接收键盘输入的字符串，用FileWirter类将字符串写入文件，用FileReader类读出文件内容显示在屏幕上

 public class SY63 {
     public static void main(String[] args) throws Exception {
         System.out.print("请输入字符串:");
         Scanner in = new Scanner(System.in);
         String st = in.nextLine();

         FileWriter fw = new FileWriter("d:\\test.txt");
         fw.write(st);
         fw.close();

         FileReader fr = new FileReader("d:\\test.txt");
         char[] bchar= new char[1024];
         int len = 0;
         while((len = fr.read(bchar)) != -1){
             System.out.print(new String(bchar,0,len));
         }
         fr.close();
     }
 }