Question

// Demonstrate a repeated annotation.
import java.lang.annotation.*;
import java.lang.reflect.*;

// Make MyAnno repeatable.
@Retention(RetentionPolicy.RUNTIME)
@Repeatable(MyRepeatedAnnos.class)
@interface MyAnno {
    String str() default "Testing";
    int val() default 9000;
}

// This is the container annotation.
@Retention(RetentionPolicy.RUNTIME)
@interface MyRepeatedAnnos {
    MyAnno[] value();
}

class RepeatAnno {
    // Repeat MyAnno on myMeth().
    @MyAnno(str = "First annotation", val = -1)
    @MyAnno(str = "Second annotation", val = 100)
    public static void myMeth(String str, int i)
    {
        RepeatAnno ob = new RepeatAnno();
        try {
            Class<?> c = ob.getClass();
            // Obtain the annotations for myMeth().
            Method m = c.getMethod("myMeth", String.class, int.class);
            // Display the repeated MyAnno annotations.
            Annotation anno = m.getAnnotation(MyRepeatedAnnos.class);
            System.out.println(anno);
        } catch (NoSuchMethodException exc) {
            System.out.println("Method Not Found.");
        }
    }
    public static void main(String args[]) {
        myMeth("test", 10);
    }
}

我已从一本书中复制粘贴此代码，并尝试使用jdk版本1.8.0_131在我的系统中运行此代码，但我收到以下编译错误：

error: cannot find symbol
@Repeatable(MyRepeatedAnnos.class)
 ^
  symbol: class Repeatable
RepeatAnno.java:19: error: duplicate annotation
@MyAnno(str = "Second annotation", val = 100)
^
2 errors

我无法理解这里有什么问题。请帮忙。

java 8中的可重复注释

0 个答案: