java8 新增的@Repeatable注解

* java8 新增的@Repeatable注解，其实只是语法糖而已．
 * java8 注解的 {@link RepeatAnn} 类与 {@link Annotations}是等价的．
 * 新注解讲语法糖转化为注解值为数组形式．

package com.github.jdk8.ebook.java8_recipes2nd_edition;import java.lang.annotation.Annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Repeatable;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;import java.util.Arrays;/** * java8 新增的@Repeatable注解，其实只是语法糖而已． * java8 注解的 {@link RepeatAnn} 类与 {@link Annotations}是等价的． * 新注解讲语法糖转化为注解值为数组形式． * @author doctor * * @since 2015年2月3日 下午8:33:43 */public class Chapter2Code {	public static void main(String[] args) {		Annotation[] annotations = RepeatAnn.class.getAnnotations();		System.out.println(annotations.length); //1		Arrays.stream(annotations).forEach(System.out::println);//@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Roles(value=[@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=doctor), @com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=who)])		Annotation[] annotations2 = Annotations.class.getAnnotations();		System.out.println(annotations2.length);//1		Arrays.stream(annotations2).forEach(System.out::println);//@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Roles(value=[@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=doctor), @com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=who)])			}	/**	 * The same annotation can be applied to a declaration or type more than	 * once, given that each annotation is marked as @Repeatable. In the	 * following code, the @Repeatable annotation is used to develop an	 * annotation that can be repeated, rather than grouped together as in	 * previous releases of Java. In this situation, an annotation named Role is	 * being created, and it will be used to signify a role for an annotated	 * class or method.	 * 	 * @author doctor	 *	 * @since 2015年2月3日 下午8:51:09	 */	@Repeatable(value = Roles.class)	public static @interface Role {		String name() default "doctor";	}	@Target(ElementType.TYPE)	@Retention(RetentionPolicy.RUNTIME)	public static @interface Roles {		Role[] value();	}		@Role(name = "doctor")	@Role(name = "who")	public static class RepeatAnn{			}		@Roles({@Role(name="doctor"),			@Role(name="who")})	public static class Annotations{			}}