Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Methods](https://developer.android.com/reference/java/io/DataInput#pubmethods)
# DataInput
`
public
interface
DataInput
`
`
`
|---|
| java.io.DataInput |
|---|
| Known indirect subclasses [DataInputStream](https://developer.android.com/reference/java/io/DataInputStream), [ObjectInput](https://developer.android.com/reference/java/io/ObjectInput), [ObjectInputStream](https://developer.android.com/reference/java/io/ObjectInputStream), [RandomAccessFile](https://developer.android.com/reference/java/io/RandomAccessFile) |---|---| | [DataInputStream](https://developer.android.com/reference/java/io/DataInputStream) | A data input stream lets an application read primitive Java data types from an underlying input stream in a machine-independent way. | | [ObjectInput](https://developer.android.com/reference/java/io/ObjectInput) | ObjectInput extends the DataInput interface to include the reading of objects. | | [ObjectInputStream](https://developer.android.com/reference/java/io/ObjectInputStream) | An ObjectInputStream deserializes primitive data and objects previously written using an ObjectOutputStream. | | [RandomAccessFile](https://developer.android.com/reference/java/io/RandomAccessFile) | Instances of this class support both reading and writing to a random access file. | |
*** ** * ** ***
The `DataInput` interface provides
for reading bytes from a binary stream and
reconstructing from them data in any of
the Java primitive types. There is also
a
facility for reconstructing a `String`
from data in
[modified UTF-8](https://developer.android.com/reference/java/io/DataInput#modified-utf-8)
format.
It is generally true of all the reading
routines in this interface that if end of
file is reached before the desired number
of bytes has been read, an `EOFException`
(which is a kind of `IOException`)
is thrown. If any byte cannot be read for
any reason other than end of file, an `IOException`
other than `EOFException` is
thrown. In particular, an `IOException`
may be thrown if the input stream has been
closed.
### Modified UTF-8
Implementations of the DataInput and DataOutput interfaces represent
Unicode strings in a format that is a slight modification of UTF-8.
(For information regarding the standard UTF-8 format, see section
*3.9 Unicode Encoding Forms* of *The Unicode Standard, Version 4.0*)
- Characters in the range `'\u0001'` to `'\u007F'` are represented by a single byte.
- The null character `'\u0000'` and characters in the range `'\u0080'` to `'\u07FF'` are represented by a pair of bytes.
- Characters in the range `'\u0800'` to `'\uFFFF'` are represented by three bytes.
| Value | Byte | Bit Values ||||||||
| Value | Byte | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| `\u0001` to `\u007F` | 1 | 0 | bits 6-0 |||||||
| `\u0000`, `\u0080` to `\u07FF` | 1 | 1 | 1 | 0 | bits 10-6 |||||
| `\u0000`, `\u0080` to `\u07FF` | 2 | 1 | 0 | bits 5-0 ||||||
| `\u0800` to `\uFFFF` | 1 | 1 | 1 | 1 | 0 | bits 15-12 ||||
| `\u0800` to `\uFFFF` | 2 | 1 | 0 | bits 11-6 ||||||
| `\u0800` to `\uFFFF` | 3 | 1 | 0 | bits 5-0 ||||||
|---|---|---|---|---|---|---|---|---|---|
[Encoding of UTF-8 values]
The 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.
- [Supplementary characters](https://developer.android.com/reference/java/lang/Character.html#unicode) are represented in the form of surrogate pairs.
