java代码不明白，求解读

Question

public static void main(String[] args) {

FileReader fr = null;

FileWriter fw = null;

try {

fr = new FileReader("C:\my.txt");

fw = new FileWriter("D:\you.txt");

        char []buf = new char[1024];  
        int len = 0;  
        //读一个数组大小，写一个数组大小方法。  
        while((len = fr.read(buf)) != -1){  
            fw.write(buf, 0, len);                
        }  

    } catch (Exception e) {  
        System.out.println(e.toString());  
    } finally {  
        if (fr != null)  
            try {  
                fr.close();  
            } catch (Exception e2) {  
                throw new RuntimeException("关闭失败！");  
            }  
        if (fw != null)  
            try {  
                fw.close();  
            } catch (IOException e) {  
                throw new RuntimeException("关闭失败！");  
            }  
    }  
}  

}

其中while((len = fr.read(buf)) != -1){

fw.write(buf, 0, len);

}

这一句不明白，求详细解答

Answer 1

将my.txt读成流写入you.txt