DataInputStream (Java 2 Platform SE v1.4.1)

java.io
Class DataInputStream
java.lang.Object
  |
  +--java.io.InputStream
        |
        +--java.io.FilterInputStream
              |
              +--java.io.DataInputStream
All Implemented Interfaces:
DataInput

public class DataInputStream
extends FilterInputStream
implements DataInput

A data input stream lets an application read primitive Java data types from an underlying input stream in a machine-independent way. An application uses a data output stream to write data that can later be read by a data input stream.
Data input streams and data output streams represent Unicode strings in a format that is a slight modification of UTF-8. (For more information, see X/Open Company Ltd., "File System Safe UCS Transformation Format (FSS_UTF)", X/Open Preliminary Specification, Document Number: P316. This information also appears in ISO/IEC 10646, Annex P.) Note that in the following tables, the most significant bit appears in the far left-hand column.
All characters in the range '\u0001' to '\u007F' are represented by a single byte:

0 bits 6-0

The null character '\u0000' and characters in the range '\u0080' to '\u07FF' are represented by a pair of bytes:

1 1 0 bits 10-6

1 0 bits 5-0

Characters in the range '\u0800' to '\uFFFF' are represented by three bytes:

1 1 1 0 bits 15-12

1 0 bits 11-6

1 0 bits 5-0

The two differences between this format and the "standard" UTF-8 format are the following:

The null byte '\u0000' is encoded in 2-byte format rather than 1-byte, so that the encoded strings never have embedded nulls.
Only the 1-byte, 2-byte, and 3-byte formats are used.

Since:

JDK1.0

See Also:
DataOutputStream
Field Summary

Fields inherited from class java.io.FilterInputStream
in

Constructor Summary
DataInputStream(InputStream in)
Creates a DataInputStream that uses the specified underlying InputStream.
Method Summary
int read(byte[] b)
    Reads some number of bytes from the contained input stream and stores them into the buffer array b.
int read(byte[] b, int off, int len)
    Reads up to len bytes of data from the contained input stream into an array of bytes.
boolean readBoolean()
    See the general contract of the readBoolean method of DataInput.
byte readByte()
    See the general contract of the readByte method of DataInput.
char readChar()
    See the general contract of the readChar method of DataInput.
double readDouble()
    See the general contract of the readDouble method of DataInput.
float readFloat()
    See the general contract of the readFloat method of DataInput.
void readFully(byte[] b)
    See the general contract of the readFully method of DataInput.
void readFully(byte[] b, int off, int len)
    See the general contract of the readFully method of DataInput.
int readInt()
    See the general contract of the readInt method of DataInput.
String
readLine()
Deprecated. This method does not properly convert bytes to characters. As of JDK 1.1, the preferred way to read lines of text is via the BufferedReader.readLine() method. Programs that use the DataInputStream class to read lines can be converted to use the BufferedReader class by replacing code of the form:
     DataInputStream d = new DataInputStream(in);
 
with:
     BufferedReader d
          = new BufferedReader(new InputStreamReader(in));
 
long readLong()
    See the general contract of the readLong method of DataInput.
short readShort()
    See the general contract of the readShort method of DataInput.
int readUnsignedByte()
    See the general contract of the readUnsignedByte method of DataInput.
int readUnsignedShort()
    See the general contract of the readUnsignedShort method of DataInput.
String readUTF()
    See the general contract of the readUTF method of DataInput.
static String readUTF(DataInput in)
    Reads from the stream in a representation of a Unicode character string encoded in Java modified UTF-8 format; this string of characters is then returned as a String.
int skipBytes(int n)
    See the general contract of the skipBytes method of DataInput.
Methods inherited from class java.io.FilterInputStream
available, close, mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Constructor Detail

DataInputStream
public DataInputStream(InputStream in)
Creates a DataInputStream that uses the specified underlying InputStream.

