Lesson 9 - The Collections Java utility class - Creating collections
In the previous lesson, The Collections Java utility class - Getting and modifying, we learned how to use the
Collections Java utility class for getting and modifying collection
data. In today's Java tutorial, we're going to complete this survey by
introducing the functionality for creating new collections.
Creating new collections
The class has plenty of methods for creating empty collections of various
types. Usually it's about implementing a certain interface, but with zero number
of elements. Maybe you ask, what are these methods for? Such methods are useful,
for example, when we need to return a collection of elements matching some
condition. If no item satisfies the condition, we simply return an empty
collection, for example, using the Collections.emptyList() method.
It's much better than returning null, and clearer than returning
Optional<List<T>>.
All the empty*() methods return an
unmodifiable collection. This means that you're not able to add,
remove, or get any element from that collection.
Wrappers
Methods that belong to this category create wrappers over existing collections. The wrappers are of three types:
- synchronization wrappers
- unmodifiable wrappers
- typesafe wrappers
Synchronization wrappers
Synchronization wrappers are used to
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In this Java tutorial, we'll discuss the Collections utility class in detail, this time the synchronization, unmodifiable and typesafe wrappers.
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