java操作txt文件

      java操作文本文件个人认为最繁杂的是修改操作！需要重写整个文本！好了不说了先贴代码！

public class txtfile {

  public void txtfileQ() throws IOException{       //txt文件的查询
  FileReader fr =new FileReader("c://a.txt");
  BufferedReader br = new BufferedReader(fr);
  String Line=br.readLine();//从文件读取一行字符串
        //  依据读取到的整行字符串是否不为空，来判断是够到达文件结尾
  for (int i=0;Line !=null;i++){
   if(Line.indexOf("测试")>-1){         // 使用indexof来实现模糊查询
   System.out.println(Line+"1111111");
   }
   Line= br.readLine();
  }
  br.close();//关闭BufferedReader对象
  fr.close();//关闭文件
 }

//写txt文件  txtfile.getProperty("txtlist")为获得配置文件内的文件路径
 public void txtfileW() throws IOException{
  txtfile txtfile = new txtfile();
  FileWriter fw=new FileWriter(txtfile.getProperty("txtlist"),true);//建立FileWriter对象，并实例化fw
//  将字符串写入文件
  for (int i=0;i<20;i++){
  fw.write("这是本文档的第"+i+"行"+"\r\n");
  }
  fw.write("测试耗费时间！");
  fw.close();
 }

//删除文件一行操作，可以类比为修改替换操作  txtfile.getProperty("newline")为配置文件内定义的回车换行符
 public void txtfileD() throws IOException{
  String line = "";
  txtfile txtfile = new txtfile();
        try {
            File file = new File(txtfile.getProperty("txtlist"));
            FileInputStream fis = new FileInputStream(file);
            InputStreamReader isr = new InputStreamReader(fis);
            BufferedReader br = new BufferedReader(isr);
            StringBuffer buf = new StringBuffer();
            // 保存该行前面的内容
            for (int j = 1; (line = br.readLine()) != null
                    && !line.equals("这是本文档的第6行"); j++) {
                buf = buf.append(line);
                buf = buf.append(txtfile.getProperty("newline"));
            }
            // 将内容替换为空
            buf = buf.append("");
            // 保存该行后面的内容
            while ((line = br.readLine()) != null) {
                buf = buf.append(line);
                buf = buf.append(txtfile.getProperty("newline"));
            }
            br.close();
            FileOutputStream fos = new FileOutputStream(file);
            PrintWriter pw = new PrintWriter(fos);
            pw.write(buf.toString().toCharArray());
            pw.flush();
            pw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
 }

//txt文件增加一行，追加到最后一行
 public void txtfileA() throws IOException{
  txtfile txtfile = new txtfile();
  RandomAccessFile rf=new RandomAccessFile(txtfile.getProperty("txtlist"),"rw");
//  定义一个类RandomAccessFile的对象，并实例化。txtfile.getProperty("txtlist")为获得配置文件内的文件路径
  rf.seek(rf.length());
  rf.write("追加到文件最后一行！".getBytes());
  rf.close();//关闭文件流
 }

//读取配置文件获得文件路径
 public String getProperty(String propertyname){
  String propertyvalue = null;
  Properties pro = new Properties ();
  try {
   FileInputStream fin = new FileInputStream("D://workspace//YNSMIMPL//WebRoot//WEB-INF//txt.properties");
   pro.load(fin);
   propertyvalue = pro.getProperty(propertyname);
  } catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  return propertyvalue;
 }
 /*
  * 遍历文件夹内文件并判断文件大小！
  */
 public String SelectPath(String path){
  File dir = new File(path);
  File[] tempf=dir.listFiles();
        String filenameN="";
        if(dir.isDirectory()){
         if(tempf.length>1){
         for (int n=1;n<tempf.length;n++){
                filenameN = path+"\\"+tempf[0].getName();
                   File a = new File(filenameN);
             File b = new File(path+"\\"+tempf[n].getName());
             if(a.length()>b.length()){
              filenameN = path+"\\"+tempf[n].getName();
             }else{
              filenameN = path+"\\"+tempf[0].getName();
             }
             }
            }else{
             filenameN = path+"\\"+tempf[0].getName();
            }
        }
        System.out.println(filenameN);
        return filenameN;
 }