With the release of Java 9, the language has ten new words called restricted keywords. A restricted keyword has a specific meaning in the language, but only if you use that word in a specific way. For example, if you write
requires other.stuff;
you tell Java that your program won't run unless it has access to some other code (the code contained in other.stuff). But if you write
int requires = 10;
then requires is an ordinary int variable.
The following table lists Java's restricted keywords.
| Restricted Keyword | What It Does |
exports |
Indicates that the code in a particular package is available for use by code in other modules. |
module |
A bunch of packages. |
open |
Indicates that all the packages in a module are, in a certain way, available for use by code in other modules. |
opens |
Gets access to all the code in another module. This access uses Java reflection (which tends to be messy). |
provides |
Indicates that a module makes a service available. |
requires |
Indicates that the program won't run unless it has access to the some other code. |
to |
Names the code that has permission to use a particular piece of code. |
transitive |
When my code requires use of the A code, and the Z code requires use of my code, the word transitive means that Z code automatically requires A code. |
uses |
Indicates that a module uses a service. |
with |
Specifies a particular way of using a service. |
