import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface Info {
    String name();

    String[] author();

    String comment();
}

@Info(name = "class-InfoClass", author = { "sumy",
        "noclyt" }, comment = "Use to holding username")
public class InfoClass {

    @Info(name = "var-name", author = { "sumy" }, comment = "username")
    private String name;

    @Info(name = "<constructor>", author = {}, comment = "constructor")
    public InfoClass(String name) {
        this.name = name;
    }

    @Info(name = "method-getName", author = {
            "noclyt" }, comment = "a method use to getting username")
    public String getName() {
        return name;
    }
}

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Arrays;

public class TestAnnotation {
    public static void main(String[] args) {
        // 获取类的注解信息
        for (Annotation annotation : InfoClass.class.getAnnotations()) {
            System.out.println("class annotation: " + annotation.toString());
        }

        // 获取变量的注解信息
        for (Field field : InfoClass.class.getDeclaredFields()) {
            // 遍历获取所有注解
            for (Annotation anno : field.getDeclaredAnnotations()) {
                System.out.println("field annotation: " + anno.toString());
            }
        }

        // 获取方法的注解信息
        for (Method method : InfoClass.class.getMethods()) {
            if (method.isAnnotationPresent(Info.class)) { // 判断Info注解是否存在于这个方法
                // 获取指定类型的注解
                Info infoanno = method.getAnnotation(Info.class);
                System.out.println("method annoation: " + infoanno.toString());
                System.out.println(
                        "method " + method.getName() + "'s author(s) is/are "
                                + Arrays.toString(infoanno.author()));
            }
        }
    }
}