Parameters:
in - the specified input stream

Method Detail

read
public final int read(byte[] b)
               throws IOException
Reads some number of bytes from the contained input stream and stores them into the buffer array b. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown.
If b is null, a NullPointerException is thrown. If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.
The first byte read is stored into element b[0], the next one into b[1], and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[k-1], leaving elements b[k] through b[b.length-1] unaffected.
If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.
The read(b) method has the same effect as:
 read(b, 0, b.length) 
 
Overrides:
read in class FilterInputStream

Parameters:
b - the buffer into which the data is read.
Returns:
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
Throws:
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in, InputStream.read(byte[], int, int)
read
public final int read(byte[] b,
                      int off,
                      int len)
               throws IOException
Reads up to len bytes of data from the contained input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read, possibly zero. The number of bytes actually read is returned as an integer.
This method blocks until input data is available, end of file is detected, or an exception is thrown.
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 read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.
The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.
In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.
If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

Overrides:
read in class FilterInputStream

Parameters:
b - the buffer into which the data is read.
off - the start offset of the data.
len - the maximum number of bytes read.
Returns:
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
Throws:
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in, InputStream.read(byte[], int, int)

readFully
public final void readFully(byte[] b)
                     throws IOException
See the general contract of the readFully method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readFully in interface DataInput

Parameters:
b - the buffer into which the data is read.
Throws:
EOFException - if this input stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readFully
public final void readFully(byte[] b,
                            int off,
                            int len)
                     throws IOException
See the general contract of the readFully method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readFully in interface DataInput

Parameters:
b - the buffer into which the data is read.
off - the start offset of the data.
len - the number of bytes to read.
Throws:
EOFException - if this input stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

skipBytes
public final int skipBytes(int n)
                    throws IOException
See the general contract of the skipBytes method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
skipBytes in interface DataInput

Parameters:
n - the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws:
IOException - if an I/O error occurs.

readBoolean
public final boolean readBoolean()
                          throws IOException
See the general contract of the readBoolean method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readBoolean in interface DataInput

Returns:
the boolean value read.
Throws:
EOFException - if this input stream has reached the end.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readByte
public final byte readByte()
                    throws IOException
See the general contract of the readByte method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readByte in interface DataInput

Returns:
the next byte of this input stream as a signed 8-bit byte.
Throws:
EOFException - if this input stream has reached the end.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readUnsignedByte
public final int readUnsignedByte()
                           throws IOException
See the general contract of the readUnsignedByte method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readUnsignedByte in interface DataInput

Returns:
the next byte of this input stream, interpreted as an unsigned 8-bit number.
Throws:
EOFException - if this input stream has reached the end.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readShort
public final short readShort()
                      throws IOException
See the general contract of the readShort method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readShort in interface DataInput

Returns:
the next two bytes of this input stream, interpreted as a signed 16-bit number.
Throws:
EOFException - if this input stream reaches the end before reading two bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readUnsignedShort
public final int readUnsignedShort()
                            throws IOException
See the general contract of the readUnsignedShort method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readUnsignedShort in interface DataInput

Returns:
the next two bytes of this input stream, interpreted as an unsigned 16-bit integer.
Throws:
EOFException - if this input stream reaches the end before reading two bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readChar
public final char readChar()
                    throws IOException
See the general contract of the readChar method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readChar in interface DataInput

Returns:
the next two bytes of this input stream as a Unicode character.
Throws:
EOFException - if this input stream reaches the end before reading two bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readInt
public final int readInt()
                  throws IOException
See the general contract of the readInt method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readInt in interface DataInput

Returns:
the next four bytes of this input stream, interpreted as an int.
Throws:
EOFException - if this input stream reaches the end before reading four bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readLong
public final long readLong()
                    throws IOException
See the general contract of the readLong method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readLong in interface DataInput

Returns:
the next eight bytes of this input stream, interpreted as a long.
Throws:
EOFException - if this input stream reaches the end before reading eight bytes.
IOException - if an I/O error occurs.
See Also:
FilterInputStream.in

readFloat
public final float readFloat()
                      throws IOException
See the general contract of the readFloat method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readFloat in interface DataInput

Returns:
the next four bytes of this input stream, interpreted as a float.
Throws:
EOFException - if this input stream reaches the end before reading four bytes.
IOException - if an I/O error occurs.
See Also:
readInt(), Float.intBitsToFloat(int)

readDouble
public final double readDouble()
                        throws IOException
See the general contract of the readDouble method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readDouble in interface DataInput

