字节流怎么转换成字符流？

下面是字节流转换成字符流的代码
package cn.itcast;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class OutputStreamWriterDemo {
        public static void main(String[] args) throws IOException {
                OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("a.txt"), "GBK");
                char[] chs={'我','叫'};
                osw.write(chs);
                osw.close();
                InputStreamReader isr=new InputStreamReader(new FileInputStream("a.txt"),"GBK");
                //char ch=0;
                char[] chuf=new char[1024];
                int len=0;
                while((len=isr.read(chuf))!=-1){
                        System.out.print(new String(chuf,0,len));
                }
                isr.close();
        }
}