Package org.junit.platform.commons.util

Class CollectionUtils

java.lang.Object

org.junit.platform.commons.util.CollectionUtils

@API(status=INTERNAL,
     since="1.0")
public final class CollectionUtils
extends Object

Collection of utilities for working with Collections.

DISCLAIMER

These utilities are intended solely for usage within the JUnit framework itself. Any usage by external parties is not supported. Use at your own risk!

Since:

1.0

Method Summary

Modifier and Type	Method	Description
static <T> T	getOnlyElement(Collection<T> collection)	Read the only element of a collection of size 1.
static Stream<?>	toStream(Object object)	Convert an object of one of the following supported types into a Stream.
static <T> Collector<T,?,List<T>>	toUnmodifiableList()	Return a Collector that accumulates the input elements into a new unmodifiable list, in encounter order.

Methods inherited from class java.lang.Object

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

Method Detail

getOnlyElement

public static <T> T getOnlyElement(Collection<T> collection)

Read the only element of a collection of size 1.

Parameters:

collection - the collection to get the element from

Returns:

the only element of the collection

Throws:

PreconditionViolationException - if the collection is null or does not contain exactly one element

toUnmodifiableList

public static <T> Collector<T,?,List<T>> toUnmodifiableList()

Return a Collector that accumulates the input elements into a new unmodifiable list, in encounter order.

There are no guarantees on the type or serializability of the list returned, so if more control over the returned list is required, consider creating a new Collector implementation like the following:

 public static <T> Collector<T, ?, List<T>> toUnmodifiableList(Supplier<List<T>> listSupplier) {
     return Collectors.collectingAndThen(Collectors.toCollection(listSupplier), Collections::unmodifiableList);
 }
 

Type Parameters:

T - the type of the input elements

Returns:

a Collector which collects all the input elements into an unmodifiable list, in encounter order

toStream

public static Stream<?> toStream(Object object)

Convert an object of one of the following supported types into a Stream.

• Stream
• DoubleStream
• IntStream
• LongStream
• Collection
• Iterable
• Iterator
• Object array
• primitive array

Parameters:

object - the object to convert into a stream; never null

Returns:

the resulting stream

Throws:

PreconditionViolationException - if the supplied object is null or not one of the supported types