Top Description Methods
java.io

public Interface DataOutput

Known Direct Subinterfaces
java.io.ObjectOutput
Known Direct Implementers
java.io.DataOutputStream, java.io.ObjectOutputStream.BlockDataOutputStream, java.io.RandomAccessFile
The DataOutput interface provides for converting data from any of the Java primitive types to a series of bytes and writing these bytes to a binary stream. There is also a facility for converting a String into modified UTF-8 format and writing the resulting series of bytes.

For all the methods in this interface that write bytes, it is generally true that if a byte cannot be written for any reason, an IOException is thrown.

Author
Frank Yellin
Since
1.0
See Also
java.io.DataInput, java.io.DataOutputStream

Method Summary

Modifier and TypeMethod and Description
public void
write(int
the byte to be written.
b)

Writes to the output stream the eight low-order bits of the argument b.

public void
write(byte[]
the data.
b)

Writes to the output stream all the bytes in array b.

public void
write(byte[]
the data.
b, int
the start offset in the data.
off, int
the number of bytes to write.
len)

Writes len bytes from array b, in order, to the output stream.

public void
writeBoolean(boolean
the boolean to be written.
v)

Writes a boolean value to this output stream.

public void
writeByte(int
the byte value to be written.
v)

Writes to the output stream the eight low-order bits of the argument v.

public void
writeBytes(String
the string of bytes to be written.
s)

Writes a string to the output stream.

public void
writeChar(int
the char value to be written.
v)

Writes a char value, which is comprised of two bytes, to the output stream.

public void
writeChars(String
the string value to be written.
s)

Writes every character in the string s, to the output stream, in order, two bytes per character.

public void
writeDouble(double
the double value to be written.
v)

Writes a double value, which is comprised of eight bytes, to the output stream.

public void
writeFloat(float
the float value to be written.
v)

Writes a float value, which is comprised of four bytes, to the output stream.

public void
writeInt(int
the int value to be written.
v)

Writes an int value, which is comprised of four bytes, to the output stream.

public void
writeLong(long
the long value to be written.
v)

Writes a long value, which is comprised of eight bytes, to the output stream.

public void
writeShort(int
the short value to be written.
v)

Writes two bytes to the output stream to represent the value of the argument.

public void
writeUTF(String
the string value to be written.
s)

Writes two bytes of length information to the output stream, followed by the modified UTF-8 representation of every character in the string s.

Method Detail

writeback to summary
public void write(int b) throws IOException

Writes to the output stream the eight low-order bits of the argument b. The 24 high-order bits of b are ignored.

Parameters
b:int

the byte to be written.

Exceptions
IOException:
if an I/O error occurs.
writeback to summary
public void write(byte[] b) throws IOException

Writes to the output stream all the bytes in array b. If b is null, a NullPointerException is thrown. If b.length is zero, then no bytes are written. Otherwise, the byte b[0] is written first, then b[1], and so on; the last byte written is b[b.length-1].

Parameters
b:byte[]

the data.

Exceptions
IOException:
if an I/O error occurs.
writeback to summary
public void write(byte[] b, int off, int len) throws IOException

Writes len bytes from array b, in order, to the output stream. If b is null, a NullPointerException is thrown. If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown. If len is zero, then no bytes are written. Otherwise, the byte b[off] is written first, then b[off+1], and so on; the last byte written is b[off+len-1].

Parameters
b:byte[]

the data.

off:int

the start offset in the data.

len:int

the number of bytes to write.

Exceptions
IOException:
if an I/O error occurs.
IndexOutOfBoundsException:
If off is negative, len is negative, or len is greater than b.length - off
writeBooleanback to summary
public void writeBoolean(boolean v) throws IOException

Writes a boolean value to this output stream. If the argument v is true, the value (byte)1 is written; if v is false, the value (byte)0 is written. The byte written by this method may be read by the readBoolean method of interface DataInput, which will then return a boolean equal to v.

Parameters
v:boolean

the boolean to be written.

Exceptions
IOException:
if an I/O error occurs.
writeByteback to summary
public void writeByte(int v) throws IOException

Writes to the output stream the eight low-order bits of the argument v. The 24 high-order bits of v are ignored. (This means that writeByte does exactly the same thing as write for an integer argument.) The byte written by this method may be read by the readByte method of interface DataInput, which will then return a byte equal to (byte)v.

Parameters
v:int

the byte value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeBytesback to summary
public void writeBytes(String s) throws IOException

Writes a string to the output stream. For every character in the string s, taken in order, one byte is written to the output stream. If s is null, a NullPointerException is thrown.

If s.length is zero, then no bytes are written. Otherwise, the character s[0] is written first, then s[1], and so on; the last character written is s[s.length-1]. For each character, one byte is written, the low-order byte, in exactly the manner of the writeByte method . The high-order eight bits of each character in the string are ignored.

