IO流，带缓冲区的字符流。

public static void main(String[] args) throws IOException{

　　BufferedReader br = new BufferedReader (new FileReader("xxx.txt"));

　　BufferedWriter bw = new BufferedWriter (new FileWriter("yyy.txt"));

　　int c;

　　while((c = br.read()) != -1){

　　　　bw.write(c);

　　}

　　br.close();

　　bw.close();

}