added combineLatest static methods to Observable

Author: jmhofer

rxjava-core/src/main/java/rx/Observable.java

@@ -40,6 +40,7 @@
 import rx.observables.GroupedObservable;
 import rx.operators.OperationAll;
 import rx.operators.OperationCache;
+import rx.operators.OperationCombineLatest;
 import rx.operators.OperationConcat;
 import rx.operators.OperationDefer;
 import rx.operators.OperationDematerialize;
@@ -2737,6 +2738,35 @@ public R call(T0 t0, T1 t1, T2 t2, T3 t3) {
         });
     }
 
+    /**
+     * Combines the given observables, emitting an event containing an aggregation of the latest values of each of the source observables
+     * each time an event is received from one of the source observables, where the aggregation is defined by the given function.
+     * @param w0 
+     *          The first source observable.
+     * @param w1 
+     *          The second source observable.
+     * @param combineLatestFunction 
+     *          The aggregation function used to combine the source observable values.
+     * @return A function from an observer to a subscription. This can be used to create an observable from.
+     */
+    public static <R, T0, T1> Observable<R> combineLatest(Observable<T0> w0, Observable<T1> w1, Func2<T0, T1, R> combineFunction) {
+        return create(OperationCombineLatest.combineLatest(w0, w1, combineFunction));
+    }
+    
+    /**
+     * @see #combineLatest(Observable, Observable, Func2)
+     */
+    public static <R, T0, T1, T2> Observable<R> combineLatest(Observable<T0> w0, Observable<T1> w1, Observable<T2> w2, Func3<T0, T1, T2, R> combineFunction) {
+        return create(OperationCombineLatest.combineLatest(w0, w1, w2, combineFunction));
+    }
+
+    /**
+     * @see #combineLatest(Observable, Observable, Func2)
+     */
+    public static <R, T0, T1, T2, T3> Observable<R> combineLatest(Observable<T0> w0, Observable<T1> w1, Observable<T2> w2, Observable<T3> w3, Func4<T0, T1, T2, T3, R> combineFunction) {
+        return create(OperationCombineLatest.combineLatest(w0, w1, w2, w3, combineFunction));
+    }
+    
     /**
      * Filters an Observable by discarding any of its emissions that do not meet some test.
      * <p>