/* XXL: The eXtensible and fleXible Library for data processing
Copyright (C) 2000-2011 Prof. Dr. Bernhard Seeger
Head of the Database Research Group
Department of Mathematics and Computer Science
University of Marburg
Germany
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; If not, see <http://www.gnu.org/licenses/>.
http://code.google.com/p/xxl/
*/
package xxl.core.io.converters;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
/**
* This class provides a converter that is able to read and write arrays of
* <code>String</code> objects. First the converter reads or writes the length
* of the <code>String</code> array. Thereafter the <code>String</code> objects
* are read or written.
*
* <p>Example usage (1).
* <code><pre>
* // create a string array
*
* String[] array = {"This", "is", "a", "String", "array"};
*
* // create a byte array output stream
*
* ByteArrayOutputStream output = new ByteArrayOutputStream();
*
* // write array to the output stream
*
* StringArrayConverter.DEFAULT_INSTANCE.write(new DataOutputStream(output), array);
*
* // create a byte array input stream on the output stream
*
* ByteArrayInputStream input = new ByteArrayInputStream(output.toByteArray());
*
* // reset the array
*
* array = null;
*
* // read array from the input stream
*
* array = StringArrayConverter.DEFAULT_INSTANCE.read(new DataInputStream(input));
*
* // print the array
*
* for (String string : array)
* System.out.println(string);
*
* // close the streams after use
*
* input.close();
* output.close();
* </pre></code></p>
*
* @see DataInput
* @see DataOutput
* @see IOException
*/
public class StringArrayConverter extends Converter<String[]> {
/**
* This instance can be used for getting a default instance of a string
* array converter. It is similar to the <i>Singleton Design Pattern</i>
* (for further details see Creational Patterns, Prototype in <i>Design
* Patterns: Elements of Reusable Object-Oriented Software</i> by Erich
* Gamma, Richard Helm, Ralph Johnson, and John Vlissides) except that
* there are no mechanisms to avoid the creation of other instances of a
* string array converter.
*/
public static final StringArrayConverter DEFAULT_INSTANCE = new StringArrayConverter();
/**
* Reads an array of <code>String</code> objects from the specified data
* input and returns the restored <code>String</code> array.
*
* <p>When the specified <code>string</code> array is <code>null</code>
* this implementation returns a new array of <code>String</code> object,
* otherwise the size of the specified string array has to be sufficient.
* For reading the single <code>String</code> objects from the specified
* data input, a string converter is used.</p>
*
* @param dataInput the stream to read the <code>String</code> array from.
* @param object the <code>String</code> array to be restored.
* @return the read array of <code>String</code> objects.
* @throws IOException if I/O errors occur.
*/
@Override
public String[] read(DataInput dataInput, String[] object) throws IOException{
int length = dataInput.readInt();
if (object == null)
object = new String[length];
for (int i = 0; i < object.length; i++)
object[i] = StringConverter.DEFAULT_INSTANCE.read(dataInput);
return object;
}
/**
* Writes the specified array of <code>String</code> objects to the
* specified data output.
*
* <p>This implementation first writes the length of the array to the data
* output. Thereafter the <code>String</code> objects are written by
* calling the <code>write</code> method of a string converter.</p>
*
* @param dataOutput the stream to write the <code>String</code> array to.
* @param object the <code>String</code> array that should be written to
* the data output.
* @throws IOException includes any I/O exceptions that may occur.
*/
@Override
public void write(DataOutput dataOutput, String[] object) throws IOException{
dataOutput.writeInt(object.length);
for (String string : object)
StringConverter.DEFAULT_INSTANCE.write(dataOutput, string);
}
}