java.io

Interface DataOutput

All Known Implementing Classes:

DataOutputStream

public interface DataOutput

This interface is implemented by classes that can wrte data to streams from Java primitive types. This data can subsequently be read back by classes implementing the DataInput interface.

Author:

Aaron M. Renn (arenn@urbanophile.com), Tom Tromey (tromey@cygnus.com)

See Also:

DataInput

Method Summary

Modifier and Type	Method and Description
void	write(byte[] buf) This method writes the raw byte array passed in to the output stream.
void	write(byte[] buf, int offset, int len) This method writes raw bytes from the passed array buf starting offset bytes into the buffer.
void	write(int value) This method writes an 8-bit value (passed into the method as a Java int) to an 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.

Method Detail

write

void write(byte[] buf)
    throws IOException

This method writes the raw byte array passed in to the output stream.

Parameters:

buf - The byte array to write

Throws:

IOException - If an error occurs

write

void write(byte[] buf,
           int offset,
           int len)
    throws IOException

This method writes raw bytes from the passed array buf starting offset bytes into the buffer. The number of bytes written will be exactly len.

Parameters:

buf - The buffer from which to write the data

offset - The offset into the buffer to start writing data from

len - The number of bytes to write from the buffer to the output stream

Throws:

IOException - If any other error occurs

write

void write(int value)
    throws IOException

This method writes an 8-bit value (passed into the method as a Java int) to an output stream. The low 8 bits of the passed value are written.

Parameters:

value - The byte to write to the output stream

Throws:

IOException - If an error occurs

writeBoolean

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.

Parameters:

value - The boolean value to write

Throws:

IOException - If an error occurs

See Also:

DataInput.readBoolean()

writeByte

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.

Parameters:

value - The int value to write

Throws:

IOException - If an error occurs

See Also:

DataInput.readByte(), DataInput.readUnsignedByte()

writeBytes

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.

Parameters:

value - The String to write

Throws:

IOException - If an error occurs

writeChar

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.

Parameters:

value - The char value to write

Throws:

IOException - If an error occurs

See Also:

DataInput.readChar()

writeChars

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.

Parameters:

value - The String to write

Throws:

IOException - If an error occurs

See Also:

writeChar(int)

writeDouble

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.

Parameters:

value - The double value to write

Throws:

IOException - If any other error occurs

See Also:

writeLong(long), DataInput.readDouble(), Double.doubleToLongBits(double)

writeFloat

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.

Parameters:

value - The float value to write

Throws:

IOException - If an error occurs

See Also:

writeInt(int), DataInput.readFloat(), Float.floatToIntBits(float)

writeInt

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.

Parameters:

value - The int value to write

Throws:

IOException - If an error occurs

See Also:

DataInput.readInt()

writeLong

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.

Parameters:

value - The long value to write

Throws:

IOException - If an error occurs

See Also:

DataInput.readLong()

writeShort

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.

Parameters:

value - The int value to write as a 16-bit value

Throws:

IOException - If an error occurs

See Also:

DataInput.readShort(), DataInput.readUnsignedShort()

writeUTF

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. This is written in the form of a Java short value in the same manner used by the writeShort method. 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
to , one byte is used. The character value goes into bits 0-7 and bit eight is 0. For characters in the range of € to F, 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 . 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.

Parameters:

value - The String to write

Throws:

IOException - If an error occurs

See Also:

DataInput.readUTF()