一篇文章带你搞定JAVA注解

package org.pdool.anno;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface CheckEnum {
}

package org.pdool.anno;

public enum ResType {
   GoLD(1),
   DIAMOND(2),
   //注意：此处重复
   SILVER(2);
   int type;
   @CheckEnum
   public int getType() {
       return type;
  }
   ResType(int type) {
       this.type = type;
  }
}

package org.pdool.anno;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashSet;
import java.util.Set;

public class Aain {
   public static void main(String[] args) throws InvocationTargetException,IllegalAccessException {
       // 获取有注解的方法
       Method[] declaredMethods = ResType.class.getDeclaredMethods();
       Method annoMethod = null;
       for (Method declaredMethod : declaredMethods) {
           CheckEnum  annotation = declaredMethod.getAnnotation(CheckEnum.class);
           if (annotation != null){
               annoMethod = declaredMethod;
              break;
          }
      }
       Set<Object> set = new HashSet<>();
       // 遍历每个枚举的id
       Object[] oo = ResType.class.getEnumConstants();
       for (Object o : oo) {
           Object invoke = annoMethod.invoke(o);
           if (!set.contains(invoke)){
               set.add(invoke);
          }else {
               System.out.println("重复的key "+ o +" -- "+ invoke);
          }
      }
  }
}