Hello, Java developers!
In this session, we’re going to explore Java Annotations, a form of metadata that provides data about a program but is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate.
Built-in Annotations in Java
Java provides several built-in annotations. Some of the most commonly used are:
@Override: Indicates that a method declaration is intended to override a method declaration in a superclass.@Deprecated: Marks the annotated element as obsolete, advising not to use it.@SuppressWarnings: Instructs the compiler to suppress specific warnings that it would otherwise generate.Example of using built-in annotations:
java
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public class MyClass {
@Override
public String toString() {
return "MyClass{}";
}
@Deprecated
public void oldMethod() {
// ...
}
@SuppressWarnings("unchecked")
public void myMethod() {
// ...
}
}
Custom Annotations
You can also create your own annotations in Java.
Example of a custom annotation:
java
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import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyCustomAnnotation {
String value();
}
Using a Custom Annotation:
java
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public class MyClass {
@MyCustomAnnotation(value = "Example of custom annotation")
public void myMethod() {
// ...
}
}
Exercise: Use Annotations in a Java Class
For your exercise, create a Java class and:
Use the @Override annotation for a method that overrides a method from its superclass.Create and apply a custom annotation to a method or class field.Use the @Deprecated annotation to mark a method as deprecated.Conclusion
Congratulations! You’ve just learned about annotations in Java. Annotations are a powerful way to provide metadata about your code, influencing how it should be used, checked, or processed.
Experiment with both built-in and custom annotations in your Java projects to see how they can improve readability, functionality, and maintainability of your code.
Happy coding, and explore the potential of Java annotations!