Java™ Platform
Standard Ed. 6

java.io
Class DataInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by java.io.FilterInputStream
          extended by java.io.DataInputStream
All Implemented Interfaces:
Closeable, 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.

DataInputStream is not necessarily safe for multithreaded access. Thread safety is optional and is the responsibility of users of methods in this class.

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 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.

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 the first byte cannot be read for any reason other than end of file, the stream has been closed and the underlying input stream does not support reading after close, or another 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 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.

Overrides:
read in class FilterInputStream
Parameters:
b - the buffer into which the data is read.
off - the start offset in the destination array b
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:
NullPointerException - If b is null.
IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off
IOException - if the first byte cannot be read for any reason other than end of file, the stream has been closed and the underlying input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 the contained input stream does not support seek, or the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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, interpreted as a char.
Throws:
EOFException - if this input stream reaches the end before reading two bytes.
IOException - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another 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 - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.
See Also:
readLong(), Double.longBitsToDouble(long)

readLine

@Deprecated
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 - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.
UTFDataFormatException - if the bytes do not represent a valid modified 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 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 - the stream has been closed and the contained input stream does not support reading after close, or another I/O error occurs.
UTFDataFormatException - if the bytes do not represent a valid modified UTF-8 encoding of a Unicode string.
See Also:
readUnsignedShort()

Java™ Platform
Standard Ed. 6

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