commons FileUtils 学习一

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

1. InputStream in = new URL( "http://laoyu.info" ).openStream();
2.  try {
3.    InputStreamReader inR = new InputStreamReader( in );
4.    BufferedReader buf = new BufferedReader( inR );
5.    String line;
6.    while ( ( line = buf.readLine() ) != null ) {
7.      System.out.println( line );
8.    }
9.  } finally {
10.    in.close();
11.  }

使用了Commons IO,则可以大大简化代码.如下:

1. InputStream in = new URL( "http://laoyu.info" ).openStream();
2.  try {
3.    System.out.println( IOUtils.toString( in ) );
4.  } finally {
5.    IOUtils.closeQuietly(in);
6.  }

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:

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

FileSystemUtils 可以获得指定磁盘路径的可用空间

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

文件复制代码:

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

补充:
方便地下载文件到本地

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

 

 

分享 commons io 工具类 代码:http://www.javaeye.com/topic/575996

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:\\name.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 );

}