What's meant by a class name being a plural in Java, such as "Collections"?

java, naming-conventions

Solution

There are several classes in java that are plural despite them not being utilities. These include `DoubleSummaryStatistics` and `IntSummaryStatistics.java`. I think the primary meaning is "Does making this class plural improve the understanding of the class or make it more readable?" `DoubleSummaryStatistic` would likely be non representative of the class itself. The majority of plural classes are utilities or constants. The other, are sometimes extensions of a `HashMap` for properties or attributes. From `java.util`, the following classes are plural:

LongSummaryStatistics.java - public class 
Attributes.java - public class
IntSummaryStatistics.java - public class
Properties.java - public class 
DoubleSummaryStatistics.java - public class

Executors.java - Utility
Helpers.java - Utility
ArrayPrefixHelpers.java - Utility
Spliterators.java - Utility
ZipUtils.java - Utility
Comparators.java - Utility
ArraysParallelSortHelpers.java - Utility
Collections.java - Utility
Collectors.java - Utility
Streams.java - Utility
SortedOps.java - Utility
FindOps.java - Utility
ReduceOps.java - Utility
WhileOps.java - Utility
DistinctOps.java - Utility
StreamSpliterators.java - Utility
ForEachOps.java - Utility
Nodes.java - Utility
SliceOps.java - Utility
MatchOps.java - Utility
Objects.java - Utility
Arrays.java - Utility

FormattableFlags.java - Constants
CharPredicates.java - Constants 
ZipConstants.java - Constants

Problem

I've encountered some class names being plural in Java, such as `Collections` (not to be confused with `Collection`), and Package java.util lists a couple of others in that package alone, such as `Arrays` and `Objects`. In general, what's meant by a class name being plural? Does it always mean that it's a set of utility static methods, like with `Collections`?

Original source