echo.java

Java程序设计技巧与开发实例附书源代码。

import java.io.*;

public class Echo
{
   public static void main(String args[])
   {
      PrintStream out = null;
      if (args.length == 1)
      {
         String fileName = args[0];
         try
         {
            out = new PrintStream(new FileOutputStream(fileName));
            System.out.println("Output redirected to " + fileName);
            System.setOut(out);
         }
         catch (IOException ioe)
         {
            System.err.println(ioe);
         }
      }
      else
      {
         System.out.println("Output not redirected to a file");
      }
      System.err.println("Enter the single word 'quit' to quit");
      String s = new String();
      while (!s.equals("quit"))
      {
         s = Console.readString();
         System.out.println(s);
      }
      if (out != null)
      {
         out.close();
      }
   }
}