java.io

Class DataOutputStream

Implemented Interfaces:
AutoCloseable, Closeable, DataOutput, Flushable

public class DataOutputStream
extends FilterOutputStream
implements DataOutput

This class provides a mechanism for writing primitive Java datatypes to an OutputStream in a portable way. Data written to a stream using this class can be read back in using the DataInputStream class on any platform.
See Also:
DataInputStream

Field Summary

protected int
written
This is the total number of bytes that have been written to the stream by this object instance.

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

DataOutputStream(OutputStream out)
This method initializes an instance of DataOutputStream to write its data to the specified underlying OutputStream

Method Summary

void
flush()
This method flushes any unwritten bytes to the underlying stream.
int
size()
This method returns the total number of bytes that have been written to the underlying output stream so far.
void
write(byte[] buf, int offset, int len)
This method writes len bytes from the specified byte array buf starting at position offset into the buffer to the underlying output stream.
void
write(int value)
This method writes the specified byte (passed as an int) to the underlying output stream.
void
writeBoolean(boolean value)
This method writes a Java boolean value to an output stream.
void
writeByte(int value)
This method writes a Java byte value to an output stream.
void
writeBytes(String value)
This method writes all the bytes in a String out to the stream.
void
writeChar(int value)
This method writes a Java char value to an output stream.
void
writeChars(String value)
This method writes all the characters of a String to an output stream as an array of char's.
void
writeDouble(double value)
This method writes a Java double value to the stream.
void
writeFloat(float value)
This method writes a Java float value to the stream.
void
writeInt(int value)
This method writes a Java int value to an output stream.
void
writeLong(long value)
This method writes a Java long value to an output stream.
void
writeShort(int value)
This method writes a Java short value to an output stream.
void
writeUTF(String value)
This method writes a Java String to the stream in a modified UTF-8 format.

Methods inherited from class java.io.FilterOutputStream

close, flush, write, write, write

Methods inherited from class java.io.OutputStream

close, flush, write, write, write

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

written

protected int written
This is the total number of bytes that have been written to the stream by this object instance.

Constructor Details

DataOutputStream

public DataOutputStream(OutputStream out)
This method initializes an instance of DataOutputStream to write its data to the specified underlying OutputStream
Parameters:
out - The subordinate OutputStream to which this object will write

Method Details

flush

public void flush()
            throws IOException
This method flushes any unwritten bytes to the underlying stream.
Specified by:
flush in interface Flushable
Overrides:
flush in interface FilterOutputStream
Throws:
IOException - If an error occurs.

size

public final int size()
This method returns the total number of bytes that have been written to the underlying output stream so far. This is the value of the written instance variable
Returns:
The number of bytes written to the stream.

write

public void write(byte[] buf,
                  int offset,
                  int len)
            throws IOException
This method writes len bytes from the specified byte array buf starting at position offset into the buffer to the underlying output stream.
Specified by:
write in interface DataOutput
Overrides:
write in interface FilterOutputStream
Parameters:
buf - The byte array to write from.
offset - The index into the byte array to start writing from.
len - The number of bytes to write.
Throws:
IOException - If an error occurs.

write

public void write(int value)
            throws IOException
This method writes the specified byte (passed as an int) to the underlying output stream.
Specified by:
write in interface DataOutput
Overrides:
write in interface FilterOutputStream
Parameters:
value - The byte to write, passed as an int.
Throws:
IOException - If an error occurs.

writeBoolean

public final void writeBoolean(boolean value)
            throws IOException
This method writes a Java boolean value to an output stream. If value is true, a byte with the value of 1 will be written, otherwise a byte with the value of 0 will be written. The value written can be read using the readBoolean method in DataInput.
Specified by:
writeBoolean in interface DataOutput
Parameters:
value - The boolean value to write to the stream
Throws:
IOException - If an error occurs

writeByte

public final void writeByte(int value)
            throws IOException
This method writes a Java byte value to an output stream. The byte to be written will be in the lowest 8 bits of the int value passed. The value written can be read using the readByte or readUnsignedByte methods in DataInput.
Specified by:
writeByte in interface DataOutput
Parameters:
value - The byte to write to the stream, passed as the low eight bits of an int.
Throws:
IOException - If an error occurs

writeBytes

public final void writeBytes(String value)
            throws IOException
This method writes all the bytes in a String out to the stream. One byte is written for each character in the String. The high eight bits of each character are discarded, thus this method is inappropriate for completely representing Unicode characters.
Specified by:
writeBytes in interface DataOutput
Parameters:
value - The String to write to the stream
Throws:
IOException - If an error occurs

writeChar

public final void writeChar(int value)
            throws IOException
This method writes a Java char value to an output stream. The char to be written will be in the lowest 16 bits of the int value passed. These bytes will be written "big endian". That is, with the high byte written first in the following manner:

byte0 = (byte)((value & 0xFF00) >> 8);
byte1 = (byte)(value & 0x00FF);

The value written can be read using the readChar method in DataInput.

