Java IO流各种使用方式总结

Java IO流各种使用方式总结

      ①针对普通文本的复制常用方式：FileInputStream fis = new FileInputStream(tempFile);
FileOutputStream fos = new FileOutputStream(new File(dest));
byte[] buff = new byte[1024];
int len = -1;
while ((len = fis.read(buff)) != -1) {
fos.write(buff, 0, len);
}
fis.close();
fos.flush();
fos.close();②效率比较高的复制方式：第一种用法/*2、用新IO里的FileChannel方式*/
FileChannel srcCh = new FileInputStream(src).getChannel();
FileChannel destCh = new FileOutputStream(dest).getChannel();
destCh.transferFrom(srcCh, 0, srcCh.size());
srcCh.close();
destCh.close();第二种用法 fIn = new FileInputStream(args[0]);
fOut = new FileOutputStream(args[1]);
fIChan = fIn.getChannel();
fOChan = fOut.getChannel();
fSize = fIChan.size();
mBuf = fIChan.map(FileChannel.MapMode.READ_ONLY, 0, fSize);
fOChan.write(mBuf); // this copies the file
fIChan.close();
fIn.close();③删除N天前的文件（定期删备份文件）比如删除目录中超过一个星期的所有文本文件/**
  * 删除备份数据库文件 注意：指定删除的文件为最后一次修改的文件日期，不是按照文件名也不是
  * 文件所创建的日期。指定的path必须是目录名，否则函数不会执行并且没有返回值。
  *
  * @param day
  *            天数
  * @param path
  *            路径目录名
  */
public static void deletedb(int day, String path) {
  long datenum;
  Date date;
  Date datenow;
  Calendar cal = Calendar.getInstance();
  Calendar calnow = Calendar.getInstance();
  File filepath = CsvOperate.filepathpreproc(path);
  File[] files;
  if (filepath.exists()) {
   if (filepath.isDirectory()) {
    files = filepath.listFiles();
    for (int i = 0; i < files.length; i++) {
     date = new Date(files[i].lastModified());
     datenow = new Date();
     cal.setTime(date);
     calnow.setTime(datenow);
     int dec = calnow.get(Calendar.DAY_OF_YEAR)
       - cal.get(Calendar.DAY_OF_YEAR);
     // 删除指定日期的文件
     if (dec >= day) {
      files[i].delete();
     }
    } // end for
   } // end if (filepath.isdirectory())
  } // end if (filepath.exists())
}
/**
  * 文件路径预处理，将windows或unix like 路径转化为统一的unix like路径，如果用户输入有误则返回null
  *
  * @param pathstr
  * @return
  */
public static File filepathpreproc(String pathstr) {
  pathstr = pathstr.replaceAll("    \\\\", "/").trim();
  // system.out.println(pathstr);
  Pattern p = Pattern.compile("(^\\.|^/|^[a-za-z])?:?/.+(/$)?");
  Matcher m = p.matcher(pathstr);
  // 不符合要求直接返回
  if (!m.matches()) {
   return null;
  }
  // 这里开始文件名已经符合要求
  File path = new File(pathstr);
  return path;
}④另奉完整复制示例public class PrintFiles {
String sourcDir = "";
String desDir = "";
File file = null;
String logFile = "";
public PrintFiles(String root,String sourcDir,String desDir,String logFile){
  this.file = new File(root);
  this.sourcDir = sourcDir;
  this.desDir = desDir;
  this.logFile = logFile;
}
/*
  * @method检查指定的源目的文件夹是否存在
  */
public int checkDirName(){
  File [] fileArray = file.listFiles();
  boolean flag_desDir = false;
  boolean flag_sourceDir = false;
  for(int i=0;i<fileArray.length;i++){
   if(fileArray[i].getName().equalsIgnoreCase(sourcDir)){
    flag_sourceDir = true;
   }
   if(fileArray[i].getName().equalsIgnoreCase(desDir)){
    flag_desDir = true;
   }
   if(flag_desDir&&flag_sourceDir){
    break;
   }
  }
  if(!flag_desDir){
   File d = new File(file.toString().replace(&apos;\\&apos;, &apos;/&apos;)+desDir);
   d.mkdir();
  }
  if(!flag_sourceDir){
   return 1;
  }
  return 2;
}
/*
  * @method执行文件拷贝功能
  */
    public String  copyFiles(){  
     String root = file.toString().replace( &apos;\\&apos; , &apos;/&apos;);
     File [] fileArray = new File(root+sourcDir).listFiles();
     for(int i=0;i<fileArray.length;i++){
      String filename = fileArray[i].getName();
      if(filename.endsWith(".txt")){
       try {
        FileInputStream fileInputStream = new FileInputStream(root+sourcDir+"/"+filename);
        FileOutputStream fileOutputStream = new FileOutputStream(root+desDir+"/"+filename);
        byte [] b = new byte[1024*5];
        int len;
        while((len=fileInputStream.read(b))!=-1){
         fileOutputStream.write(b, 0, len);
        }
        fileOutputStream.flush();
        fileOutputStream.close();
        fileInputStream.close();
        writeToLog(root+"/"+logFile, filename);
       
       } catch (FileNotFoundException e) {
        e.printStackTrace();
        return "FileNotFoundException";
       }catch(IOException e){
        e.printStackTrace();
        return "IOException";
       }}}
     return "OK";   
    }
/*
  * @method写入日志
  */
    public String writeToLog(String logName,String data){
     File logfile = new File(logName);
     if(!logfile.exists()){
      try{
       logfile.createNewFile();
      }catch(IOException e){
       e.printStackTrace();
      }
     }else{
      StringBuffer sb = new StringBuffer();     
      try{
       if (data != null && data.length() > 0){       
        BufferedReader br = new BufferedReader(
          new InputStreamReader(
            new FileInputStream(logfile)));
        String tempdata = null;
        while((tempdata=br.readLine())!= null){
         sb.append(tempdata+"\n");
        }
        br.close();
       }
       PrintWriter pw = new PrintWriter(new OutputStreamWriter(new FileOutputStream(logfile)), true);
       pw.write(sb.toString());
       pw.write(data);
       pw.flush();
       pw.close();
      }catch(Exception e){
       e.printStackTrace();
      }
     }
     return "";
    }
    public   static   void   main(String[]   args)   throws   Exception   {  
     String copy = "";
     PrintFiles pf = new  PrintFiles("e:/","wx1","wx2","ss.log"); 
        int i = pf.checkDirName();
        if(i==1){
         System.out.println("源文件夹不存在");
        }else if(i==2){
         System.out.println("完成检查");
         copy = pf.copyFiles();
         System.out.println("拷贝检查");
        }    
        if(copy.equalsIgnoreCase("FileNotFoundException")){
         System.out.println("FileNotFoundException");
        }else if(copy.equalsIgnoreCase("IOException")){
         System.out.println("IOException");
        }
    }
}