用RandomAccessFile处理中文的问题

用RandomAccessFile处理中文的时候,总是在读到最后的时候出现EOFException,或者出现乱码,请各位帮我看看,多谢下面是源码:
输入是cutoff.txt,内容是"你们可好"
希望运行后cutoff.txt的内容是"可好可好"import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;public class CutOff {
    
    private static String sourceFile = "cutoff.txt";
    
    public static void main(String[] args){
        try {
            RandomAccessFile accessor = new RandomAccessFile(sourceFile,"rw");
            
            long length = accessor.length()/2;
            long readIndex = length;
            long writeIndex = 0;
            byte b;
            char c;
            
            for(;writeIndex<length;){
                accessor.seek(readIndex);
                b = accessor.readByte();
                if(b<0){
                    c = accessor.readChar();
                    accessor.seek(writeIndex);
                    accessor.writeChar(c);
                    readIndex = readIndex + 2;
                    writeIndex = writeIndex + 2;
                }else{
                    accessor.seek(writeIndex);
                    accessor.writeByte(b);
                    readIndex++;
                    writeIndex++;
                }
            }
            accessor.close();
        } catch (FileNotFoundException ex) {
            ex.printStackTrace();
        } catch (IOException ex){
            ex.printStackTrace();
        }
    }
}