JAVA的字符编码问题，错误解码，再编码，再正确解码，出来是乱码

示例代码如下：
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package javacharsettest;

import java.io.UnsupportedEncodingException;

/**
*
* @author jiayp
*/
public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        try {
            String str = "a你好b";
            str = new String(str.getBytes("GBK"), "UTF-8");
            str = new String(str.getBytes("UTF-8"), "GBK");

            System.out.print(str);
        }catch(UnsupportedEncodingException e){};

    }
}

请问有办法把错误解码的字符串给还原回去吗？