Add sequenceEqual to RxScala

Author: zsxwing

language-adaptors/rxjava-scala/src/examples/scala/rx/lang/scala/examples/RxScalaDemo.scala

@@ -790,4 +790,13 @@ class RxScalaDemo extends JUnitSuite {
     assertEquals(List(1, 2, 3, 4), o.toBlockingObservable.toList)
   }
 
+  @Test def sequenceEqualExampe(): Unit = {
+    val o1 = List(1, 2, 3).toObservable
+    val o2 = List(1, 2, 3).toObservable
+    val o3 = List(1, 2).toObservable
+    val o4 = List(1.0, 2.0, 3.0).toObservable
+    assertTrue(o1.sequenceEqual(o2).toBlockingObservable.single)
+    assertFalse(o1.sequenceEqual(o3).toBlockingObservable.single)
+    assertTrue(o1.sequenceEqual(o4).toBlockingObservable.single)
+  }
 }

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/Observable.scala

@@ -2746,6 +2746,38 @@ trait Observable[+T]
     toScalaObservable[util.Map[K, V]](o).map(m => mapFactory() ++ m.toMap)
   }
 
+  /**
+   * Returns an Observable that emits a Boolean value that indicates whether `this` and `that` Observable sequences are the
+   * same by comparing the items emitted by each Observable pairwise.
+   * <p>
+   * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/sequenceEqual.png">
+   *
+   * Note: this method uses `==` to compare elements. It's a bit different from RxJava which uses `Object.equals`.
+   *
+   * @param that the Observable to compare
+   * @return an Observable that emits a `Boolean` value that indicates whether the two sequences are the same
+   */
+  def sequenceEqual[U >: T](that: Observable[U]): Observable[Boolean] = {
+    sequenceEqual(that, (_1: U, _2: U) => _1 == _2)
+  }
+
+  /**
+   * Returns an Observable that emits a Boolean value that indicates whether `this` and `that` Observable sequences are the
+   * same by comparing the items emitted by each Observable pairwise based on the results of a specified `equality` function.
+   * <p>
+   * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/sequenceEqual.png">
+   *
+   * @param that the Observable to compare
+   * @param equality a function used to compare items emitted by each Observable
+   * @return an Observable that emits a `Boolean` value that indicates whether the two sequences are the same based on the `equality` function.
+   */
+  def sequenceEqual[U >: T](that: Observable[U], equality: (U, U) => Boolean): Observable[Boolean] = {
+    val thisJava: rx.Observable[_ <: U] = this.asJavaObservable
+    val thatJava: rx.Observable[_ <: U] = that.asJavaObservable
+    val equalityJava: Func2[_ >: U, _ >: U, java.lang.Boolean] = equality
+    toScalaObservable[java.lang.Boolean](rx.Observable.sequenceEqual[U](thisJava, thatJava, equalityJava)).map(_.booleanValue)
+  }
+
   /**
    * Lift a function to the current Observable and return a new Observable that when subscribed to will pass
    * the values of the current Observable through the function.