If that is shorter than this iterable collection, thatElem values are used to pad the result. RDDs can contain any type of Python, Java, or Scala objects. flatMap can be used as a way to add and remove items (modify the number of items) during a map.In other words, it allows you to map many items to many items (by handling each input item separately), rather than always one-to-one.In this sense, it works like the opposite of filter. TraversableOnce U)(implicit evidence 4 : scala. If this iterable collection is shorter than that, thisElem values are used to pad the result. Creates empty RDD with no partition rdd spark. List (1, 2, 3).map (x > x 2) // List (2, 4, 6) but you want to change the structure of the List and - for example - 'explode' each element into another list then flattening them, flatMap is your friend: List (1, 2, 3).flatMap (x > List. This is one of the major differences between flatMap () and map (), where map () transformation always returns the same number of elements as in input. The length of the returned collection is the maximum of the lengths of this iterable collection and that. AttributesĪ new collection of type That containing pairs consisting of corresponding elements of this iterable collection and that. The element to be used to fill up the result if this iterable collection is shorter than that. The element to be used to fill up the result if that is shorter than this iterable collection. The iterable providing the second half of each result pair If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer. Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs. For Steppers marked with, the converters in allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams. Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example. The implicit parameter defines the resulting Stepper type according to the element type of this collection.įor collections of Int, Short, Byte or Char, an is returnedįor collections of Double or Float, a is returnedįor collections of Long a is returnedįor any other element type, an is returned For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements. For instance: scala> List(1, 2, 3) map ( + 1) res29: ListInt List(2. The Stepper enables creating a Java stream to operate on the collection, see . Mapping over lists: map, flatMap and foreach The operation xs map f takes as. flatMap is passed a FlatMapFunction that accepts a string and returns an. This use is closely related to static members in Java.Returns a for the elements of this collection. The Spark Java API exposes all the Spark features available in the Scala. With these functions it is very easy to process the contents of lists and work with the Option object. Most often, you need an object to hold methods and values/variables that shall be available without having to first instantiate an instance of some class. You can’t really talk about scala without going into the details of the Map, flatMap, zip and reduce functions.
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