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


 

...End of the preview...

Premium article

Premium article

ict.social is a large database made up of manuals and tutorials, whose main goal is to provide high-quality IT education to everyone. We started out in the Czech republic, where we display roughly a million articles per month and receive plenty of gratitude from our users. Thanks to our successful establishment, we are now bringing these articles to the rest of the world.

Although we are trying to keep our content free of charge, maintaining the site is a huge effort for everyone involved. Therefore, some content (exercises and more advanced material) costs network points. Don't worry, they're really cheap :)

Article description

Requested article covers this content:

In this Java tutorial, we'll discuss the Collections utility class in detail, this time the synchronization, unmodifiable and typesafe wrappers.

Limited offer: Learn all knowledge and save money

Buy articles and tests separately one by one 80 points
Buy the course including all articles and features for an exclusive price 68 points
Currently, you have 0 points
By buying this exclusive package, you'll have access to all 13 articles in this course including exercise submitting while saving $1.08. This offer is limited for the first articles only with an additional exclusive 15% discount.
You gain 68 points for adding an article to the site, or for $7.20 $6.12

Buy just this article

Warning, by buying just this article you'll lose the limited 15% discount for the package of all the articles.

To access the article, you need 10 points
Currently, you have 0 points
You gain 10 points for adding an article to the site, or for $0.90

Buying this article gives you unlimited access to it forever. You will learn some more and help us keep giving our site maintenance which helps you and others get better futures. It's a win-win.

This article is licensed :Premium, by buying this article, you agree with the terms of use.

You gain points by supporting our network. This is done by sending a helpful amount of money to support the site, or by creating content for the network.

You can get points immediately using:

Credit card SMS Wire transfer
Credit card SMS Wire transfer

 

Activities (2)