CopyUtils执行从read到write的数据拷贝

Commons IO提供了org.apache.commons.io.CopyUtils类来将某个InputStream,Reader,byte[]数据或字符串的内容拷贝到OutputStream或Writer.

Writer writer = new FileWriter( "test.dat" );  
InputStream inputStream =
            getClass( ).getResourceAsStream("./test.resource");  
CopyUtils.copy( inputStream, writer );  
writer.close( );  
inputStream.close( );  

Writer writer = new FileWriter( "test.dat" ); 
InputStream inputStream = 
        getClass( ).getResourceAsStream("./test.resource"); CopyUtils.copy( inputStream, writer ); 
writer.close( ); 
inputStream.close( ); 

如果需要把信息从Reader或InputStream拷贝到字符串中,请使用IOUtils.toString()方法.

InputStream inStream = url.openStream( );  
String contents = IOUtils.toString( inStream );  

InputStream inStream = url.openStream( ); 
String contents = IOUtils.toString( inStream ); 

通过org.apache.commons.io.IOUtils,你可以很好地关闭某个InputStream,OutputStream,Reader或Writer,而不必担心null或IOException.

 try {  
   File file = new File( "test.dat" );  
   reader = new FileReader( file );  
   result = CopyUtils.toString( reader );  
   } catch( IOException ioe ) {  
   System.out.println("Unable to copy file test.dat to a String." );  
   } finally {  
     IOUtils.closeQuietly( reader );  
   }  

  try { 
    File file = new File( "test.dat" ); 
    reader = new FileReader( file ); 
    result = CopyUtils.toString( reader ); 
  } catch( IOException ioe ) { 
    System.out.println("Unable to copy file test.dat to a String." ); 
  } finally { 
    IOUtils.closeQuietly( reader ); 
  } 

使用FileUtils.byteCountToDisplaySize()生成一个字符串,该字符串含有有一个近似的比较好理解的文件的相对大小的值.

   File file = new File("project.xml");  
   long bytes = file.length( );  
   String display = FileUtils.byteCountToDisplaySize( bytes );  

   File file = new File("project.xml"); 
   long bytes = file.length( ); 
   String display = FileUtils.byteCountToDisplaySize( bytes ); 

如果需要将一个文件拷贝为另一个文件,或者需要将某个文件拷贝到某一个目录中,可以使用如下的代码:
拷贝为另一个文件:

     File src = new File( "test.dat" );  
    file dest = new File( "test.dat.bak" );  
    FileUtils.copyFile( src, dest );  

    File src = new File( "test.dat" ); 
    file dest = new File( "test.dat.bak" ); 
    FileUtils.copyFile( src, dest ); 

拷贝到某一个目录:

   File src = new File( "test.dat" );  
   File dir = new File( "./temp" );  
   FileUtils.copyFileToDirectory( src, dir );  

    File src = new File( "test.dat" ); 
    File dir = new File( "./temp" ); 
    FileUtils.copyFileToDirectory( src, dir ); 

使用Commons IO,你也可以很方便把字符串的内容写入文件中去,具体的过程不用怎么理会:

   String string = "Blah blah blah";  
   File dest = new File( "test.tmp" );  
   FileUtils.writeStringToFile( dest, string);  

  String string = "Blah blah blah"; 
  File dest = new File( "test.tmp" ); 
  FileUtils.writeStringToFile( dest, string); 

当然,有另外的一个功能,可以将URL的内容存入文件中去:

   URL src = new URL( "http://www.nytimes.com" );  
   File dest = new File( "times.html" );  
   FileUtils.copyURLToFile( src, dest );  

    URL src = new URL( "http://www.nytimes.com" ); 
    File dest = new File( "times.html" ); 
    FileUtils.copyURLToFile( src, dest ); 

如果你需要删除一个目录下的所有内容(包括其目录),可以这样做:

    File dir = new File( "temp" );  
    FileUtils.deleteDirectory( dir );  

    File dir = new File( "temp" ); 
    FileUtils.deleteDirectory( dir ); 

如果只想清空目录下所有内容,并不删除该目录,可以这样写:

FileUtils.cleanDirectory( dir );

很简单地,可以得到一个目录的大小:

   File dir = new File( "temp" );  
   long dirSize = FileUtils.sizeOfDirectory( );  

   File dir = new File( "temp" ); 
   long dirSize = FileUtils.sizeOfDirectory( ); 

如果你想得到某个目录下所有以.txt结尾的文件,可以如下这样做:

   import java.io.FilenameFilter;  
   import org.apache.commons.io.filefilter.SuffixFileFilter;  
   import org.apache.commons.lang.ArrayUtils;  
      
   File rootDir = new File(".");  
   FilenameFilter fileFilter = new SuffixFileFilter(".txt");  
   String[] txtFiles = rootDir.list( fileFilter );  
   System.out.println( ArrayUtils.toString( txtFiles ) );  

   import java.io.FilenameFilter; 
   import org.apache.commons.io.filefilter.SuffixFileFilter; 
   import org.apache.commons.lang.ArrayUtils; 

   File rootDir = new File("."); 
   FilenameFilter fileFilter = new SuffixFileFilter(".txt"); 
   String[] txtFiles = rootDir.list( fileFilter ); 
   System.out.println( ArrayUtils.toString( txtFiles ) ); 

举另一个例子,怎样列出目录中以.htm和.html结尾的文件

    import org.apache.commons.io.filefilter.AndFileFilter;  
    import org.apache.commons.io.filefilter.DirectoryFileFilter;  
    import org.apache.commons.io.filefilter.IOFileFilter;  
    import org.apache.commons.io.filefilter.NotFileFilter;  
    import org.apache.commons.io.filefilter.OrFileFilter;  
    import org.apache.commons.io.filefilter.SuffixFileFilter;  
    import org.apache.commons.lang.ArrayUtils;  
      
    IOFileFilter htmlFilter =   
       new OrFileFilter( new SuffixFileFilter("htm"),new SuffixFileFilter("html") ); //复合两个SuffixFileFilter  
    IOFileFilter notDirectory = new NotFileFilter( DirectoryFileFilter.INSTANCE );    //拒绝选择目录  
     FilenameFilter fileFilter = new AndFileFilter( htmlFilter, notDirectory );  
    String[] htmlFiles = rootDir.list(fileFilter);  
    System.out.println( ArrayUtils.toString( htmlFiles ));  

import org.apache.commons.io.filefilter.AndFileFilter; 
import org.apache.commons.io.filefilter.DirectoryFileFilter; 
import org.apache.commons.io.filefilter.IOFileFilter; 
import org.apache.commons.io.filefilter.NotFileFilter; 
import org.apache.commons.io.filefilter.OrFileFilter; 
import org.apache.commons.io.filefilter.SuffixFileFilter; 
import org.apache.commons.lang.ArrayUtils; 

IOFileFilter htmlFilter = 
    new OrFileFilter( new SuffixFileFilter("htm"),new SuffixFileFilter("html") ); //复合两个SuffixFileFilter 
IOFileFilter notDirectory = new NotFileFilter( DirectoryFileFilter.INSTANCE );    //拒绝选择目录 
FilenameFilter fileFilter = new AndFileFilter( htmlFilter, notDirectory ); 
String[] htmlFiles = rootDir.list(fileFilter); 
System.out.println( ArrayUtils.toString( htmlFiles ));