java注解

1.为什么学习注解:在java框架中注解很多

上图中String [] value():String [] 表示参数类型  value则是参数类型；

package java.lang;

import java.lang.annotation.*;

/**
 * Indicates that a method declaration is intended to override a
 * method declaration in a supertype. If a method is annotated with
 * this annotation type compilers are required to generate an error
 * message unless at least one of the following conditions hold:
 *
 * The method does override or implement a method declared in a
 * supertype.
 * </li><li>
 * The method has a signature that is override-equivalent to that of
 * any public method declared in {@linkplain Object}.

 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.SOURCE)
public @interface Override {
}

2.元注解：注解注解的注解