用RadomAccessFile.readline()方法读取中文出乱码

Question

void update()
{
    textarea.setText("");
    try
{
RandomAccessFile in=new RandomAccessFile("jilu.txt","rw");
    long filepoint=0;
        while(filepoint<in.length())
        {
         //String s=in.readLine();
         String s=new String(in.readLine().getBytes("iso-8859-1"),"GBK");//转GBK
            textarea.append(s+"\n");
         filepoint=in.getFilePointer();
        }
        in.close();
}
catch(Exception e){}
}这是源码，请指教