Target annotation in java example

Spike 38 Published: 09/18/2024

Target annotation in java example

Here is a Java example of target annotation:

import java.lang.annotation.*;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Loggable {
String message() default "Method executed";
}

In this code, we are creating an annotation called Loggable which can be applied to a method.

The @Target annotation specifies the type of Java element that this annotation can be used on. In this case, it is METHOD, so only methods can have this annotation.

The @Retention annotation specifies how long this annotation should be retained. We are specifying that this annotation should be kept until runtime (RUNTIME).

Inside the Loggable interface, we are declaring a single method called message. This method returns a string and has a default value of "Method executed". This means that when an annotation is not specified for a method, it will automatically have this message as its value.

Here is how you can use this annotation in your code:

public class Example {
@Loggable("This is my own log message")
public void myMethod() {
System.out.println("Hello");
}
}

In the above example, we are applying the @Loggable annotation to our myMethod. If you print out the message of this annotated method using a reflection-based logging framework (for instance), it would say "This is my own log message".

What is target in Java?

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In Java programming, the term "target" can have different meanings depending on the context. Here are some possible interpretations:

Java Virtual Machine (JVM) Target: When compiling Java code, the target refers to the specific JVM architecture that the generated bytecode is intended for. For example, you might specify a target like "1.8" or "11" to indicate compatibility with the corresponding version of the JVM.

Android Target: In Android app development using Java, the target specifies the minimum API level required by your application. This setting determines which devices can run your app, as it restricts the available features and hardware configurations. For instance, if you set the target to "28" (the level for Android 9.0), your app will only be compatible with devices running that or higher version. Java Target Compatibility: Another sense of "target" is related to compatibility between different Java versions. In this context, a target can refer to the minimum or maximum version of Java that an application or library is designed to work with. For example, you might specify that your project targets Java 14 or later. Code Generation Target: When using a Java compiler, the target can influence how the code is generated. For instance, you might set the target to generate bytecode for a specific JVM version or architecture (e.g., "armeabi-v7a" for ARM-based devices). Testing and Debugging Target: In software testing and debugging, the target refers to the specific platform, environment, or configuration that the tests are intended to run on. For example, you might create separate test targets for different device types (e.g., "emulator" for Android emulator testing) or operating systems.

In summary, the term "target" in Java can have various meanings depending on the context, ranging from JVM architecture and API level specifications to code generation, platform selection, and testing configurations.