Lesson 20 - Enumerated types and constants in Java

Java OOP Enumerated types and constants in Java

In the previous lesson, Abstract class, comparing and anonymous classes in Java, we went over abstract classes and learned how to compare instances of custom classes. The last 3 lessons were very practical, as in lots of doing and getting right into sample programs. This time around we're going to get back into theoretical concepts for a little bit.

Enumerated types

A common thing in software development is having a variable that is only supposed to contain one of a set of specific values. An example might be an order status in an e-shop. The order may be new, accepted, approved or completed. It cannot be in any other state in order to function properly. Other examples include the days of the week, job positions and so on. With our current knowledge, we could probably store the order status as a string. Doing so is a common cause of errors since we wouldn't have a mechanism to check whether the value is valid. Therefore, Java provides enumerated types (enums). We declare an enum similarly as a class.

We'll add an enum to a project as we do it with a class or an interface, but


 

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This lesson is about enumerated types (enums) and EnumSets in Java. We'll also learn to use the final keyword and implement class constants.

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Article has been written for you by David Capka
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