java.io
Class DataOutputStream

java.lang.Object
  java.io.OutputStream
      java.io.FilterOutputStream
          java.io.DataOutputStream

All Implemented Interfaces:

DataOutput

public class DataOutputStream

extends FilterOutputStream

implements DataOutput

A data output stream lets an application write primitive Java data types to an output stream in a portable way. An application can then use a data input stream to read the data back in.

Since:

JDK1.0

Author:

unascribed

See Also:

DataInputStream

Field Summary

private byte[]	writeBuffer
protected int	written The number of bytes written to the data output stream so far.

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

DataOutputStream(OutputStream out)
Creates a new data output stream to write data to the specified underlying output stream.

Method Summary

void	flush() Flushes this data output stream.
private void	incCount(int value) Increases the written counter by the specified value until it reaches Integer.MAX_VALUE.
int	size() Returns the current value of the counter written, the number of bytes written to this data output stream so far.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to the underlying output stream.
void	write(int b) Writes the specified byte (the low eight bits of the argument b) to the underlying output stream.
void	writeBoolean(boolean v) Writes a boolean to the underlying output stream as a 1-byte value.
void	writeByte(int v) Writes out a byte to the underlying output stream as a 1-byte value.
void	writeBytes(String s) Writes out the string to the underlying output stream as a sequence of bytes.
void	writeChar(int v) Writes a char to the underlying output stream as a 2-byte value, high byte first.
void	writeChars(String s) Writes a string to the underlying output stream as a sequence of characters.
void	writeDouble(double v) Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first.
void	writeFloat(float v) Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first.
void	writeInt(int v) Writes an int to the underlying output stream as four bytes, high byte first.
void	writeLong(long v) Writes a long to the underlying output stream as eight bytes, high byte first.
void	writeShort(int v) Writes a short to the underlying output stream as two bytes, high byte first.
void	writeUTF(String str) Writes a string to the underlying output stream using Java modified UTF-8 encoding in a machine-independent manner.
(package private) static int	writeUTF(String str, DataOutput out) Writes a string to the specified DataOutput using Java modified UTF-8 encoding in a machine-independent manner.

Methods inherited from class java.io.FilterOutputStream

close, write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.io.DataOutput

write

Field Detail

written

protected int written

The number of bytes written to the data output stream so far. If this counter overflows, it will be wrapped to Integer.MAX_VALUE.

writeBuffer

private byte[] writeBuffer

Constructor Detail

DataOutputStream

public DataOutputStream(OutputStream out)

Creates a new data output stream to write data to the specified underlying output stream. The counter written is set to zero.

Parameters:

out - the underlying output stream, to be saved for later use.

See Also:

FilterOutputStream.out

Method Detail

incCount

private void incCount(int value)

Increases the written counter by the specified value until it reaches Integer.MAX_VALUE.

write

public void write(int b)
           throws IOException

Writes the specified byte (the low eight bits of the argument b) to the underlying output stream. If no exception is thrown, the counter written is incremented by 1.

Implements the write method of OutputStream.

Specified by:

write in interface DataOutput

Overrides:

write in class FilterOutputStream

Parameters:

b - the byte to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException

Writes len bytes from the specified byte array starting at offset off to the underlying output stream. If no exception is thrown, the counter written is incremented by len.

Specified by:

write in interface DataOutput

Overrides:

write in class FilterOutputStream

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

flush

public void flush()
           throws IOException

Flushes this data output stream. This forces any buffered output bytes to be written out to the stream.

The flush method of DataOuputStream calls the flush method of its underlying output stream.

Overrides:

flush in class FilterOutputStream

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out, OutputStream.flush()

writeBoolean

public final void writeBoolean(boolean v)
                        throws IOException

Writes a boolean to the underlying output stream as a 1-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0. If no exception is thrown, the counter written is incremented by 1.

Specified by:

writeBoolean in interface DataOutput

Parameters:

v - a boolean value to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeByte

public final void writeByte(int v)
                     throws IOException

Writes out a byte to the underlying output stream as a 1-byte value. If no exception is thrown, the counter written is incremented by 1.