**See also:**
- `https://developer.android.com/reference/java/io/DataInputStream`
- `https://developer.android.com/reference/java/io/DataOutput`
## Summary
| ### Public methods ||
|---|---|
| ` abstract boolean` | ` https://developer.android.com/reference/java/io/DataInput#readBoolean()() ` Reads one input byte and returns `true` if that byte is nonzero, `false` if that byte is zero. |
| ` abstract byte` | ` https://developer.android.com/reference/java/io/DataInput#readByte()() ` Reads and returns one input byte. |
| ` abstract char` | ` https://developer.android.com/reference/java/io/DataInput#readChar()() ` Reads two input bytes and returns a `char` value. |
| ` abstract double` | ` https://developer.android.com/reference/java/io/DataInput#readDouble()() ` Reads eight input bytes and returns a `double` value. |
| ` abstract float` | ` https://developer.android.com/reference/java/io/DataInput#readFloat()() ` Reads four input bytes and returns a `float` value. |
| ` abstract void` | ` https://developer.android.com/reference/java/io/DataInput#readFully(byte[])(byte[] b) ` Reads some bytes from an input stream and stores them into the buffer array `b`. |
| ` abstract void` | ` https://developer.android.com/reference/java/io/DataInput#readFully(byte[],%20int,%20int)(byte[] b, int off, int len) ` Reads `len` bytes from an input stream. |
| ` abstract int` | ` https://developer.android.com/reference/java/io/DataInput#readInt()() ` Reads four input bytes and returns an `int` value. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/io/DataInput#readLine()() ` Reads the next line of text from the input stream. |
| ` abstract long` | ` https://developer.android.com/reference/java/io/DataInput#readLong()() ` Reads eight input bytes and returns a `long` value. |
| ` abstract short` | ` https://developer.android.com/reference/java/io/DataInput#readShort()() ` Reads two input bytes and returns a `short` value. |
| ` abstract https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/io/DataInput#readUTF()() ` Reads in a string that has been encoded using a [modified UTF-8](https://developer.android.com/reference/java/io/DataInput#modified-utf-8) format. |
| ` abstract int` | ` https://developer.android.com/reference/java/io/DataInput#readUnsignedByte()() ` Reads one input byte, zero-extends it to type `int`, and returns the result, which is therefore in the range `0` through `255`. |
| ` abstract int` | ` https://developer.android.com/reference/java/io/DataInput#readUnsignedShort()() ` Reads two input bytes and returns an `int` value in the range `0` through `65535`. |
| ` abstract int` | ` https://developer.android.com/reference/java/io/DataInput#skipBytes(int)(int n) ` Makes an attempt to skip over `n` bytes of data from the input stream, discarding the skipped bytes. |
## Public methods
### readBoolean
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract boolean readBoolean ()
```
Reads one input byte and returns
`true` if that byte is nonzero,
`false` if that byte is zero.
This method is suitable for reading
the byte written by the `writeBoolean`
method of interface `DataOutput`.
| Returns ||
|---|---|
| `boolean` | the `boolean` value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readByte
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract byte readByte ()
```
Reads and returns one input byte.
The byte is treated as a signed value in
the range `-128` through `127`,
inclusive.
This method is suitable for
reading the byte written by the `writeByte`
method of interface `DataOutput`.
| Returns ||
|---|---|
| `byte` | the 8-bit value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readChar
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract char readChar ()
```
Reads two input bytes and returns a `char` value.
Let `a`
be the first byte read and `b`
be the second byte. The value
returned is:
(char)((a << 8) | (b & 0xff))
This method is suitable for reading bytes written by the `writeChar` method of interface `DataOutput`.
| Returns ||
|---|---|
| `char` | the `char` value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readDouble
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract double readDouble ()
```
Reads eight input bytes and returns
a `double` value. It does this
by first constructing a `long`
value in exactly the manner
of the `readLong`
method, then converting this `long`
value to a `double` in exactly
the manner of the method `Double.longBitsToDouble`.
This method is suitable for reading
bytes written by the `writeDouble`
method of interface `DataOutput`.
| Returns ||
|---|---|
| `double` | the `double` value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readFloat
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract float readFloat ()
```
Reads four input bytes and returns
a `float` value. It does this
by first constructing an `int`
value in exactly the manner
of the `readInt`
method, then converting this `int`
value to a `float` in
exactly the manner of the method `Float.intBitsToFloat`.
This method is suitable for reading
bytes written by the `writeFloat`
method of interface `DataOutput`.
| Returns ||
|---|---|
| `float` | the `float` value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readFully
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract void readFully (byte[] b)
```
Reads some bytes from an input
stream and stores them into the buffer
array `b`. The number of bytes
read is equal
to the length of `b`.
