Java 11 - Nest Based Access Control

Java 11 introduced a concept of nested class where we can declare a class within a class. This nesting of classes allows to logically group the classes to be used in one place, making them more readable and maintainable. Nested class can be of four types −

• Static nested classes

• Non-static nested classes

• Local classes

• Anonymous classes

Java 11 also provide the concept of nestmate to allow communication and verification of nested classes.

Consider the following example −

ApiTester.java

 import java.util.Arrays; import java.util.Set; import java.util.stream.Collectors; public class APITester { public static void main(String[] args) { boolean isNestMate = APITester.class.isNestmateOf(APITester.Inner.class); boolean nestHost = APITester.Inner.class.getNestHost() == APITester.class; System.out.println(isNestMate); System.out.println(nestHost); Set<String> nestedMembers = Arrays.stream(APITester.Inner.class.getNestMembers()) .map(Class::getName) .collect(Collectors.toSet()); System.out.println(nestedMembers); } public class Inner{} } 

Output

 true true [APITester$Inner, APITester]