org.apache.tapestry5.func

Interface Flow<T>

All Superinterfaces:

FlowOperations<T,Flow<T>>, Iterable<T>

public interface Flow<T>
extends FlowOperations<T,Flow<T>>

A flow is a a functional interface for working with an ordered collection of elements. A given Flow contains only elements of a particular type. Standard operations allow for filtering the flow, or appending elements to the Flow. Since flows are immutable, all operations on flows return new immutable flows. Flows are thread safe (to the extent that the Mapper , Predicate , Worker and Reducer objects applied to the flow are). Flows are lazy: filtering, mapping, and concatenating flows will do so with no, or a minimum, of evaluation. However, converting a Flow into a List (or other collection) will force a realization of the entire flow. In some cases, a flow may be an infinite, lazily evaluated sequence. Operations that iterate over all elements (such as FlowOperations.count() or FlowOperations.reduce(Reducer, Object)) may become infinite loops. Using flows allows for a very fluid interface. Flows are initially created using F.flow(java.util.Collection), F.flow(Object...) or F.flow(Iterable).

Since:

5.2.0

See Also:

F.lazy(LazyFunction)

Method Summary

Modifier and Type	Method and Description
<V extends T> Flow<T>	append(V... values) Appends any number of type compatible values to the end of this Flow.
Flow<T>	concat(Flow<? extends T> other) Returns a new Flow with the other Flow's elements appended to this Flow's.
Flow<T>	interleave(Flow<T>... otherFlows) "Stripes" together a group of flows.
<X> Flow<X>	map(Mapper<T,X> mapper) Maps a Flow into a new Flow with different type values.
<X,Y> Flow<Y>	map(Mapper2<T,X,Y> mapper, Flow<? extends X> flow) Combines two Flows using a two-parameter Mapper.
<X> Flow<X>	mapcat(Mapper<T,Flow<X>> mapper) Given a Mapper that maps a T to a Flow<X>, this method will lazily concatenate all the output flows into a single Flow<X>.
Flow<T>	sort() Sorts this Flow, forming a new Flow.
T[]	toArray(Class<T> type) Converts the Flow into an array of values (due to type erasure, you have to remind the Flow about the type).
<X> ZippedFlow<T,X>	zipWith(Flow<X> otherFlow) Zips this Flow together with another flow to form a Flow of Tuples.

Methods inherited from interface org.apache.tapestry5.func.FlowOperations

concat, count, drop, each, filter, first, isEmpty, reduce, remove, removeNulls, rest, reverse, sort, take, toList, toSet

Methods inherited from interface java.lang.Iterable

forEach, iterator, spliterator

Method Detail

map

<X> Flow<X> map(Mapper<T,X> mapper)

Maps a Flow into a new Flow with different type values. Mapping is a lazy operation.

map

<X,Y> Flow<Y> map(Mapper2<T,X,Y> mapper,
                  Flow<? extends X> flow)

Combines two Flows using a two-parameter Mapper. Each element of this Flow, and the corresponding element of the other flow are passed through the Mapper to provide the elements of the output Flow. The length of the result Flow is the smaller of the lengths of the two input Flows. Mapping is a lazy operation.

mapcat

<X> Flow<X> mapcat(Mapper<T,Flow<X>> mapper)

Given a Mapper that maps a T to a Flow<X>, this method will lazily concatenate all the output flows into a single Flow<X>.

toArray

T[] toArray(Class<T> type)

Converts the Flow into an array of values (due to type erasure, you have to remind the Flow about the type).

concat

Flow<T> concat(Flow<? extends T> other)

Returns a new Flow with the other Flow's elements appended to this Flow's. This is a lazy operation.

append

<V extends T> Flow<T> append(V... values)

Appends any number of type compatible values to the end of this Flow. This is a lazy operation.

sort

Flow<T> sort()

Sorts this Flow, forming a new Flow. This is a non-lazy operation; it will fully realize the values of the Flow.

Throws:

ClassCastException - if type T does not extend Comparable

zipWith

<X> ZippedFlow<T,X> zipWith(Flow<X> otherFlow)

Zips this Flow together with another flow to form a Flow of Tuples. The resulting flow is the length of the shorter of the two input flows. Zipping flows together is a lazy operation. The elements of this flow become the Tuple.first value in each Tuple, the elements of the other flow become the Tuple.second value in each Tuple.

Type Parameters:

X - type of element stored in the other flow

Parameters:

otherFlow - contains elements to match with elements in this flow

Returns:

flow of tuples combining values from this flow with values form the other flow

Since:

5.3

interleave

Flow<T> interleave(Flow<T>... otherFlows)

"Stripes" together a group of flows. The output flow contains the first value from this flow, then the first value from each of the other flows, in turn, then the second value from this flow, etc. The resulting flow ends when this or any of the other flows runs out of values.

Returns:

combined flow