Predefined Annotation Types

Java Tutorials - Herong's Tutorial Examples

∟Predefined Annotation Types

This section describes annotation types predefined in the current Java version. A tutorial example is also provided on how to use predefined annotation @Deprecated.

In previous tutorials, we have learned how to declare your own annotation types and use them in annotation invocation statements.

Your own annotation types can help you adding information to your Java programs in a more structured way. But need to build your own tools to parse them and process them.

Before build your own annotation processing tool, you may want to look at annotation types predefined in the JDK package and processed by the "javac" compiler and other tools.

Here is a list of annotation types predefined in the current JDK version:

@Target - Used to annotate a new annotation declaration to limit its targeted program construct types.
@Retention - Used to annotate a new annotation declaration to specify how far the new annotation should be retained, in the source code, in the bytecode class, or in the runtime virtual machine.
@Inherited - Used to annotate a new annotation declaration to specify if it should be inherited to subclasses of the targeted class.
@Override - Used to annotate a method declaration to inform the compiler that the targeted method is overriding the same method in a superclass. This helps the compiler to detect override methods becoming overload methods coding mistakes.
@SuppressWarnings - Used to annotate any declaration to inform the compiler to stop generating some compilation warning messages on the targeted declaration.
@Deprecated - Used to annotate any declaration to inform the compiler to generate "deprecation" warning when the targeted declaration is used in any programs.
@SafeVarargs - Used to annotate a method declaration to inform the compiler to stop generating the "unchecked" warning when a variable parameter with a non-reifiable element type is used.
@Repeatable - Used to annotate a new annotation declaration to specify that it can be used repeatedly as an array element in other annotations.
@FunctionalInterface - Used to annotate an interface declaration to specify that it is a functional interface. This helps the compiler to detect declaration mistakes.

Here is a sample program that shows you how to use the predefined annotation, @Deprecated, on a class declaration:

/* Dummy.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
@Deprecated class Dummy {}

Now if you use this "@Deprecated" in another Java program, you will get a compilation warning.

/* DeprecatedDummyTest.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
class DeprecatedDummyTest {

   Dummy dummy = new Dummy();

   public static void main(String[] arg) {
      System.out.println("Hello world!");
   }
}

Compile the above program to see the warning message:

herong> javac Dummy.java

herong> javac DeprecatedDummyTest.java
Note: DeprecatedDummyTest.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

herong> javac -Xlint:deprecation DeprecatedDummyTest.java
DeprecatedDummyTest.java:6: warning: [deprecation] Dummy in unnamed package
   has been deprecated
   Dummy dummy = new Dummy();
   ^
DeprecatedDummyTest.java:6: warning: [deprecation] Dummy in unnamed package
   has been deprecated
   Dummy dummy = new Dummy();
                     ^