Returns:
the next eight bytes of this input stream, interpreted as a double.
Throws:
EOFException - if this input stream reaches the end before reading eight bytes.
IOException - if an I/O error occurs.
See Also:
readLong(), Double.longBitsToDouble(long)

readLine
public final String readLine()
                      throws IOException
Deprecated. This method does not properly convert bytes to characters. As of JDK 1.1, the preferred way to read lines of text is via the BufferedReader.readLine() method. Programs that use the DataInputStream class to read lines can be converted to use the BufferedReader class by replacing code of the form:
     DataInputStream d = new DataInputStream(in);
 
with:
     BufferedReader d
          = new BufferedReader(new InputStreamReader(in));
 
See the general contract of the readLine method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readLine in interface DataInput

Returns:
the next line of text from this input stream.
Throws:
IOException - if an I/O error occurs.
See Also:
BufferedReader.readLine(), FilterInputStream.in
readUTF
public final String readUTF()
                     throws IOException
See the general contract of the readUTF method of DataInput.
Bytes for this operation are read from the contained input stream.

Specified by:
readUTF in interface DataInput

Returns:
a Unicode string.
Throws:
EOFException - if this input stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.
UTFDataFormatException - if the bytes do not represent a valid UTF-8 encoding of a string.
See Also:
readUTF(java.io.DataInput)

readUTF
public static final String readUTF(DataInput in)
                            throws IOException
Reads from the stream in a representation of a Unicode character string encoded in Java modified UTF-8 format; this string of characters is then returned as a String. The details of the modified UTF-8 representation are exactly the same as for the readUTF method of DataInput.

Parameters:
in - a data input stream.
Returns:
a Unicode string.
Throws:
EOFException - if the input stream reaches the end before all the bytes.
IOException - if an I/O error occurs.
UTFDataFormatException - if the bytes do not represent a valid UTF-8 encoding of a Unicode string.
See Also:
readUnsignedShort()

Method Summary
int	read(byte[] b) Reads some number of bytes from the contained input stream and stores them into the buffer array b.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from the contained input stream into an array of bytes.
boolean	readBoolean() See the general contract of the readBoolean method of DataInput.
byte	readByte() See the general contract of the readByte method of DataInput.
char	readChar() See the general contract of the readChar method of DataInput.
double	readDouble() See the general contract of the readDouble method of DataInput.
float	readFloat() See the general contract of the readFloat method of DataInput.
void	readFully(byte[] b) See the general contract of the readFully method of DataInput.
void	readFully(byte[] b, int off, int len) See the general contract of the readFully method of DataInput.
int	readInt() See the general contract of the readInt method of DataInput.
String	readLine() Deprecated. This method does not properly convert bytes to characters. As of JDK 1.1, the preferred way to read lines of text is via the BufferedReader.readLine() method. Programs that use the DataInputStream class to read lines can be converted to use the BufferedReader class by replacing code of the form: DataInputStream d = new DataInputStream(in); with: BufferedReader d = new BufferedReader(new InputStreamReader(in));
long	readLong() See the general contract of the readLong method of DataInput.
short	readShort() See the general contract of the readShort method of DataInput.
int	readUnsignedByte() See the general contract of the readUnsignedByte method of DataInput.
int	readUnsignedShort() See the general contract of the readUnsignedShort method of DataInput.
String	readUTF() See the general contract of the readUTF method of DataInput.
static String	readUTF(DataInput in) Reads from the stream in a representation of a Unicode character string encoded in Java modified UTF-8 format; this string of characters is then returned as a String.
int	skipBytes(int n) See the general contract of the skipBytes method of DataInput.

java.io Class DataInputStream

Field Summary

Constructor Summary

Method Summary

Constructor Detail

DataInputStream

Method Detail

read

read

readFully

readFully

skipBytes

readBoolean

readByte

readUnsignedByte

readShort

readUnsignedShort

readChar

readInt

readLong

readFloat

readDouble

readLine

readUTF

readUTF

java.io
Class DataInputStream