Writing a Custom Annotation

Writing a Custom AnnotationWriting a custom annotation is a great way to make your Java code easy to reuse and extend in your own projects. Custom annotations enable you to specify the behavior of a method by supplying parameters to the method's getter and setter methods. This is commonly used in the Java source code to provide dynamic data that can be accessed from a component within your Java application. It is also used in validation and type inference.To write a custom annotation, you use the @NonNull annotation in Java. This means that if the non-nullable annotation on a method is present, the method is presumed to have a null reference. The return value of the method is assumed to be the value returned by the method in case the non-nullable annotation is absent. This declaration tells the compiler to check the return value of the method for null references.To write a custom annotation for use with Java, you will need a source code example. Then you must identify the annotations you are going to annotate. The annotations can be placed inside the method bodies or they can be placed between the method name and the method parameter list.You may have already decided on using annotations for describing types but you may find it useful to annotate both types and instances. In this case, you must specify both the types and the instances are annotated by separating the annotation using a comma. Do not forget to indicate the right names for the types and the instances. If you do not follow this convention, the classes and interfaces will be identified by their package instead of their class names.When you are using multiple types and multiple instances of the same type, you must make sure that the type does not contain a null reference. Java provides several ways to make this determination for you. One way is to check the Javadoc for the type. Another way is to use the equals method of the type to check for nulls.In the java.lang.Object type, you can use the instan ce method to check if an object is of the same type as the object that is being specified. If an object of the same type is found, the custom annotation must be checked for a null reference. For a custom annotation that checks if a method has been overridden, use the super keyword in the custom annotation. This is because the overridable type might be implemented by two different types.To write a custom annotation for the class java.lang.Object, you must use the static modifier to indicate that the check is performed statically. Also, you should use the equals method to specify which type is being compared. The boolean must be either true or false. You may be wondering what would happen if you do not specify a type when using the equals method. The fact is that the boolean should always be one of those two values.To write a custom annotation for instance of the class java.lang.Object, you must use the static modifier to indicate that the check is performed statically. You can use th e instance method to test whether the object is of the same type as the object that is being specified. In either case, the boolean must be one of those two values.