• aggregate( ) — see reduce( )
• all( ) — determine whether all items emitted by an Observable meet some criteria
• amb( ) — given two or more source Observables, emits all of the items from the first of these Observables to emit an item
• ambWith( ) — instance version of amb( )
• and( ) — combine the emissions from two or more source Observables into a Pattern (rxjava-joins)
• apply( ) (scala) — see create( )
• asObservable( ) (kotlin) — see from( ) (et al.)
• asyncAction( ) — convert an Action into an Observable that executes the Action and emits its return value (rxjava-async)
• asyncFunc( ) — convert a function into an Observable that executes the function and emits its return value (rxjava-async)
• averageDouble( ) — calculates the average of Doubles emitted by an Observable and emits this average (rxjava-math)
• averageFloat( ) — calculates the average of Floats emitted by an Observable and emits this average (rxjava-math)
• averageInteger( ) — calculates the average of Integers emitted by an Observable and emits this average (rxjava-math)
• averageLong( ) — calculates the average of Longs emitted by an Observable and emits this average (rxjava-math)
• blocking( ) (clojure) — see toBlocking( )
• buffer( ) — periodically gather items from an Observable into bundles and emit these bundles rather than emitting the items one at a time
• byLine( ) (StringObservable) — converts an Observable of Strings into an Observable of Lines by treating the source sequence as a stream and splitting it on line-endings
• cache( ) — remember the sequence of items emitted by the Observable and emit the same sequence to future Subscribers
• cast( ) — cast all items from the source Observable into a particular type before reemitting them
• catch( ) (clojure) — see onErrorResumeNext( )
• chunkify( ) — returns an iterable that periodically returns a list of items emitted by the source Observable since the last list (⁇)
• collect( ) — collects items emitted by the source Observable into a single mutable data structure and returns an Observable that emits this structure
• combineLatest( ) — when an item is emitted by either of two Observables, combine the latest item emitted by each Observable via a specified function and emit items based on the results of this function
• combineLatestWith( ) (scala) — instance version of combineLatest( )
• concat( ) — concatenate two or more Observables sequentially
• concatMap( ) — transform the items emitted by an Observable into Observables, then flatten this into a single Observable, without interleaving
• concatWith( ) — instance version of concat( )
• connect( ) — instructs a Connectable Observable to begin emitting items
• cons( ) (clojure) — see concat( )
• contains( ) — determine whether an Observable emits a particular item or not
• count( ) — counts the number of items emitted by an Observable and emits this count
• countLong( ) — counts the number of items emitted by an Observable and emits this count
• create( ) — create an Observable from scratch by means of a function
• cycle( ) (clojure) — see repeat( )
• debounce( ) — only emit an item from the source Observable after a particular timespan has passed without the Observable emitting any other items
• decode( ) (StringObservable) — convert a stream of multibyte characters into an Observable that emits byte arrays that respect character boundaries
• defaultIfEmpty( ) — emit items from the source Observable, or emit a default item if the source Observable completes after emitting no items
• defer( ) — do not create the Observable until a Subscriber subscribes; create a fresh Observable on each subscription
• deferFuture( ) — convert a Future that returns an Observable into an Observable, but do not attempt to get the Observable that the Future returns until a Subscriber subscribes (rxjava-async)
• deferCancellableFuture( ) — convert a Future that returns an Observable into an Observable in a way that monitors the subscription status of the Observable to determine whether to halt work on the Future, but do not attempt to get the returned Observable until a Subscriber subscribes (⁇)(rxjava-async)
• delay( ) — shift the emissions from an Observable forward in time by a specified amount
• dematerialize( ) — convert a materialized Observable back into its non-materialized form
• distinct( ) — suppress duplicate items emitted by the source Observable
• distinctUntilChanged( ) — suppress duplicate consecutive items emitted by the source Observable
• do( ) (clojure) — see doOnEach( )
• doOnCompleted( ) — register an action to take when an Observable completes successfully
• doOnEach( ) — register an action to take whenever an Observable emits an item
• doOnError( ) — register an action to take when an Observable completes with an error