This method blocks until one of the
following conditions occurs:
- `b.length` bytes of input data are available, in which case a normal return is made.
- End of file is detected, in which case an `EOFException` is thrown.
- An I/O error occurs, in which case an `IOException` other than `EOFException` is thrown.
If `b` is `null`,
a `NullPointerException` is thrown.
If `b.length` is zero, then
no bytes are read. Otherwise, the first
byte read is stored into element `b[0]`,
the next one into `b[1]`, and
so on.
If an exception is thrown from
this method, then it may be that some but
not all bytes of `b` have been
updated with data from the input stream.
| Parameters ||
|---|---|
| `b` | `byte`: the buffer into which the data is read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if `b` is `null`. |
### readFully
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract void readFully (byte[] b,
int off,
int len)
```
Reads `len`
bytes from
an input stream.
This method
blocks until one of the following conditions
occurs:
- `len` bytes of input data are available, in which case a normal return is made.
- End of file is detected, in which case an `EOFException` is thrown.
- An I/O error occurs, in which case an `IOException` other than `EOFException` 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. Otherwise, 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`.
| Parameters ||
|---|---|
| `b` | `byte`: the buffer into which the data is read.
|
| `off` | `int`: an int specifying the offset in the data array `b`.
|
| `len` | `int`: an int specifying the number of bytes to read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
| `https://developer.android.com/reference/java/lang/IndexOutOfBoundsException` | if `off` is negative, `len` is negative, or `len` is greater than `b.length - off`. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if `b` is `null`. |
### readInt
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract int readInt ()
```
Reads four input bytes and returns an
`int` value. Let `a-d`
be the first through fourth bytes read. The value returned is:
(((a & 0xff) << 24) | ((b & 0xff) << 16) |
((c & 0xff) << 8) | (d & 0xff))
This method is suitable for reading bytes written by the `writeInt` method of interface `DataOutput`.
| Returns ||
|---|---|
| `int` | the `int` value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readLine
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract String readLine ()
```
Reads the next line of text from the input stream.
It reads successive bytes, converting
each byte separately into a character,
until it encounters a line terminator or
end of
file; the characters read are then
returned as a `String`. Note
that because this
method processes bytes,
it does not support input of the full Unicode
character set.
If end of file is encountered
before even one byte can be read, then `null`
is returned. Otherwise, each byte that is
read is converted to type `char`
by zero-extension. If the character `'\n'`
is encountered, it is discarded and reading
ceases. If the character `'\r'`
is encountered, it is discarded and, if
the following byte converts to the
character `'\n'`, then that is
discarded also; reading then ceases. If
end of file is encountered before either
of the characters `'\n'` and
`'\r'` is encountered, reading
ceases. Once reading has ceased, a `String`
is returned that contains all the characters
read and not discarded, taken in order.
Note that every character in this string
will have a value less than `\u0100`,
that is, `(char)256`.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | the next line of text from the input stream, or `null` if the end of file is encountered before a byte can be read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readLong
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract long readLong ()
```
Reads eight input bytes and returns
a `long` value. Let `a-h`
be the first through eighth bytes read.
The value returned is:
(((long)(a & 0xff) << 56) |
((long)(b & 0xff) << 48) |
((long)(c & 0xff) << 40) |
((long)(d & 0xff) << 32) |
((long)(e & 0xff) << 24) |
((long)(f & 0xff) << 16) |
((long)(g & 0xff) << 8) |
((long)(h & 0xff)))
This method is suitable
for reading bytes written by the `writeLong`
method of interface `DataOutput`.
| Returns ||
|---|---|
| `long` | the `long` value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readShort
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract short readShort ()
```
Reads two input bytes and returns
a `short` value. Let `a`
be the first byte read and `b`
be the second byte. The value
returned
is:
(short)((a << 8) | (b & 0xff))
This method is suitable for reading the bytes written by the `writeShort` method of interface `DataOutput`.
| Returns ||
|---|---|
| `short` | the 16-bit value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readUTF
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract String readUTF ()
```
Reads in a string that has been encoded using a
[modified UTF-8](https://developer.android.com/reference/java/io/DataInput#modified-utf-8)
format.
