| Utility classes are classes that only include static members and are not |
| designed to be instantiated, for example `java.lang.Math` or `java.util.Arrays`. |
| |
| In the absence of explicit constructors, however, the compiler provides a |
| public, parameterless default constructor. To a user, this constructor is |
| indistinguishable from any other. It is not uncommon for a published API to |
| accidentally include a public constructor for a class intended to be |
| uninstantiable. |
| |
| To prevent users from instantiating classes that are not designed to be |
| instantiated, you can add a private constructor: |
| |
| ```java |
| public class UtilityClass { |
| private UtilityClass() {} |
| } |
| ``` |
| |
| See: |
| |
| * [Effective Java 3rd Edition ยง4][ej3e-4] |
| |
| [ej3e-4]: https://books.google.com/books?id=BIpDDwAAQBAJ |
