java字符串写入文件

import java.io.*;
class ReaderTest
{
    public static void main(String [] args)throws Exception
    {
    FileOutputStream fos=new FileOutputStream("a.txt");
    OutputStreamWriter osw=new OutputStreamWriter(fos);
    BufferedWriter bw=new BufferedWriter(osw);
    bw.write("写入文件");
    bw.close();

    FileInputStream fis=new FileInputStream("a.txt");
    InputStreamReader isr=new InputStreamReader(fis);
    BufferedReader br=new BufferedReader(isr);
    System.out.println(br.readLine());
    br.close();
    }
}