DataInputStream (Java Card API, Connected Edition)
Date: 2009-12-11

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## java.io
Class DataInputStream

    java.lang.Object
      java.io.InputStream
          java.io.DataInputStream

All Implemented Interfaces:
  DataInput

    @TransactionType(value=NOT_SUPPORTED)
    public class DataInputStream

extends InputStream
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.

Since:
  JDK1.0, CLDC 1.0, Java Card 3.0
See Also:
  `DataOutputStream`

Field Summary
`protected InputStream` | `in` The input stream.

Constructor Summary
`DataInputStream(InputStream in)` Creates a `DataInputStream` and saves its argument, the input stream `in`, for later use.

Method Summary
`int` | `available()` Returns the number of bytes that can be read from this input stream without blocking.
`void` | `close()` Closes this input stream and releases any system resources associated with the stream.
`void` | `mark(int readlimit)` Marks the current position in this input stream.
`boolean` | `markSupported()` Tests if this input stream supports the `mark` and `reset` methods.
`int` | `read()` Reads the next byte of data from this input stream.
`int` | `read(byte[] b)` See the general contract of the `read` method of `DataInput`.
`int` | `read(byte[] b, int off, int len)` Reads up to `len` bytes of data from this 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`.
`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`.
`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`.
`void` | `reset()` Repositions this stream to the position at the time the `mark` method was last called on this input stream.
`long` | `skip(long n)` Skips over and discards `n` bytes of data from the input stream.
`int` | `skipBytes(int n)` See the general contract of the `skipBytes` method of `DataInput`.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### in

    protected InputStream in

  The input stream.

Constructor Detail

### DataInputStream

    public DataInputStream(InputStream in)

  Creates a `DataInputStream` and saves its argument, the input stream `in`, for later use.

  Parameters:
    `in` - the input stream.

Method Detail

### read

    public int read()
             throws IOException

  Reads the next byte of data from this input stream. The value byte is returned as an `int` in the range `0` to `255`. If no byte is available because the end of the stream has been reached, the value `-1` is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

  This method simply performs `in.read()` and returns the result.

  Specified by:
    `read` in class `InputStream`
  Returns:
    the next byte of data, or `-1` if the end of the stream is reached.
  Throws:
    `IOException` - if an I/O error occurs.

### read

    public final int read(byte[] b)
                   throws IOException

  See the general contract of the `read` method of `DataInput`.

  Bytes for this operation are read from the contained input stream.

  Overrides:
    `read` in class `InputStream`
  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:
    `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 this input stream into an array of bytes. This method blocks until some input is available.

  This method simply performs `in.read(b, off, len)` and returns the result.

  Overrides:
    `read` in class `InputStream`
  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:
    `InputStream.read()`

### 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.

### 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.

### 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.

### 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.

### 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.

### 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.

### 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.

### 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.

### 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.

### 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.

### 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.
  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()`

### skip

    public long skip(long n)
              throws IOException

  Skips over and discards `n` bytes of data from the input stream. The `skip` method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly `0`. The actual number of bytes skipped is returned.

  This method simply performs `in.skip(n)`.

  Overrides:
    `skip` in class `InputStream`
  Parameters:
    `n` - the number of bytes to be skipped.
  Returns:
    the actual number of bytes skipped.
  Throws:
    `IOException` - if an I/O error occurs.

### available

    public int available()
                  throws IOException

  Returns the number of bytes that can be read from this input stream without blocking.

  This method simply performs `in.available()` and returns the result.

  Overrides:
    `available` in class `InputStream`
  Returns:
    the number of bytes that can be read from the input stream without blocking.
  Throws:
    `IOException` - if an I/O error occurs.

### close

    public void close()
               throws IOException

  Closes this input stream and releases any system resources associated with the stream. This method simply performs `in.close()`.

  Overrides:
    `close` in class `InputStream`
  Throws:
    `IOException` - if an I/O error occurs.

### mark

    public void mark(int readlimit)

  Marks the current position in this input stream. A subsequent call to the `reset` method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

  The `readlimit` argument tells this input stream to allow that many bytes to be read before the mark position gets invalidated.

  This method simply performs `in.mark(readlimit)`.

  Overrides:
    `mark` in class `InputStream`
  Parameters:
    `readlimit` - the maximum limit of bytes that can be read before the mark position becomes invalid.
  See Also:
    `InputStream.reset()`

### reset

    public void reset()
               throws IOException

  Repositions this stream to the position at the time the `mark` method was last called on this input stream.

  This method simply performs `in.reset()`.

  Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.

  Overrides:
    `reset` in class `InputStream`
  Throws:
    `IOException` - if the stream has not been marked or if the mark has been invalidated.
  See Also:
    `InputStream.mark(int)`, `IOException`

### markSupported

    public boolean markSupported()

  Tests if this input stream supports the `mark` and `reset` methods. This method simply performs `in.markSupported()`.

  Overrides:
    `markSupported` in class `InputStream`
  Returns:
    `true` if this stream type supports the `mark` and `reset` method; `false` otherwise.
  See Also:
    `InputStream.mark(int)`, `InputStream.reset()`

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