1、需求：复制一个文本文件

FileReader fr = new FileReader("a.txt");

FileWriter fw = new FileWriter("b.txt");

BufferedReader bufr = new BufferedReader(fr);

BufferedWriter bufw = new BufferedWriter(fw);

2、需求：读取键盘录入信息，写入到文件中

源：InputStream in = System.in;

转换流：InputStreamReader isr = new InputStreamReader(in);

目的：FileWriter fw = new FileWriter("b.txt");

高效：BufferedReader = new BufferedReader(isr);

     BufferedWriter = new BufferedWriter(fw);

3、需求：将一个文本文件显示在控制台上

源：FileReader fr = new FileReader("a.txt");

读： String line = bufr.readLine();

目的：OutputStream out = System.out;

      OutputStreamWriter osw = new OutputStreamWriter(out);

高效：BufferedReader bufr = new BufferedReader(fr);
     BufferedWriter bufw = new BufferedWriter(osw);

4、需求：读取键盘录入数据，显示在控制台上

源：InputStream in = System.in    ;

目的：OutputStream out = System.out;

转换流：InputStreamReader isr = new InputStreamReader(in);
        OutputStreamWriter isw = new OutputStreamWriter(out);

高效：BufferedReader bufr = new BufferedReader(isr);
      BufferedWriter bufw = new BufferedWriter(isw);