Specified by:

writeByte in interface DataOutput

Parameters:

v - a byte value to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeShort

public final void writeShort(int v)
                      throws IOException

Writes a short to the underlying output stream as two bytes, high byte first. If no exception is thrown, the counter written is incremented by 2.

Specified by:

writeShort in interface DataOutput

Parameters:

v - a short to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeChar

public final void writeChar(int v)
                     throws IOException

Writes a char to the underlying output stream as a 2-byte value, high byte first. If no exception is thrown, the counter written is incremented by 2.

Specified by:

writeChar in interface DataOutput

Parameters:

v - a char value to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeInt

public final void writeInt(int v)
                    throws IOException

Writes an int to the underlying output stream as four bytes, high byte first. If no exception is thrown, the counter written is incremented by 4.

Specified by:

writeInt in interface DataOutput

Parameters:

v - an int to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeLong

public final void writeLong(long v)
                     throws IOException

Writes a long to the underlying output stream as eight bytes, high byte first. In no exception is thrown, the counter written is incremented by 8.

Specified by:

writeLong in interface DataOutput

Parameters:

v - a long to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeFloat

public final void writeFloat(float v)
                      throws IOException

Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first. If no exception is thrown, the counter written is incremented by 4.

Specified by:

writeFloat in interface DataOutput

Parameters:

v - a float value to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out, Float.floatToIntBits(float)

writeDouble

public final void writeDouble(double v)
                       throws IOException

Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first. If no exception is thrown, the counter written is incremented by 8.

Specified by:

writeDouble in interface DataOutput

Parameters:

v - a double value to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out, Double.doubleToLongBits(double)

writeBytes

public final void writeBytes(String s)
                      throws IOException

Writes out the string to the underlying output stream as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits. If no exception is thrown, the counter written is incremented by the length of s.

Specified by:

writeBytes in interface DataOutput

Parameters:

s - a string of bytes to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

FilterOutputStream.out

writeChars

public final void writeChars(String s)
                      throws IOException

Writes a string to the underlying output stream as a sequence of characters. Each character is written to the data output stream as if by the writeChar method. If no exception is thrown, the counter written is incremented by twice the length of s.

Specified by:

writeChars in interface DataOutput

Parameters:

s - a String value to be written.

Throws:

IOException - if an I/O error occurs.

See Also:

writeChar(int), FilterOutputStream.out

writeUTF

public final void writeUTF(String str)
                    throws IOException

Writes a string to the underlying output stream using Java modified UTF-8 encoding in a machine-independent manner.

First, two bytes are written to the output stream as if by the writeShort method giving the number of bytes to follow. This value is the number of bytes actually written out, not the length of the string. Following the length, each character of the string is output, in sequence, using the modified UTF-8 encoding for the character. If no exception is thrown, the counter written is incremented by the total number of bytes written to the output stream. This will be at least two plus the length of str, and at most two plus thrice the length of str.

Specified by:

writeUTF in interface DataOutput

Parameters:

str - a string to be written.

Throws:

IOException - if an I/O error occurs.

writeUTF

static int writeUTF(String str,
                    DataOutput out)
             throws IOException

Writes a string to the specified DataOutput using Java modified UTF-8 encoding in a machine-independent manner.

First, two bytes are written to out as if by the writeShort method giving the number of bytes to follow. This value is the number of bytes actually written out, not the length of the string. Following the length, each character of the string is output, in sequence, using the modified UTF-8 encoding for the character. If no exception is thrown, the counter written is incremented by the total number of bytes written to the output stream. This will be at least two plus the length of str, and at most two plus thrice the length of str.

Parameters:

str - a string to be written.

out - destination to write to

Returns:

The number of bytes written out.

Throws:

IOException - if an I/O error occurs.

size

public final int size()

Returns the current value of the counter written, the number of bytes written to this data output stream so far. If the counter overflows, it will be wrapped to Integer.MAX_VALUE.

Returns:

the value of the written field.

See Also:

written