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See:
Description
Class Summary | |
AndFileFilter | Accepts a selection if it is acceptable to both of two FilenameFilter s. |
ClassLoaderObjectInputStream | A special ObjectInputStream to handle highly transient classes hosted by Avalon components that are juggling many classloaders. |
DirectoryFileFilter | This filter accepts File s that are directories. |
EndianUtil | Utility code for dealing with different endian systems. |
ExtensionFileFilter | This filters files based on the extension (what the filename ends with). |
FileUtil | This class provides basic facilities for manipulating files and file paths. |
InvertedFileFilter | This takes a FilenameFilter |
IOUtil | General IO Stream manipulation. |
OrFileFilter | Accepts a selection if it is acceptable to either of two FilenameFilter s. |
PrefixFileFilter | This filters filenames for a certain prefix. |
SwappedDataInputStream | DataInput for systems relying on little endian data formats. |
Utility code for IO operations.
The org.apache.avalon.excalibur.io
package contains utility code for file-
and stream-based IO operation. There are three main types of class:
The Java API defines an interface FilenameFilter
, which is used to filter
directory listings. This is commonly used in the File.list(java.io.FilenameFilter)
method, and in java.awt.FileDialog
.
There are three "primitive" FilenameFilters:
DirectoryFilter | Only accept directories |
PrefixFileFilter | Filter based on prefix |
ExtensionFileFilter | Filter based on extension |
And there are three "boolean" FilenameFilters:
AndFileFilter | Accept if two subfilters both accept |
InvertedFileFilter | Accept if a subfilter rejects |
OrFileFilter | Accept if either of two subfilters accepts |
These boolean FilenameFilters can be nested, to allow arbitrary expressions. For example, here is how one could print all non-directory files in the current directory, starting with "A", and ending in ".java" or ".class":
File dir = new File("."); String[] files = dir.list( new AndFileFilter( new AndFileFilter( new PrefixFileFilter("A"), new OrFileFilter( new ExtensionFileFilter(".class"), new ExtensionFileFilter(".java") ) ), new InvertedFileFilter( new DirectoryFileFilter() ) ) ); for ( int i=0; i<files.length; i++ ) { System.out.println(files[i]); }
The IOUtil class contains a comprehensive set of static methods for copying from:
String
byte[]
InputStream
Reader
String
byte[]
OutputStream
Writer
As an example, consider the task of reading bytes from a URL, and printing them. This would typically done like this:
import java.net.URL; import java.io.*; public class ManualCopy { public static void main(String args[]) throws IOException { InputStream in = new URL( "http://jakarta.apache.org" ).openStream(); InputStreamReader inR = new InputStreamReader( in ); BufferedReader buf = new BufferedReader( inR ); String line; while ( ( line = buf.readLine() ) != null ) { System.out.println( line ); } in.close(); } }
With the IOUtil class, that could be done with:
import java.net.URL; import java.io.*; import org.apache.avalon.excalibur.io.IOUtil; public class IOUtilCopy { public static void main(String args[]) throws IOException { InputStream in = new URL( "http://jakarta.apache.org" ).openStream(); System.out.println( IOUtil.toString( in ) ); in.close(); } }
In certain application domains, such IO operations are common, and this class can save a great deal of time.
For utility code such as this, flexibility and speed are of primary importance. In IOUtil, each kind of copy method has a variant which allows the buffer size to be set. For methods that convert bytes to chars, the encoding method may also be set.
The FileUtil class contains methods for retrieving different components of a file path (directory name, file base name, file extension), methods for copying Files to other files and directories, and methods for deleting and cleaning directories. For more information, see the class description
Different computer architectures adopt different conventions for byte ordering. In so-called "Little Endian" architectures (eg Intel), the low-order byte is stored in memory at the lowest address, and subsequent bytes at higher addresses. For "Big Endian" architectures (eg Motorola), the situation is reversed.
There are two classes in this package of relevance:
DataInput
interface. With this, one can read
data from files of non-native Endian-ness.For more information, see http://www.cs.umass.edu/~verts/cs32/endian.html.
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