开启一个文本文件，并将该文档内字符以相反次序输出到另一个文档中

/*题目：编写一个Java程序要求：开启一个文本文件， *并将该文档内字符以相反次序输出到另一个文档中 * */package test;import java.io.*;import java.util.Scanner;public class File_1_1{ /**  * @param args  */ public void getFile(String pathreader,String pathwriter) {  try  {   String st;  //字符串临时存储变量   int i = 0;  //统计数组元素个数   FileReader fr = new FileReader(pathreader);   FileWriter fw = new FileWriter(pathwriter);   BufferedReader br = new BufferedReader(fr);   BufferedWriter bw = new BufferedWriter(fw);   //返回文件内容的行数 countline(pathreader)   String str[] = new String[countline(pathreader)];   //利用StringBuffer对象主要是利用该对象中的倒序方法   StringBuffer sub;   StringBuffer data = new StringBuffer(br.readLine());   while(data.toString() != null)   {    sub = new StringBuffer(data.toString().length());    sub = data.reverse();  //将字符串的内容倒序    str[i] = sub.toString(); //   System.out.println(str[i]);    i = i + 1;    if((st = br.readLine()) != null)  //如果读取的文件不是null     data = new StringBuffer(st);    else  //否则退出循环     break;   }   for(int j = str.length - 1; j >= 0; j--)   {    bw.write(str[j]);    bw.newLine();    bw.flush();   }   br.close();   bw.close();  }  catch(IOException e)  {   System.out.println(e);  } }  //获取文件内容的行数 public int countline(String pathreader)throws FileNotFoundException {  int count = 0;  File file = new File(pathreader);   FileInputStream fis = new FileInputStream(file);   Scanner scanner = new Scanner(fis);   while(scanner.hasNextLine())  {    scanner.nextLine();    count++;   }  return count; }  public static void main(String[] args) {  // TODO 自动生成方法存根  try  {   File_1_1 f1 = new File_1_1();   f1.getFile("/java/java1.txt","/java/java2.txt");  }  catch(NullPointerException e)  {   System.out.println(e);  } }}