• doOnNext( ) — see doOnEach( )
• doOnRequest( ) — register an action to take when items are requested from an Observable via reactive-pull backpressure (⁇)
• doOnSubscribe( ) — register an action to take when an observer subscribes to an Observable
• doOnTerminate( ) — register an action to take when an Observable completes, either successfully or with an error
• doOnUnsubscribe( ) — register an action to take when an observer unsubscribes from an Observable
• doWhile( ) — emit the source Observable's sequence, and then repeat the sequence as long as a condition remains true (contrib-computation-expressions)
• drop( ) (scala/clojure) — see skip( )
• dropRight( ) (scala) — see skipLast( )
• dropUntil( ) (scala) — see skipUntil( )
• dropWhile( ) (scala) — see skipWhile( )
• drop-while( ) (clojure) — see skipWhile( )
• elementAt( ) — emit item n emitted by the source Observable
• elementAtOrDefault( ) — emit item n emitted by the source Observable, or a default item if the source Observable emits fewer than n items
• empty( ) — create an Observable that emits nothing and then completes
• encode( ) (StringObservable) — transform an Observable that emits strings into an Observable that emits byte arrays that respect character boundaries of multibyte characters in the original strings
• error( ) — create an Observable that emits nothing and then signals an error
• every( ) (clojure) — see all( )
• exists( ) — determine whether an Observable emits any items or not
• filter( ) — filter items emitted by an Observable
• finally( ) (clojure) — see finallyDo( )
• filterNot( ) (scala) — see filter( )
• finallyDo( ) — register an action to take when an Observable completes
• first( ) (Observable) — emit only the first item emitted by an Observable, or the first item that meets some condition
• first( ) (BlockingObservable) — emit only the first item emitted by an Observable, or the first item that meets some condition
• firstOrDefault( ) (Observable) — emit only the first item emitted by an Observable, or the first item that meets some condition, or a default value if the source Observable is empty
• firstOrDefault( ) (BlockingObservable) — emit only the first item emitted by an Observable, or the first item that meets some condition, or a default value if the source Observable is empty
• firstOrElse( ) (scala) — see firstOrDefault( ) or firstOrDefault( ) (BlockingObservable)
• flatMap( ) — transform the items emitted by an Observable into Observables, then flatten this into a single Observable
• flatMapIterable( ) — create Iterables corresponding to each emission from a source Observable and merge the results into a single Observable
• flatMapIterableWith( ) (scala) — instance version of flatMapIterable( )
• flatMapWith( ) (scala) — instance version of flatmap( )
• flatten( ) (scala) — see merge( )
• flattenDelayError( ) (scala) — see mergeDelayError( )
• foldLeft( ) (scala) — see reduce( )
• forall( ) (scala) — see all( )
• forEach( ) (Observable) — see subscribe( )
• forEach( ) (BlockingObservable) — invoke a function on each item emitted by the Observable; block until the Observable completes
• forEachFuture( ) (Async) — pass Subscriber methods to an Observable but also have it behave like a Future that blocks until it completes (rxjava-async)
• forEachFuture( ) (BlockingObservable)— create a futureTask that will invoke a specified function on each item emitted by an Observable (⁇)
• forIterable( ) — apply a function to the elements of an Iterable to create Observables which are then concatenated (⁇)
• from( ) — convert an Iterable, a Future, or an Array into an Observable
• from( ) (StringObservable) — convert a stream of characters or a Reader into an Observable that emits byte arrays or Strings
• fromAction( ) — convert an Action into an Observable that invokes the action and emits its result when a Subscriber subscribes (rxjava-async)
• fromCallable( ) — convert a Callable into an Observable that invokes the callable and emits its result or exception when a Subscriber subscribes (rxjava-async)
• fromCancellableFuture( ) — convert a Future into an Observable in a way that monitors the subscription status of the Observable to determine whether to halt work on the Future, but do not attempt to get the Future's value until a Subscriber subscribes (⁇)(rxjava-async)
• fromFunc0( ) — see fromCallable( ) (rxjava-async)
• fromFuture( ) — convert a Future into an Observable, but do not attempt to get the Future's value until a Subscriber subscribes (⁇)
• fromRunnable( ) — convert a Runnable into an Observable that invokes the runable and emits its result when a Subscriber subscribes (rxjava-async)
• generate( ) — create an Observable that emits a sequence of items as generated by a function of your choosing (⁇)
