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JAVA EXAMPLE PROGRAMS

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How to assign default values to custom annotations?


Description:

  • We can assign default values to annotation members. These values will be return incase if you didn't provide any values to the annotation members.
  • We can assign default values by using default clause during members declarations. Make sure that the default values are same type as members.
  • Below example shows how to assign default vlaues to annotation members.


Code:
package com.java2novice.annotations;

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


@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnot{
	
	String key() default "site";
	String value() default "java2novice.com";
}

public class MyAnnotDefaultValues {

	@MyAnnot()
	public void myAnnotationTestMethod(){
		
		try {
			Class<? extends MyAnnotDefaultValues> cls = this.getClass();
			Method mth = cls.getMethod("myAnnotationTestMethod");
			MyAnnot myAnno = mth.getAnnotation(MyAnnot.class);
			System.out.println("key: "+myAnno.key());
			System.out.println("value: "+myAnno.value());
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main(String a[]){
		
		MyAnnotDefaultValues mat = new MyAnnotDefaultValues();
		mat.myAnnotationTestMethod();
	}
}

Output:
key: site
value: java2novice.com
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Knowledge Centre
What is transient variable?
Transient variables cannot be serialized. During serialization process, transient variable states will not be serialized. State of the value will be always defaulted after deserialization.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected] or you can comment on the page.

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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