一个简单的jna小程序，运行过程中，在new Structure的那一步会报错，麻烦各位高手给看看

[joywings]

一个简单的小程序，想尝试使用jna的Structure，我是Java初学者，还请各位大大给看看怎么搞定啊

package com;
import com.sun.jna.*;

public class wp_demo
{		
	public static class AAA extends Structure{
		public static class ByReference extends AAA implements Structure.ByReference {}
		int a;
		int b;
	}

	public static void main(String[] args)
	{
		AAA etherDevice = new AAA();
		//
	}
}

运行会报下面的错误：

Exception in thread "main" java.lang.IllegalArgumentException: Structure class com.wp_demo$AAA has unknown size (ensure all fields are public)
at com.sun.jna.Structure.calculateSize(Structure.java:1013)
at com.sun.jna.Structure.allocateMemory(Structure.java:247)
at com.sun.jna.Structure.<init>(Structure.java:150)
at com.sun.jna.Structure.<init>(Structure.java:140)
at com.sun.jna.Structure.<init>(Structure.java:136)
at com.sun.jna.Structure.<init>(Structure.java:127)
at com.wp_demo$AAA.<init>(wp_demo.java:6)
at com.wp_demo.main(wp_demo.java:14)

[joywings]

额，找到问题了

    public static class AAA extends Structure{
        public static class ByReference extends AAA implements Structure.ByReference {}
        int a;
        int b;
    }

改成

	public static class AAA extends Structure{
		public static class ByReference extends AAA implements Structure.ByReference{}
		public int a;
		public int b;
	}