• generateAbsoluteTime( ) — create an Observable that emits a sequence of items as generated by a function of your choosing, with each item emitted at an item-specific time (⁇)
• generator( ) (clojure) — see generate( )
• getIterator( ) — convert the sequence emitted by the Observable into an Iterator
• groupBy( ) — divide an Observable into a set of Observables that emit groups of items from the original Observable, organized by key
• group-by( ) (clojure) — see groupBy( )
• groupByUntil( ) — a variant of the groupBy( ) operator that closes any open GroupedObservable upon a signal from another Observable (⁇)
• groupJoin( ) — combine the items emitted by two Observables whenever one item from one Observable falls within a window of duration specified by an item emitted by the other Observable
• head( ) (scala) — see first( ) (BlockingObservable)
• headOption( ) (scala) — see firstOrDefault( ) or firstOrDefault( ) (BlockingObservable)
• headOrElse( ) (scala) — see firstOrDefault( ) or firstOrDefault( ) (BlockingObservable)
• ifThen( ) — only emit the source Observable's sequence if a condition is true, otherwise emit an empty or default sequence (contrib-computation-expressions)
• ignoreElements( ) — discard the items emitted by the source Observable and only pass through the error or completed notification
• interval( ) — create an Observable that emits a sequence of integers spaced by a given time interval
• into( ) (clojure) — see reduce( )
• isEmpty( ) — determine whether an Observable emits any items or not
• items( ) (scala) — see just( )
• join( ) — combine the items emitted by two Observables whenever one item from one Observable falls within a window of duration specified by an item emitted by the other Observable
• join( ) (StringObservable) — converts an Observable that emits a sequence of strings into an Observable that emits a single string that concatenates them all, separating them by a specified string
• just( ) — convert an object into an Observable that emits that object
• last( ) (BlockingObservable) — block until the Observable completes, then return the last item emitted by the Observable
• last( ) (Observable) — emit only the last item emitted by the source Observable
• lastOption( ) (scala) — see lastOrDefault( ) or lastOrDefault( ) (BlockingObservable)
• lastOrDefault( ) (BlockingObservable) — block until the Observable completes, then return the last item emitted by the Observable or a default item if there is no last item
• lastOrDefault( ) (Observable) — emit only the last item emitted by an Observable, or a default value if the source Observable is empty
• lastOrElse( ) (scala) — see lastOrDefault( ) or lastOrDefault( ) (BlockingObservable)
• latest( ) — returns an iterable that blocks until or unless the Observable emits an item that has not been returned by the iterable, then returns the latest such item
• length( ) (scala) — see count( )
• limit( ) — see take( )
• longCount( ) (scala) — see countLong( )
• map( ) — transform the items emitted by an Observable by applying a function to each of them
• mapcat( ) (clojure) — see concatMap( )
• mapMany( ) — see: flatMap( )
• materialize( ) — convert an Observable into a list of Notifications
• max( ) — emits the maximum value emitted by a source Observable (rxjava-math)
• maxBy( ) — emits the item emitted by the source Observable that has the maximum key value (rxjava-math)
• merge( ) — combine multiple Observables into one
• mergeDelayError( ) — combine multiple Observables into one, allowing error-free Observables to continue before propagating errors
• merge-delay-error( ) (clojure) — see mergeDelayError( )
• mergeMap( ) * — see: flatMap( )
• mergeMapIterable( ) — see: flatMapIterable( )
• mergeWith( ) — instance version of merge( )
• min( ) — emits the minimum value emitted by a source Observable (rxjava-math)
• minBy( ) — emits the item emitted by the source Observable that has the minimum key value (rxjava-math)
• mostRecent( ) — returns an iterable that always returns the item most recently emitted by the Observable
• multicast( ) — represents an Observable as a Connectable Observable
• never( ) — create an Observable that emits nothing at all
• next( ) — returns an iterable that blocks until the Observable emits another item, then returns that item
• nonEmpty( ) (scala) — see isEmpty( )
• nth( ) (clojure) — see elementAt( ) and elementAtOrDefault( )
• observeOn( ) — specify on which Scheduler a Subscriber should observe the Observable
• ofType( ) — emit only those items from the source Observable that are of a particular class
• onBackpressureBlock( ) — block the Observable's thread until the Observer is ready to accept more items from the Observable (⁇)
