实现：从控制台读取要复制的源文件名和目标文件名，将源文件中的内容复制到目标文件中

 1 public class CopyFile {
 2     private static BufferedReader stdIn =
 3                                     new BufferedReader(
 4                                         new InputStreamReader(System.in))'
 5     private static PrintWriter stdOut =
 6                                     new PrintWriter(System.out, true);//标准结果
 7     private static PrintWriter stdErr = 
 8                                     new PrintWriter(System.err, true);//提示信息或者错误信息
 9 
10     public static void main(String[] args) throws IOException {
11         stdErr.print("Source filename:    ");
12         stdErr.flush();//保证将上述提示信息显示在屏幕上
13 
14         BufferedReader input =  new BufferedReader(
15                                     new FileReader(stdIn.readLine()));//读用户输入的内容
16         stdErr.print("Destination filename：    ")；
17         stdErr.flush();
18         
19         PrintWriter output = 
20                 new PrintWriter(new FileWriter(stdIn.readLine()));
21         String line = input.readLine();
22 
23         while (line!=null) {
24             output.println(line);
25             line = input.readLine();
26         }
27         
28         input.close();
29         output.close();
30 
31         stdOut.println("done");
32 }