Package org.junit.platform.commons.util
Class CollectionUtils
- java.lang.Object
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- org.junit.platform.commons.util.CollectionUtils
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@API(status=INTERNAL, since="1.0") public final class CollectionUtils extends java.lang.Object
Collection of utilities for working withCollections
.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
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static <T> T
getOnlyElement(java.util.Collection<T> collection)
Read the only element of a collection of size 1.static java.util.stream.Stream<?>
toStream(java.lang.Object object)
Convert an object of one of the following supported types into aStream
.static <T> java.util.stream.Collector<T,?,java.util.List<T>>
toUnmodifiableList()
Return aCollector
that accumulates the input elements into a new unmodifiable list, in encounter order.
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Method Detail
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getOnlyElement
public static <T> T getOnlyElement(java.util.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 isnull
or does not contain exactly one element
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toUnmodifiableList
public static <T> java.util.stream.Collector<T,?,java.util.List<T>> toUnmodifiableList()
Return aCollector
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
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toStream
public static java.util.stream.Stream<?> toStream(java.lang.Object object)
Convert an object of one of the following supported types into aStream
.Stream
DoubleStream
IntStream
LongStream
Collection
Iterable
Iterator
Object
array
- Parameters:
object
- the object to convert into a stream; nevernull
- Returns:
- the resulting stream
- Throws:
PreconditionViolationException
- if the supplied object isnull
or not one of the supported types
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