org.apache.commons.lang3.stream

Class LangCollectors

java.lang.Object

org.apache.commons.lang3.stream.LangCollectors

public final class LangCollectors
extends Object

Implementations of Collector that implement various reduction operations.

This class is called LangCollectors instead of Collectors to avoid clashes with Collectors.

Since:

3.13.0

Method Summary

Modifier and Type	Method and Description
static <T,R,A> R	collect(Collector<? super T,A,R> collector, T... array) Delegates to Stream.collect(Collector) for a Stream on the given array.
static Collector<Object,?,String>	joining() Returns a Collector that concatenates the input elements, separated by the specified delimiter, in encounter order.
static Collector<Object,?,String>	joining(CharSequence delimiter) Returns a Collector that concatenates the input elements, separated by the specified delimiter, in encounter order.
static Collector<Object,?,String>	joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix) Returns a Collector that concatenates the input elements, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.
static Collector<Object,?,String>	joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix, Function<Object,String> toString) Returns a Collector that concatenates the input elements, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

collect

@SafeVarargs
public static <T,R,A> R collect(Collector<? super T,A,R> collector,
                                             T... array)

Delegates to Stream.collect(Collector) for a Stream on the given array.

Type Parameters:

T - The type of the array elements.

R - the type of the result.

A - the intermediate accumulation type of the Collector.

Parameters:

collector - the Collector describing the reduction.

array - The array, assumed to be unmodified during use, a null array treated as an empty array.

Returns:

the result of the reduction

Since:

3.16.0

See Also:

Stream.collect(Collector), Arrays.stream(Object[]), Collectors

joining

public static Collector<Object,?,String> joining()

Returns a Collector that concatenates the input elements, separated by the specified delimiter, in encounter order.

This is a variation of Collectors.joining() that works with any element class, not just CharSequence.

For example:

 Stream.of(Long.valueOf(1), Long.valueOf(2), Long.valueOf(3))
    .collect(LangCollectors.joining())
 returns "123"
 

Returns:

A Collector which concatenates Object elements, separated by the specified delimiter, in encounter order.

joining

public static Collector<Object,?,String> joining(CharSequence delimiter)

Returns a Collector that concatenates the input elements, separated by the specified delimiter, in encounter order.

This is a variation of Collectors.joining(CharSequence) that works with any element class, not just CharSequence.

For example:

 Stream.of(Long.valueOf(1), Long.valueOf(2), Long.valueOf(3))
   .collect(LangCollectors.joining("-"))
 returns "1-2-3"
 

Parameters:

delimiter - the delimiter to be used between each element.

Returns:

A Collector which concatenates Object elements, separated by the specified delimiter, in encounter order.

joining

public static Collector<Object,?,String> joining(CharSequence delimiter,
                                                 CharSequence prefix,
                                                 CharSequence suffix)

Returns a Collector that concatenates the input elements, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.

This is a variation of Collectors.joining(CharSequence, CharSequence, CharSequence) that works with any element class, not just CharSequence.

For example:

 Stream.of(Long.valueOf(1), Long.valueOf(2), Long.valueOf(3))
   .collect(LangCollectors.joining("-", "[", "]"))
 returns "[1-2-3]"
 

Parameters:

delimiter - the delimiter to be used between each element

prefix - the sequence of characters to be used at the beginning of the joined result

suffix - the sequence of characters to be used at the end of the joined result

Returns:

A Collector which concatenates CharSequence elements, separated by the specified delimiter, in encounter order

joining

public static Collector<Object,?,String> joining(CharSequence delimiter,
                                                 CharSequence prefix,
                                                 CharSequence suffix,
                                                 Function<Object,String> toString)

Returns a Collector that concatenates the input elements, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.

This is a variation of Collectors.joining(CharSequence, CharSequence, CharSequence) that works with any element class, not just CharSequence.

For example:

 Stream.of(Long.valueOf(1), null, Long.valueOf(3))
   .collect(LangCollectors.joining("-", "[", "]", o -> Objects.toString(o, "NUL")))
 returns "[1-NUL-3]"
 

Parameters:

delimiter - the delimiter to be used between each element

prefix - the sequence of characters to be used at the beginning of the joined result

suffix - the sequence of characters to be used at the end of the joined result

toString - A function that takes an Object and returns a non-null String.

Returns:

A Collector which concatenates CharSequence elements, separated by the specified delimiter, in encounter order