• onBackpressureBuffer( ) — maintain a buffer of all emissions from the source Observable and emit them to downstream Subscribers according to the requests they generate
• onBackpressureDrop( ) — drop emissions from the source Observable unless there is a pending request from a downstream Subscriber, in which case emit enough items to fulfill the request
• onErrorFlatMap( ) — instructs an Observable to emit a sequence of items whenever it encounters an error (⁇)
• onErrorResumeNext( ) — instructs an Observable to emit a sequence of items if it encounters an error
• onErrorReturn( ) — instructs an Observable to emit a particular item when it encounters an error
• onExceptionResumeNext( ) — instructs an Observable to continue emitting items after it encounters an exception (but not another variety of throwable)
• orElse( ) (scala) — see defaultIfEmpty( )
• parallel( ) — split the work done on the emissions from an Observable into multiple Observables each operating on its own parallel thread (⁇)
• parallelMerge( ) — combine multiple Observables into smaller number of Observables (⁇)
• pivot( ) — combine multiple sets of grouped observables so that they are arranged primarily by group rather than by set (⁇)
• publish( ) — represents an Observable as a Connectable Observable
• publishLast( ) — represent an Observable as a Connectable Observable that emits only the last item emitted by the source Observable (⁇)
• range( ) — create an Observable that emits a range of sequential integers
• reduce( ) — apply a function to each emitted item, sequentially, and emit only the final accumulated value
• reductions( ) (clojure) — see scan( )
• refCount( ) — makes a Connectable Observable behave like an ordinary Observable
• repeat( ) — create an Observable that emits a particular item or sequence of items repeatedly
• repeatWhen( ) — create an Observable that emits a particular item or sequence of items repeatedly, depending on the emissions of a second Observable
• replay( ) — ensures that all Subscribers see the same sequence of emitted items, even if they subscribe after the Observable begins emitting the items
• rest( ) (clojure) — see next( )
• return( ) (clojure) — see just( )
• retry( ) — if a source Observable emits an error, resubscribe to it in the hopes that it will complete without error
• retrywhen( ) — if a source Observable emits an error, pass that error to another Observable to determine whether to resubscribe to the source
• runAsync( ) — returns a StoppableObservable that emits multiple actions as generated by a specified Action on a Scheduler (rxjava-async)
• sample( ) — emit the most recent items emitted by an Observable within periodic time intervals
• scan( ) — apply a function to each item emitted by an Observable, sequentially, and emit each successive value
• seq( ) (clojure) — see getIterator( )
• sequenceEqual( ) — test the equality of sequences emitted by two Observables
• sequenceEqualWith( ) (scala) — instance version of sequenceEqual( )
• serialize( ) — force an Observable to make serialized calls and to be well-behaved
• share( ) — see refCount( )
• single( ) (BlockingObservable) — if the source Observable completes after emitting a single item, return that item, otherwise throw an exception
• single( ) (Observable) — if the source Observable completes after emitting a single item, emit that item, otherwise notify of an exception
• singleOption( ) (scala) — see singleOrDefault( ) (BlockingObservable)
• singleOrDefault( ) (BlockingObservable) — if the source Observable completes after emitting a single item, return that item, otherwise return a default item
• singleOrDefault( ) (Observable) — if the source Observable completes after emitting a single item, emit that item, otherwise emit a default item
• singleOrElse( ) (scala) — see singleOrDefault( )
• size( ) (scala) — see count( )
• skip( ) — ignore the first n items emitted by an Observable
• skipLast( ) — ignore the last n items emitted by an Observable
• skipUntil( ) — discard items emitted by a source Observable until a second Observable emits an item, then emit the remainder of the source Observable's items
• skipWhile( ) — discard items emitted by an Observable until a specified condition is false, then emit the remainder
• sliding( ) (scala) — see window( )
• slidingBuffer( ) (scala) — see buffer( )
• split( ) (StringObservable) — converts an Observable of Strings into an Observable of Strings that treats the source sequence as a stream and splits it on a specified regex boundary
• start( ) — create an Observable that emits the return value of a function (rxjava-async)
• startCancellableFuture( ) — convert a function that returns Future into an Observable that emits that Future's return value in a way that monitors the subscription status of the Observable to determine whether to halt work on the Future (⁇)(rxjava-async)
