/* 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
* <code>Double</code> objects. In addition to the read and write methods that
* read or write <code>Double</code> objects this class contains
* <code>readDouble</code> and <code>writeDouble</code> methods that convert
* the <code>Double</code> object after reading or before writing it to its
* primitive <code>double</code> type.
*
* <p>Example usage (1).
* <code><pre>
* // create a byte array output stream
*
* ByteArrayOutputStream output = new ByteArrayOutputStream();
*
* // write a Double and a double value to the output stream
*
* DoubleConverter.DEFAULT_INSTANCE.write(new DataOutputStream(output), 2.7236512);
* DoubleConverter.DEFAULT_INSTANCE.writeDouble(new DataOutputStream(output), 6.123853);
*
* // create a byte array input stream on the output stream
*
* ByteArrayInputStream input = new ByteArrayInputStream(output.toByteArray());
*
* // read a double value and a Double from the input stream
*
* double d1 = DoubleConverter.DEFAULT_INSTANCE.readDouble(new DataInputStream(input));
* Double d2 = DoubleConverter.DEFAULT_INSTANCE.read(new DataInputStream(input));
*
* // print the value and the object
*
* System.out.println(d1);
* System.out.println(d2);
*
* // close the streams after use
*
* input.close();
* output.close();
* </pre></code></p>
*
* @see DataInput
* @see DataOutput
* @see IOException
*/
public class DoubleConverter extends FixedSizeConverter<Double> {
/**
* This instance can be used for getting a default instance of a double
* 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
* double converter.
*/
public static final DoubleConverter DEFAULT_INSTANCE = new DoubleConverter();
/**
* This field contains the number of bytes needed to serialize the
* <code>double</code> value of a <code>Double</code> object. Because this
* size is predefined it must not be measured each time.
*/
public static final int SIZE = 8;
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
public DoubleConverter() {
super(SIZE);
}
/**
* Reads the <code>double</code> value for the specified
* (<code>Double</code>) object from the specified data input and returns
* the restored object.
*
* <p>This implementation ignores the specified object and returns a new
* <code>Double</code> object. So it does not matter when the specified
* object is <code>null</code>.</p>
*
* @param dataInput the stream to read the <code>double</code> value from
* in order to return a <code>Double</code> object.
* @param object the (<code>Double</code>) object to be restored. In this
* implementation it is ignored.
* @return the read <code>Double</code> object.
* @throws IOException if I/O errors occur.
*/
@Override
public Double read(DataInput dataInput, Double object) throws IOException {
return dataInput.readDouble();
}
/**
* Reads the <code>double</code> value from the specified data input and
* returns it.
*
* <p>This implementation uses the read method and converts the returned
* <code>Double</code> object to its primitive <code>double</code>
* type.</p>
*
* @param dataInput the stream to read the <code>double</code> value from.
* @return the read <code>double</code> value.
* @throws IOException if I/O errors occur.
*/
public double readDouble(DataInput dataInput) throws IOException {
return read(dataInput);
}
/**
* Writes the <code>double</code> value of the specified
* <code>Double</code> object to the specified data output.
*
* <p>This implementation calls the writeDouble method of the data output
* with the <code>double</code> value of the object.</p>
*
* @param dataOutput the stream to write the <code>double</code> value of
* the specified <code>Double</code> object to.
* @param object the <code>Double</code> object that <code>double</code>
* value should be written to the data output.
* @throws IOException includes any I/O exceptions that may occur.
*/
@Override
public void write(DataOutput dataOutput, Double object) throws IOException {
dataOutput.writeDouble(object);
}
/**
* Writes the specified <code>double</code> value to the specified data
* output.
*
* <p>This implementation calls the write method with a <code>Double</code>
* object wrapping the specified <code>double</code> value.</p>
*
* @param dataOutput the stream to write the specified <code>double</code>
* value to.
* @param d the <code>double</code> value that should be written to the
* data output.
* @throws IOException includes any I/O exceptions that may occur.
*/
public void writeDouble(DataOutput dataOutput, double d) throws IOException {
write(dataOutput, d);
}
}