The general contract of `readUTF`
is that it reads a representation of a Unicode
character string encoded in modified
UTF-8 format; this string of characters
is then returned as a `String`.
First, two bytes are read and used to
construct an unsigned 16-bit integer in
exactly the manner of the `readUnsignedShort`
method . This integer value is called the
*UTF length* and specifies the number
of additional bytes to be read. These bytes
are then converted to characters by considering
them in groups. The length of each group
is computed from the value of the first
byte of the group. The byte following a
group, if any, is the first byte of the
next group.
If the first byte of a group
matches the bit pattern `0xxxxxxx`
(where `x` means "may be `0`
or `1`"), then the group consists
of just that byte. The byte is zero-extended
to form a character.
If the first byte
of a group matches the bit pattern `110xxxxx`,
then the group consists of that byte `a`
and a second byte `b`. If there
is no byte `b` (because byte
`a` was the last of the bytes
to be read), or if byte `b` does
not match the bit pattern `10xxxxxx`,
then a `UTFDataFormatException`
is thrown. Otherwise, the group is converted
to the character:
(char)(((a & 0x1F) << 6) | (b & 0x3F))
If the first byte of a group matches the bit pattern `1110xxxx`, then the group consists of that byte `a` and two more bytes `b` and `c`. If there is no byte `c` (because byte `a` was one of the last two of the bytes to be read), or either byte `b` or byte `c` does not match the bit pattern `10xxxxxx`, then a `UTFDataFormatException` is thrown. Otherwise, the group is converted to the character:
(char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))
If the first byte of a group matches the pattern `1111xxxx` or the pattern `10xxxxxx`, then a `UTFDataFormatException` is thrown.
If end of file is encountered
at any time during this entire process,
then an `EOFException` is thrown.
After every group has been converted to
a character by this process, the characters
are gathered, in the same order in which
their corresponding groups were read from
the input stream, to form a `String`,
which is returned.
The `writeUTF`
method of interface `DataOutput`
may be used to write data that is suitable
for reading by this method.
| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | a Unicode string.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
| `https://developer.android.com/reference/java/io/UTFDataFormatException` | if the bytes do not represent a valid modified UTF-8 encoding of a string. |
### readUnsignedByte
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract int readUnsignedByte ()
```
Reads one input byte, zero-extends
it to type `int`, and returns
the result, which is therefore in the range
`0`
through `255`.
This method is suitable for reading
the byte written by the `writeByte`
method of interface `DataOutput`
if the argument to `writeByte`
was intended to be a value in the range
`0` through `255`.
| Returns ||
|---|---|
| `int` | the unsigned 8-bit value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### readUnsignedShort
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract int readUnsignedShort ()
```
Reads two input bytes and returns
an `int` value in the range `0`
through `65535`. Let `a`
be the first byte read and
`b`
be the second byte. The value returned is:
(((a & 0xff) << 8) | (b & 0xff))
This method is suitable for reading the bytes written by the `writeShort` method of interface `DataOutput` if the argument to `writeShort` was intended to be a value in the range `0` through `65535`.
| Returns ||
|---|---|
| `int` | the unsigned 16-bit value read.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/EOFException` | if this stream reaches the end before reading all the bytes. |
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |
### skipBytes
Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public abstract int skipBytes (int n)
```
Makes an attempt to skip over
`n` bytes
of data from the input
stream, discarding the skipped bytes. However,
it may skip
over some smaller number of
bytes, possibly zero. This may result from
any of a
number of conditions; reaching
end of file before `n` bytes
have been skipped is
only one possibility.
This method never throws an `EOFException`.
The actual
number of bytes skipped is returned.
| Parameters ||
|---|---|
| `n` | `int`: the number of bytes to be skipped.
|
| Returns ||
|---|---|
| `int` | the number of bytes actually skipped.
|
| Throws ||
|---|---|
| `https://developer.android.com/reference/java/io/IOException` | if an I/O error occurs. |