASS;
+
+@Documented
+@Target(value = {FIELD, METHOD, PARAMETER, LOCAL_VARIABLE})
+@Retention(value = CLASS)
+public @interface NonNull { }
+

src/main/java/io/reactivex/functions/BiConsumer.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that accepts two values (of possibly different types).
  * @param <T1> the first value type
@@ -26,5 +28,5 @@ public interface BiConsumer<T1, T2> {
      * @param t2 the second value
      * @throws Exception on error
      */
-    void accept(T1 t1, T2 t2) throws Exception;
+    void accept(@NonNull T1 t1, @NonNull T2 t2) throws Exception;
 }

src/main/java/io/reactivex/functions/BiFunction.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -28,5 +30,6 @@ public interface BiFunction<T1, T2, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2) throws Exception;
 }

src/main/java/io/reactivex/functions/BiPredicate.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that returns true or false for the given input values.
  * @param <T1> the first value
@@ -27,5 +29,5 @@ public interface BiPredicate<T1, T2> {
      * @return the boolean result
      * @throws Exception on error
      */
-    boolean test(T1 t1, T2 t2) throws Exception;
+    boolean test(@NonNull T1 t1, @NonNull T2 t2) throws Exception;
 }

src/main/java/io/reactivex/functions/Consumer.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that accepts a single value.
  * @param <T> the value type
@@ -23,5 +25,5 @@ public interface Consumer<T> {
      * @param t the value
      * @throws Exception on error
      */
-    void accept(T t) throws Exception;
+    void accept(@NonNull T t) throws Exception;
 }

src/main/java/io/reactivex/functions/Function.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface that takes a value and returns another value, possibly with a
  * different type and allows throwing a checked exception.
@@ -27,5 +29,6 @@ public interface Function<T, R> {
      * @return the output value
      * @throws Exception on error
      */
-    R apply(T t) throws Exception;
+    @NonNull
+    R apply(@NonNull T t) throws Exception;
 }

src/main/java/io/reactivex/functions/Function3.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -29,5 +31,6 @@ public interface Function3<T1, T2, T3, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2, T3 t3) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2, @NonNull T3 t3) throws Exception;
 }

src/main/java/io/reactivex/functions/Function4.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -31,5 +33,6 @@ public interface Function4<T1, T2, T3, T4, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2, T3 t3, T4 t4) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2, @NonNull T3 t3, @NonNull T4 t4) throws Exception;
 }

src/main/java/io/reactivex/functions/Function5.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -33,5 +35,6 @@ public interface Function5<T1, T2, T3, T4, T5, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2, T3 t3, T4 t4, T5 t5) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2, @NonNull T3 t3, @NonNull T4 t4, @NonNull T5 t5) throws Exception;
 }

src/main/java/io/reactivex/functions/Function6.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -35,5 +37,6 @@ public interface Function6<T1, T2, T3, T4, T5, T6, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2, T3 t3, T4 t4, T5 t5, T6 t6) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2, @NonNull T3 t3, @NonNull T4 t4, @NonNull T5 t5, @NonNull T6 t6) throws Exception;
 }

src/main/java/io/reactivex/functions/Function8.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -39,5 +41,6 @@ public interface Function8<T1, T2, T3, T4, T5, T6, T7, T8, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2, T3 t3, T4 t4, T5 t5, T6 t6, T7 t7, T8 t8) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2, @NonNull T3 t3, @NonNull T4 t4, @NonNull T5 t5, @NonNull T6 t6, @NonNull T7 t7, @NonNull T8 t8) throws Exception;
 }

src/main/java/io/reactivex/functions/Function9.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that computes a value based on multiple input values.
  * @param <T1> the first value type
@@ -41,5 +43,6 @@ public interface Function9<T1, T2, T3, T4, T5, T6, T7, T8, T9, R> {
      * @return the result value
      * @throws Exception on error
      */
-    R apply(T1 t1, T2 t2, T3 t3, T4 t4, T5 t5, T6 t6, T7 t7, T8 t8, T9 t9) throws Exception;
+    @NonNull
+    R apply(@NonNull T1 t1, @NonNull T2 t2, @NonNull T3 t3, @NonNull T4 t4, @NonNull T5 t5, @NonNull T6 t6, @NonNull T7 t7, @NonNull T8 t8, @NonNull T9 t9) throws Exception;
 }

src/main/java/io/reactivex/functions/IntFunction.java

@@ -12,6 +12,8 @@
  */
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that takes a primitive value and return value of type T.
  * @param <T> the returned value type
@@ -23,5 +25,6 @@ public interface IntFunction<T> {
      * @return the result Object
      * @throws Exception on error
      */
+    @NonNull
     T apply(int i) throws Exception;
 }

src/main/java/io/reactivex/functions/Predicate.java

@@ -13,6 +13,8 @@
 
 package io.reactivex.functions;
 
+import io.reactivex.annotations.NonNull;
+
 /**
  * A functional interface (callback) that returns true or false for the given input value.
  * @param <T> the first value
@@ -24,5 +26,5 @@ public interface Predicate<T> {
      * @return the boolean result
      * @throws Exception on error
      */
-    boolean test(T t) throws Exception;
+    boolean test(@NonNull T t) throws Exception;
 }