Java syntax
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Private methods were added in the Java 9 release. An interface can have a method with a body marked as private, in which case it will not be visible to inheriting classes. It can be called from default methods for the purposes of code reuse.
interface Logger {
default void logError() {
log(Level.ERROR);
}
default void logInfo() {
log(Level.INFO);
}
private void log(Level level) {
SystemLogger.log(level.id);
}
}
Annotations
Annotation types
Java has a set of predefined annotation types, but it is allowed to define new ones. An annotation type declaration is a special type of an interface declaration. They are declared in the same way as the interfaces, except the interface keyword is preceded by the @ sign. All annotations are implicitly extended from java.lang.annotation.Annotation and cannot be extended from anything else.
@interface BlockingOperations {
}
Annotations may have the same declarations in the body as the common interfaces, in addition they are allowed to include enums and annotations. The main difference is that abstract method declarations must not have any parameters or throw any exceptions. Also they may have a default value, which is declared using the default keyword after the method name:
@interface BlockingOperations {
boolean fileSystemOperations();
boolean networkOperations() default false;
}
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