Specified by:
writeChar in interface DataOutput
Parameters:
value - The char value to write, passed as an int.
Throws:
IOException - If an error occurs

writeChars

public final void writeChars(String value)
            throws IOException
This method writes all the characters of a String to an output stream as an array of char's. Each character is written using the method specified in the writeChar method.
Specified by:
writeChars in interface DataOutput
Parameters:
value - The String to write to the stream
Throws:
IOException - If an error occurs
See Also:
writeChar(char)

writeDouble

public final void writeDouble(double value)
            throws IOException
This method writes a Java double value to the stream. This value is written by first calling the method Double.doubleToLongBits to retrieve an long representing the floating point number, then writing this long value to the stream exactly the same as the writeLong() method does. The value written can be read using the readDouble method in DataInput.
Specified by:
writeDouble in interface DataOutput
Parameters:
value - The double value to write to the stream
Throws:
IOException - If an error occurs

writeFloat

public final void writeFloat(float value)
            throws IOException
This method writes a Java float value to the stream. This value is written by first calling the method Float.floatToIntBits to retrieve an int representing the floating point number, then writing this int value to the stream exactly the same as the writeInt() method does. The value written can be read using the readFloat method in DataInput.
Specified by:
writeFloat in interface DataOutput
Parameters:
value - The float value to write to the stream
Throws:
IOException - If an error occurs

writeInt

public final void writeInt(int value)
            throws IOException
This method writes a Java int value to an output stream. The 4 bytes of the passed value will be written "big endian". That is, with the high byte written first in the following manner:

byte0 = (byte)((value & 0xFF000000) >> 24);
byte1 = (byte)((value & 0x00FF0000) >> 16);
byte2 = (byte)((value & 0x0000FF00) >> 8);
byte3 = (byte)(value & 0x000000FF);

The value written can be read using the readInt method in DataInput.

Specified by:
writeInt in interface DataOutput
Parameters:
value - The int value to write to the stream
Throws:
IOException - If an error occurs

writeLong

public final void writeLong(long value)
            throws IOException
This method writes a Java long value to an output stream. The 8 bytes of the passed value will be written "big endian". That is, with the high byte written first in the following manner:

byte0 = (byte)((value & 0xFF00000000000000L) >> 56);
byte1 = (byte)((value & 0x00FF000000000000L) >> 48);
byte2 = (byte)((value & 0x0000FF0000000000L) >> 40);
byte3 = (byte)((value & 0x000000FF00000000L) >> 32);
byte4 = (byte)((value & 0x00000000FF000000L) >> 24);
byte5 = (byte)((value & 0x0000000000FF0000L) >> 16);
byte6 = (byte)((value & 0x000000000000FF00L) >> 8);
byte7 = (byte)(value & 0x00000000000000FFL);

The value written can be read using the readLong method in DataInput.

Specified by:
writeLong in interface DataOutput
Parameters:
value - The long value to write to the stream
Throws:
IOException - If an error occurs

writeShort

public final void writeShort(int value)
            throws IOException
This method writes a Java short value to an output stream. The char to be written will be in the lowest 16 bits of the int value passed. These bytes will be written "big endian". That is, with the high byte written first in the following manner:

byte0 = (byte)((value & 0xFF00) >> 8);
byte1 = (byte)(value & 0x00FF);

The value written can be read using the readShort and readUnsignedShort methods in DataInput.

Specified by:
writeShort in interface DataOutput
Parameters:
value - The short value to write to the stream, passed as an int.
Throws:
IOException - If an error occurs

writeUTF

public final void writeUTF(String value)
            throws IOException
This method writes a Java String to the stream in a modified UTF-8 format. First, two bytes are written to the stream indicating the number of bytes to follow. Note that this is the number of bytes in the encoded String not the String length. Next come the encoded characters. Each character in the String is encoded as either one, two or three bytes. For characters in the range of \u0001 to <\u007F>, one byte is used. The character value goes into bits 0-7 and bit eight is 0. For characters in the range of \u0080 to \u007FF, two bytes are used. Bits 6-10 of the character value are encoded bits 0-4 of the first byte, with the high bytes having a value of "110". Bits 0-5 of the character value are stored in bits 0-5 of the second byte, with the high bits set to "10". This type of encoding is also done for the null character \u0000. This eliminates any C style NUL character values in the output. All remaining characters are stored as three bytes. Bits 12-15 of the character value are stored in bits 0-3 of the first byte. The high bits of the first bytes are set to "1110". Bits 6-11 of the character value are stored in bits 0-5 of the second byte. The high bits of the second byte are set to "10". And bits 0-5 of the character value are stored in bits 0-5 of byte three, with the high bits of that byte set to "10". The value written can be read using the readUTF method in DataInput.
Specified by:
writeUTF in interface DataOutput
Parameters:
value - The String to write to the output in UTF format
Throws:
IOException - If an error occurs

DataOutputStream.java -- Writes primitive Java datatypes to streams Copyright (C) 1998, 2001, 2003, 2005, 2008 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath 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 General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.