Using Custom Annotation¶
Question¶
ADDQUESTION
Solution¶
import java.lang.annotation.*;
import static java.lang.annotation.ElementType.*; // @Target arguments
import static java.lang.annotation.RetentionPolicy.*; // @Retention arguments
import java.lang.reflect.*;
/**
* Example 164 - Declaring and Using a Custom Annotation Type
*/
enum Day {
Mon, Tue, Wed, Thu, Fri, Sat, Sun;
private final static Day[] day = values();
public static Day toDay(int n) { return day[n];}
public int toInt() { return ordinal(); }
}
enum Month {
Jan(31), Feb(28), Mar(31), Apr(30), May(31), Jun(30),
Jul(31), Aug(31), Sep(30), Oct(30), Nov(30), Dec(31);
private final int days;
private Month(int days) {
this.days = days;
}
private final static Month[] month = values();
public int days(int year) {
// Simplistic - Does not take care of Leap year
return days;
}
public static Month toMonth(int n) {
return month[n-1];
}
public int toInt() {
return ordinal()+1;
}
public Month succ() {
return toMonth(toInt() + 1);
}
}
@Target({TYPE, METHOD})
@Retention(RUNTIME)
@interface Author {
public int oneHour = 60 * 60 * 1000;
public String name();
public Month month();
public String[] diet() default {"iddiappam", "chappati"};
public int weeklyWork() default 56 * oneHour;
}
@Retention(RUNTIME)
@interface Authors {
public Author[] value();
}
class UsingCustomAnnotation {
@Author(name="Senthil", month=Month.Jan, diet= {"iddiappam"})
public void myMethod1() {}
@Author(name="Shalini", month=Month.Mar, diet= {"chappati"})
public void myMethod2() {}
public static void main(String[] args) {
Class ty = UsingCustomAnnotation.class;
for (Method mif: ty.getMethods()) {
System.out.println("\nGetting the annotations of " + mif.getName());
// This finds only annotations with RUNTIME retention
Annotation[] annos = mif.getDeclaredAnnotations();
System.out.println("The annotations are: ");
for(Annotation anno: annos)
System.out.println(anno);
}
}
}