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Annotations in Java

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Last updated: May 25, 2026
Author: ManaCoding Team
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Annotations in Java provide metadata about code. They do not change program logic but give instructions to the compiler or runtime tools (like Spring, Hibernate).

📝 Syntax 
@Override
public String toString() {
  return "Hello";
}
💻 Example Program 
import java.lang.annotation.*;

@interface Info {
  String author();
  int version();
}

@Info(author = "Jai", version = 1)
class Demo {

  @Deprecated
  public void oldMethod() {
    System.out.println("Old method");
  }

  @Override
  public String toString() {
    return "Demo Class";
  }

}

public class Main {

  public static void main(String[] args) {

    Demo d = new Demo();
    d.oldMethod();
    System.out.println(d.toString());

  }

}

// Output:
// Old method
// Demo Class
💡 What are Annotations?
  • 1 Provide metadata about code.
  • 2 Do not change program logic.
  • 3 Used by compiler and frameworks.
  • 4 Part of java.lang package.
💡 Types of Annotations
  • 1 @Override – method override check.
  • 2 @Deprecated – marks old code.
  • 3 @SuppressWarnings – suppress warnings.
  • 4 Custom annotations.
💡 Why Use Annotations?
  • 1 To provide metadata.
  • 2 To improve code readability.
  • 3 To support frameworks.
  • 4 To reduce boilerplate code.
💡 Custom Annotations
  • 1 Defined using @interface.
  • 2 Can have elements (fields).
  • 3 Used with reflection.
  • 4 Processed at compile or runtime.
✅ Quick Summary
  • Annotations provide metadata in Java.
  • They do not affect program logic.
  • Used heavily in frameworks.
  • Can be built-in or custom.
❓ FAQs
What are annotations in Java?
They are metadata that provide information about code.
Do annotations affect program logic?
No, they only provide metadata.
What is @Override used for?
It indicates that a method overrides a superclass method.
Can we create custom annotations?
Yes, using @interface keyword.
Which frameworks use annotations?
Spring, Hibernate, and JUnit.
🎯 Interview Questions
Q1. What are annotations in Java?
Answer: They are metadata that provide information about code.
Q2. Do annotations affect program logic?
Answer: No, they only provide metadata.
Q3. What is @Override used for?
Answer: It indicates that a method overrides a superclass method.
Q4. Can we create custom annotations?
Answer: Yes, using @interface keyword.
Q5. Which frameworks use annotations?
Answer: Spring, Hibernate, and JUnit.
❓ Quiz

What is the purpose of annotations in Java?

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