利用org.apache.commons.io.FileUtils快速读写文件

   String fileName = "C://11.txt";
  File file = new File(fileName);
  String fileContent = "";
  try {
   fileContent = org.apache.commons.io.FileUtils.readFileToString(file, "GBK");
  } catch (IOException e) {
   e.printStackTrace();
  }
  fileContent +="Helloworld";
  try {
   org.apache.commons.io.FileUtils.writeStringToFile(file, fileContent, "GBK");
  } catch (IOException e) {
   e.printStackTrace();
  }

其他参考

Commons IO方便读写文件的工具类: http://laoyu.info/archives/282.html

Commons IO是apache的一个开源的工具包,封装了IO操作的相关类,使用Commons IO可以很方便的读写文件,url源代码等.

普通地读取一个网页的源代码的代码可能如下

   InputStream  in =   new   URL (   "http://laoyu.info"   ). openStream ( ) ;
    try   {
      InputStreamReader  inR =   new   InputStreamReader (  in   ) ;
      BufferedReader  buf =   new   BufferedReader (  inR   ) ;
      String  line ;
      while   (   (  line = buf. readLine ( )   )   !=   null   )   {
        System. out. println (  line   ) ;
      }
    }   finally   {
     in. close ( ) ;
    }

使用了Commons IO,则可以大大简化代码.如下:

   InputStream  in =   new   URL (   "http://laoyu.info"   ). openStream ( ) ;
    try   {
      System. out. println (  IOUtils. toString (  in   )   ) ;
    }   finally   {
     IOUtils. closeQuietly (in ) ;
    }

Commons IO里的常用类

FileUtils包含了文件操作的相关方法.
下面的代码用于读取磁盘上的某个文件:

File file = new File ( "c:/test.txt" ) ;
List lines = FileUtils. readLines (file, "UTF-8" ) ;

FileSystemUtils 可以获得指定磁盘路径的可用空间

long freeSpace = FileSystemUtils. freeSpace ( "d:/" ) ;

文件复制代码:

   File  src =   new   File ( "src.txt" ) ;
   File  dest =   new   File ( "dest.txt" ) ;
  FileUtils. copyFile (src, dest ) ;

补充:
方便地下载文件到本地

   InputStream  in =   new
   URL ( "http://www.baidu.com/img/baidu_logo.gif" ). openStream ( ) ;
      byte   [ ]  gif = IOUtils. toByteArray (in ) ;
      //IOUtils.write(gif,new FileOutputStream(new File("c:/test.gif")));
    FileUtils. writeByteArrayToFile ( new   File ( "c:/test.gif" ),gif ) ;
    IOUtils. closeQuietly (in ) ;

      输入流复制到输出流

   public   class  IoTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception {
           // TODO Auto-generated method stub
          Writer write =  new  FileWriter( "c:\\kk.dat" );
          InputStream ins =  new  FileInputStream( new  File( "c:\\text.txt" ));
          IOUtils.copy(ins, write);
          write.close();
          ins.close();
      }
  }

        文本写入指定文件

   public   class  FileWirterTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception{
           // TODO Auto-generated method stub
          String name =  "my name is panxiuyan" ;
          File file =   new  File( "c:\
ame.txt" );
          FileUtils.writeStringToFile(file, name);
      }
  }

            将输入流转换成文本

   public   class  URLIoTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception {
           // TODO Auto-generated method stub
          URL url =  new  URL( "http://www.dimurmill.com" );
          InputStream ins = url.openStream();
          String contents = IOUtils.toString(ins, "UTF-8" );
          System.out.println(  "Slashdot: "  + contents );
      }
  }

        关闭相关流

   public   class  IoCloseTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args) {
           // TODO Auto-generated method stub
          File file =  null ;
          InputStream ins =  null ;
           try {
              file =  new  File( "C:\\Test.java" );
              ins =  new  FileInputStream(file);
          } catch (Exception e){
              e.printStackTrace();
          } finally {
              IOUtils.closeQuietly(ins);
          }
      }
  }

            文件复制

   public   class  FileCopyTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception{
           // TODO Auto-generated method stub
          File srcfile =  new  File( "c:\\Test.java" );
          File destfile =  new  File( "c:\\Test.java.bak" );
          FileUtils.copyFile(srcfile, destfile);
      }
  }

        文件复制指定的目录

   public   class  FileCopyTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception{
           // TODO Auto-generated method stub
          File srcfile =  new  File( "c:\\Test.java" );
          File destDir =  new  File( "D:\\" );
          FileUtils.copyFileToDirectory(srcfile, destDir);
      }
  }

        网络流保存为文件

   public   class  URLToFileTest {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception{
           // TODO Auto-generated method stub
          URL url =  new  URL( "http://www.163.com" );
          File file =  new  File( "c:\\163.html" );
          FileUtils.copyURLToFile(url, file);
      }
  }

            文件目录操作

   public   class  DirOper {
       /**
        * @param args
        */
       public   static   void  main(String[] args)  throws  Exception {
           // TODO Auto-generated method stub
          File dir =  new  File( "c:\\test" );
          FileUtils.cleanDirectory(dir); //清空目录下的文件
          FileUtils.deleteDirectory(dir); //删除目录和目录下的文件
      }
  }

            目录大小

   long  size = FileUtils.sizeOfDirectory(dir);

            目录操作

   File testFile =  new  File(  "testFile.txt"  );
        //如果不存在,新建
       // 如果存在,修改文件修改时间
      FileUtils.touch( testFile );

            记录流的读取写入字节数

   File test =  new  File(  "test.dat"  );
   //输出流的统计
  CountingOutputStream countStream =  null ;
   //输入流的统计
   //CountingInputStream countStream = null;
   try  {
      FileOutputStream fos =  new  FileOutputStream( test );
      countStream =  new  CountingOutputStream( fos );
      countStream.write(  "Hello" .getBytes( ) );
  }  catch ( IOException ioe ) {
      System.out.println(  "Error writing bytes to file."  );
  }  finally  {
      IOUtils.closeQuietly( countStream );
  }
   if ( countStream !=  null  ) {
       int  bytesWritten = countStream.getCount( );
      System.out.println(  "Wrote "  + bytesWritten +  " bytes to test.dat"  );
  }

            相同的内容写入不同的文本

   File test1 =  new  File( "split1.txt" );
  File test2 =  new  File( "split2.txt" );
  OutputStream outStream =  null ;
   try  {
      FileOutputStream fos1 =  new  FileOutputStream( test1 );
      FileOutputStream fos2 =  new  FileOutputStream( test2 );
       //包含不同的文本
      outStream =  new  TeeOutputStream( fos1, fos2 );
      outStream.write(  "One Two Three, Test" .getBytes( ) );
      outStream.flush( );
  }  catch ( IOException ioe ) {
      System.out.println(  "Error writing to split output stream"  );
  }  finally  {
      IOUtils.closeQuietly( outStream );
  }

                                                ----------------------------
原文链接:https://blog.csdn.net/weixin_30765319/article/details/99967288

程序猿的技术大观园：www.javathinker.net

[这个贴子最后由 flybird 在 2020-01-09 22:45:35 重新编辑]