RKTechGame | Java Annotations Explained

Java Annotations kya hoti hain?

Annotations ek tarah ke metadata hote hain jo Java code me additional information provide karte hain. Yeh program ke behavior ko directly change nahi karte, lekin compiler ya runtime tools ko information dete hain.

Annotations ke Types

• Marker Annotations: Data nahi rakhte, sirf presence ka indication dete hain. Jaise @Override
• Single-value Annotations: Sirf ek value rakhte hain. Jaise @SuppressWarnings("unchecked")
• Full Annotations: Multiple values ke pairs rakhte hain. Jaise @Author(name="John", date="2025-08-26")
• Type Annotations: Java 8 se types ke upar bhi apply kiye ja sakte hain. Jaise @NonNull String name;
• Repeating Annotations: Ek hi annotation ko multiple baar apply karne ke liye.

Custom Annotation Kaise Banaye

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    String value();
    String author() default "RKTechGame";
}

Yeh custom annotation MyAnnotation hai jisme ek mandatory value aur ek optional author element hai.

Custom Annotation Apply Karna

@MyAnnotation(value = "This class is annotated", author = "User")
public class MyClass {
    // Class content yahan
}

Is example me MyClass class ko humne MyAnnotation se annotate kiya hai.

Common Predefined Annotations

• @Override: Method override karne ke liye.
• @Deprecated: Purana code indicate karta hai jo future me hata bhi sakte hain.
• @SuppressWarnings: Compiler warnings ko suppress karne ke liye.
• @FunctionalInterface: Functional interface mark karne ke liye.