Java annotations

How to create basic custom annotation

package com.java2novice.annotations;

public interface MySampleAnn

{

    String name();

    String desc();

}

class MyAnnTest

{

    MySampleAnn(name = "test1", desc = "testing annotations")

    public void myTestMethod()

    {

    }

}

What is Retention policy in java annotations

package com.java2novice.annotations;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

Retention(RetentionPolicy.Runtime)

Public interface MySampleAnn

{

   String name();

    String desc();

}

class MyAnnTest

{

    MySampleAnn(name = "test1", desc = "testing annotations")

    public void myTestMethod()

   {

       }

}

How to get annotations at runtime using java reflection

package com.java2novice.annotations;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.reflect.Method;

Retention(RetentionPolicy.Runtime)

interface MyAnnotation

{

    String key();

    String value();

}

public class MyAnnotationTest

{

   MyAnnotation(key="site", value="java2novice.com")

    public void myAnnotationTestMethod()

{

         try

       {

            Class MyAnnotationTest> cls = this.getClass();

            Method mth = cls.getMethod("myAnnotationTestMethod");

            MyAnnotation myAnno = mth.getAnnotation(MyAnnotation.class);

            System.out.println("key: "+myAnno.key());

            System.out.println("value: "+myAnno.value());

         }

         catch (SecurityException e)

         {

         e.printStackTrace();

        }

        catch (NoSuchMethodException e)

        {

            e.printStackTrace();

        }

    }

    public static void main(String a[])

   {

        MyAnnotationTest mat = new MyAnnotationTest();

        mat.myAnnotationTestMethod();

    }

}

 How to get all annotations from a class

package com.java2novice.annotations;

import java.lang.annotation.Annotation;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.reflect.Method;

Retention(RetentionPolicy.Runtime)

interface MyAnnoOne

{

    String key();

    String value();

}

Retention(RetentionPolicy.Runtime)

interface MyAnnoTwo

{

     int count();

}

public class MyMultipleAnns

{

      MyAnnoTwo(count=20)

        MyAnnoOne(key="site", value="java2novice.com")

 public void myAnnotationTestMethod()

{

 try

     {

            Class MyMultipleAnns> cls = this.getClass();

            Method mth = cls.getMethod("myAnnotationTestMethod");

            Annotation[] anns = mth.getAnnotations();

            for(Annotation an:anns)

           {

                System.out.println(an);

            }

        }

        catch (SecurityException e)

       {

        e.printStackTrace();

        }

        catch (NoSuchMethodException e)

       {

                   e.printStackTrace();

        }

    }

    public static void main(String a[])

   {

        MyMultipleAnns mat = new MyMultipleAnns();

        mat.myAnnotationTestMethod();

    }

}