• startFuture( ) — convert a function that returns Future into an Observable that emits that Future's return value (rxjava-async)
• startWith( ) — emit a specified sequence of items before beginning to emit the items from the Observable
• stringConcat( ) (StringObservable) — converts an Observable that emits a sequence of strings into an Observable that emits a single string that concatenates them all
• subscribeOn( ) — specify which Scheduler an Observable should use when its subscription is invoked
• sumDouble( ) — adds the Doubles emitted by an Observable and emits this sum (rxjava-math)
• sumFloat( ) — adds the Floats emitted by an Observable and emits this sum (rxjava-math)
• sumInt( ) — adds the Integers emitted by an Observable and emits this sum (rxjava-math)
• sumLong( ) — adds the Longs emitted by an Observable and emits this sum (rxjava-math)
• switch( ) (scala) — see switchOnNext( )
• switchCase( ) — emit the sequence from a particular Observable based on the results of an evaluation (contrib-computation-expressions)
• switchMap( ) — transform the items emitted by an Observable into Observables, and mirror those items emitted by the most-recently transformed Observable
• switchOnNext( ) — convert an Observable that emits Observables into a single Observable that emits the items emitted by the most-recently emitted of those Observables
• synchronize( ) — see serialize( )
• take( ) — emit only the first n items emitted by an Observable
• takeFirst( ) — emit only the first item emitted by an Observable, or the first item that meets some condition
• takeLast( ) — only emit the last n items emitted by an Observable
• takeLastBuffer( ) — emit the last n items emitted by an Observable, as a single list item
• takeRight( ) (scala) — see last( ) (Observable) or takeLast( )
• takeUntil( ) — emits the items from the source Observable until a second Observable emits an item
• takeWhile( ) — emit items emitted by an Observable as long as a specified condition is true, then skip the remainder
• take-while( ) (clojure) — see takeWhile( )
• then( ) — transform a series of Pattern objects via a Plan template (rxjava-joins)
• throttleFirst( ) — emit the first items emitted by an Observable within periodic time intervals
• throttleLast( ) — emit the most recent items emitted by an Observable within periodic time intervals
• throttleWithTimeout( ) — only emit an item from the source Observable after a particular timespan has passed without the Observable emitting any other items
• throw( ) (clojure) — see error( )
• timeInterval( ) — emit the time lapsed between consecutive emissions of a source Observable
• timeout( ) — emit items from a source Observable, but issue an exception if no item is emitted in a specified timespan
• timer( ) — create an Observable that emits a single item after a given delay
• timestamp( ) — attach a timestamp to every item emitted by an Observable
• toAsync( ) — convert a function or Action into an Observable that executes the function and emits its return value (rxjava-async)
• toBlocking( ) — transform an Observable into a BlockingObservable
• toBlockingObservable( ) - see toBlocking( )
• toFuture( ) — convert the Observable into a Future
• toIterable( ) — convert the sequence emitted by the Observable into an Iterable
• toIterator( ) — see getIterator( )
• toList( ) — collect all items from an Observable and emit them as a single List
• toMap( ) — convert the sequence of items emitted by an Observable into a map keyed by a specified key function
• toMultimap( ) — convert the sequence of items emitted by an Observable into an ArrayList that is also a map keyed by a specified key function
• toSeq( ) (scala) — see toList( )
• toSortedList( ) — collect all items from an Observable and emit them as a single, sorted List
• tumbling( ) (scala) — see window( )
• tumblingBuffer( ) (scala) — see buffer( )
• using( ) — create a disposable resource that has the same lifespan as an Observable
• when( ) — convert a series of Plan objects into an Observable (rxjava-joins)
• where( ) — see: filter( )
• whileDo( ) — if a condition is true, emit the source Observable's sequence and then repeat the sequence as long as the condition remains true (contrib-computation-expressions)
• window( ) — periodically subdivide items from an Observable into Observable windows and emit these windows rather than emitting the items one at a time
• zip( ) — combine sets of items emitted by two or more Observables together via a specified function and emit items based on the results of this function
• zipWith( ) — instance version of zip( )
• zipWithIndex( ) (scala) — see zip( )
• ++ (scala) — see concat( )
• +: (scala) — see startWith( )

(⁇) — this proposed operator is not part of RxJava 1.0