java如何修改一个文件的内容呢？

实现思路:
    1.使用两个Buffer，一个作为读Buffer，一个作为写Buffer
	2.将读Buffer中的内容，经过变更后放入到写Buffer中
	3.对写buffer产生的文件，进行变更名称后，作为修改后的文件输出

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class replaceFileContents {
   public static void main(String[] args) {
     new ReplaceFileContents().replace();
   }

   public void replace() {
      String oldFileName = "source.txt";
      String tmpFileName = "tmp_source.txt";

      BufferedReader br = null;
      BufferedWriter bw = null;
      try {
         br = new BufferedReader(new FileReader(oldFileName));
         bw = new BufferedWriter(new FileWriter(tmpFileName));
         String line;
         while ((line = br.readLine()) != null) {
            if (line.contains("java265.com"))
               line = line.replace("java265.com", ""+System.currentTimeMillis());
            bw.write(line+"\n");
         }
      } catch (Exception e) {
         return;
      } finally {
         try {
            if(br != null)
               br.close();
         } catch (IOException e) {
            //
         }
         try {
            if(bw != null)
               bw.close();
         } catch (IOException e) {
            //
         }
      }
      // Once everything is complete, delete old file..
      File oldFile = new File(oldFileName);
      oldFile.delete();

      // And rename tmp file's name to old file name
      File newFile = new File(tmpFileName);
      newFile.renameTo(oldFile);

   }
}