Java增、删、改、查txt文件

1.txt

zhang,f3d8071f8f789df766588469ecc6b1f5;

package readtext;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

publicclass ReadText {
 

 /**
  * @param args
 * @throws IOException
  */
 publicstaticvoid main(String[] args) throws IOException {
  String FileName="C:/1.txt";
   File f=new File(FileName);
   char act='u';
   String UserName="zhang";
   String SID="f3d8071f8f789df766588469ecc6b1f5";
  switch(act)
     {
         case'c':
          ReadText.CreateTxt(f);
             break;
         case'r':
          ReadText.ReadTxt(f);
             break;
         case'w':
          ReadText.WriteTxt(f, SID,UserName);
             break;
         case'd':
          ReadText.DeleteTxt(f);
             break;
         case'u':
          ReadText.UpdateTxt(f, SID);
             break;

     }
  }
  //新建文件
publicstaticvoid CreateTxt(File f){
  if(f.exists())
  {
   System.out.println("文件已存在");   
  }
  else{
   try{
    // 新建text文件
   f.createNewFile();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
  }
  //删除文件
publicstaticvoid DeleteTxt(File f){
   if(f.exists()){
    f.delete();
    System.out.println("文件delete");
   }
   else{
    System.out.println("文件不存在");
   }
  }
  //读文件
publicstaticvoid ReadTxt(File f) throws IOException{
   String read;
   String readStr ="";
   if(f.exists()){
    BufferedReader br =new BufferedReader(new FileReader(f));
     while ((read = br.readLine()) !=null) {
              readStr = readStr + read;
     }
     br.close();
    System.out.println("文件内容是:"+"\r\n"+ readStr);
   }
   else{
    System.out.println("文件不存在!");
   }
  }
  publicstaticint CheckUser(File f,String SID) throws IOException{
   int isOk=0;
   String read;
   String readStr ="";
   if(!f.exists()){
    f.createNewFile();
   }
   BufferedReader br =new BufferedReader(new FileReader(f));
   while ((read = br.readLine()) !=null) {
          readStr = readStr + read;
   }
  br.close();
  if(readStr==""||readStr==null){
   isOk=1;
   System.out.println("null or ''");
  }else{
   String[] str1=readStr.split(";");
   for(int i=0;i<str1.length;i++){
    String[] str_sid=str1[i].split(",");
    //System.out.println(str1[i]);
if(str_sid[1].equals(SID)){
     System.out.println("SID--------"+SID);
     System.out.println("str_sid[1]------"+str_sid[1]);
     isOk=0;
    }
    else{
     isOk=1;
    }
   
   }
  }
  return isOk;
  }
  //写文件
publicstaticvoid WriteTxt(File f,String SID,String UserName) throws IOException{
   String read;
   String readStr ="";
   if(!f.exists()){
    f.createNewFile();
   }
   BufferedReader br =new BufferedReader(new FileReader(f));
   while ((read = br.readLine()) !=null) {
          readStr = readStr + read;
   }
  br.close();
  int l=CheckUser(f, SID);
  if(l==1){
   PrintWriter bf=new PrintWriter(new FileWriter(f));
   String newstr=UserName+","+SID+";";
    String s=readStr+newstr;
   bf.print(s);
   bf.close();
   System.out.println("输出到文件成功!"+s);
  }
  else{
   System.out.println("用户已存在!"+SID);
  }
  }
  //修改文件
publicstaticvoid UpdateTxt(File f,String SID) throws IOException{
   String read;
   String readStr ="";
   if(!f.exists()){
    System.out.println("文件不存在!");
   }
   else{
    BufferedReader br =new BufferedReader(new FileReader(f));
    while ((read = br.readLine()) !=null) {
             readStr = readStr + read;
    }
    br.close();
    String[] str1=readStr.split(";");
    for(int i=0;i<str1.length;i++){
     String[] str_sid=str1[i].split(",");
     //System.out.println(str1[i]);
if(str_sid[1].equals(SID)){
      PrintWriter bf=new PrintWriter(new FileWriter(f));
      String s=readStr.replace(str1[i]+";", "");
      bf.print(s);
      bf.close();
      System.out.println("修改文件成功!");
      break;
     }
    }
   }
  }
}