DataInputStream

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## 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:

| Bit Values
Byte 1 | 0 | bits 6-0

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

| Bit Values
Byte 1 | 1 | 1 | 0 | bits 10-6
Byte 2 | 1 | 0 | bits 5-0

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

| Bit Values
Byte 1 | 1 | 1 | 1 | 0 | bits 15-12
Byte 2 | 1 | 0 | bits 11-6
Byte 3 | 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
Version:
  1.52 10/17/00
Author:
  Arthur van Hoff
See Also:
  `DataOutputStream`

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
`equals, 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 Java modified UTF-8 encoding of a Unicode string.
  See Also:
    `readUnsignedShort()`

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