Class DataInputStream
- java.lang.Object
-
- java.io.InputStream
-
- java.io.FilterInputStream
-
- java.io.DataInputStream
- All Implemented Interfaces:
-
Closeable
,DataInput
,AutoCloseable
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:
- 1.0
- See Also:
DataOutputStream
Field Summary
Fields declared in class java.io.FilterInputStream
in
Constructor Summary
Constructor | Description |
---|---|
DataInputStream(InputStream in) | Creates a DataInputStream that uses the specified underlying InputStream. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
int | read(byte[] b) | Reads some number of bytes from the contained input stream and stores them into the buffer array |
int | read(byte[] b,
int off,
int len) | Reads up to |
boolean | readBoolean() | See the general contract of the |
byte | readByte() | See the general contract of the |
char | readChar() | See the general contract of the |
double | readDouble() | See the general contract of the |
float | readFloat() | See the general contract of the |
void | readFully(byte[] b) | See the general contract of the |
void | readFully(byte[] b,
int off,
int len) | See the general contract of the |
int | readInt() | See the general contract of the |
String | readLine() | Deprecated. This method does not properly convert bytes to characters. |
long | readLong() | See the general contract of the |
short | readShort() | See the general contract of the |
int | readUnsignedByte() | See the general contract of the |
int | readUnsignedShort() | See the general contract of the |
String | readUTF() | See the general contract of the |
static String | readUTF(DataInput in) | Reads from the stream |
int | skipBytes(int n) | See the general contract of the |
Methods declared in class java.io.FilterInputStream
available, close, mark, markSupported, read, reset, skip
Methods declared in class java.io.InputStream
nullInputStream, readAllBytes, readNBytes, readNBytes, transferTo
Methods declared in 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 classFilterInputStream
- 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 classFilterInputStream
- Parameters:
-
b
- the buffer into which the data is read. -
off
- the start offset in the destination arrayb
-
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
- Ifb
isnull
. -
IndexOutOfBoundsException
- Ifoff
is negative,len
is negative, orlen
is greater thanb.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 interfaceDataInput
- Parameters:
-
b
- the buffer into which the data is read. - Throws:
-
NullPointerException
- ifb
isnull
. -
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 interfaceDataInput
- Parameters:
-
b
- the buffer into which the data is read. -
off
- the start offset in the data arrayb
. -
len
- the number of bytes to read. - Throws:
-
NullPointerException
- ifb
isnull
. -
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, orlen
is greater thanb.length - off
. -
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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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 interfaceDataInput
- 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
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 interfaceDataInput
- 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 interfaceDataInput
- 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()