Parameters
s:String

the string of bytes to be written.

Exceptions
IOException:
if an I/O error occurs.
writeCharback to summary
public void writeChar(int v) throws IOException

Writes a char value, which is comprised of two bytes, to the output stream. The byte values to be written, in the order shown, are: 

(byte)(0xff & (v >> 8))
(byte)(0xff & v)

The bytes written by this method may be read by the readChar method of interface DataInput, which will then return a char equal to (char)v.

Parameters
v:int

the char value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeCharsback to summary
public void writeChars(String s) throws IOException

Writes every character in the string s, to the output stream, in order, two bytes per character. If s is null, a NullPointerException is thrown. If s.length is zero, then no characters are written. Otherwise, the character s[0] is written first, then s[1], and so on; the last character written is s[s.length-1]. For each character, two bytes are actually written, high-order byte first, in exactly the manner of the writeChar method.

Parameters
s:String

the string value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeDoubleback to summary
public void writeDouble(double v) throws IOException

Writes a double value, which is comprised of eight bytes, to the output stream. It does this as if it first converts this double value to a long in exactly the manner of the Double.doubleToLongBits method and then writes the long value in exactly the manner of the writeLong method. The bytes written by this method may be read by the readDouble method of interface DataInput, which will then return a double equal to v.

Parameters
v:double

the double value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeFloatback to summary
public void writeFloat(float v) throws IOException

Writes a float value, which is comprised of four bytes, to the output stream. It does this as if it first converts this float value to an int in exactly the manner of the Float.floatToIntBits method and then writes the int value in exactly the manner of the writeInt method. The bytes written by this method may be read by the readFloat method of interface DataInput, which will then return a float equal to v.

Parameters
v:float

the float value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeIntback to summary
public void writeInt(int v) throws IOException

Writes an int value, which is comprised of four bytes, to the output stream. The byte values to be written, in the order shown, are: 

(byte)(0xff & (v >> 24))
(byte)(0xff & (v >> 16))
(byte)(0xff & (v >>  8))
(byte)(0xff & v)

The bytes written by this method may be read by the readInt method of interface DataInput, which will then return an int equal to v.

Parameters
v:int

the int value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeLongback to summary
public void writeLong(long v) throws IOException

Writes a long value, which is comprised of eight bytes, to the output stream. The byte values to be written, in the order shown, are: 

(byte)(0xff & (v >> 56))
(byte)(0xff & (v >> 48))
(byte)(0xff & (v >> 40))
(byte)(0xff & (v >> 32))
(byte)(0xff & (v >> 24))
(byte)(0xff & (v >> 16))
(byte)(0xff & (v >>  8))
(byte)(0xff & v)

The bytes written by this method may be read by the readLong method of interface DataInput, which will then return a long equal to v.

Parameters
v:long

the long value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeShortback to summary
public void writeShort(int v) throws IOException

Writes two bytes to the output stream to represent the value of the argument. The byte values to be written, in the order shown, are: 

(byte)(0xff & (v >> 8))
(byte)(0xff & v)

The bytes written by this method may be read by the readShort method of interface DataInput, which will then return a short equal to (short)v.

Parameters
v:int

the short value to be written.

Exceptions
IOException:
if an I/O error occurs.
writeUTFback to summary
public void writeUTF(String s) throws IOException

Writes two bytes of length information to the output stream, followed by the modified UTF-8 representation of every character in the string s. If s is null, a NullPointerException is thrown. Each character in the string s is converted to a group of one, two, or three bytes, depending on the value of the character.

If a character c is in the range \u0001 through \u007f, it is represented by one byte: 

(byte)c

If a character c is \u0000 or is in the range \u0080 through \u07ff, then it is represented by two bytes, to be written in the order shown: 

(byte)(0xc0 | (0x1f & (c >> 6)))
(byte)(0x80 | (0x3f & c))

If a character c is in the range \u0800 through uffff, then it is represented by three bytes, to be written in the order shown: 

(byte)(0xe0 | (0x0f & (c >> 12)))
(byte)(0x80 | (0x3f & (c >>  6)))
(byte)(0x80 | (0x3f & c))

First, the total number of bytes needed to represent all the characters of s is calculated. If this number is larger than 65535, then a UTFDataFormatException is thrown. Otherwise, this length is written to the output stream in exactly the manner of the writeShort method; after this, the one-, two-, or three-byte representation of each character in the string s is written.

The bytes written by this method may be read by the readUTF method of interface DataInput, which will then return a String equal to s.

Parameters
s:String

the string value to be written.

Exceptions
IOException:
if an I/O error occurs.