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DataInputStream

public class DataInputStream
extends FilterInputStream implements DataInput

java.lang.Object
   ↳ java.io.InputStream
     ↳ java.io.FilterInputStream
       ↳ 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. 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.

See also:

Summary

Inherited fields

From class java.io.FilterInputStream

Public constructors

DataInputStream(InputStream in)

Creates a DataInputStream that uses the specified underlying InputStream.

Public methods

final int read(byte[] b)

Reads some number of bytes from the contained input stream and stores them into the buffer array b.

final 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.

final boolean readBoolean()

See the general contract of the readBoolean method of DataInput.

final byte readByte()

See the general contract of the readByte method of DataInput.

final char readChar()

See the general contract of the readChar method of DataInput.

final double readDouble()

See the general contract of the readDouble method of DataInput.

final float readFloat()

See the general contract of the readFloat method of DataInput.

final void readFully(byte[] b)

See the general contract of the readFully method of DataInput.

final void readFully(byte[] b, int off, int len)

See the general contract of the readFully method of DataInput.

final int readInt()

See the general contract of the readInt method of DataInput.

final String readLine()

This method was deprecated in API level 1. 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));
 

final long readLong()

See the general contract of the readLong method of DataInput.

final short readShort()

See the general contract of the readShort method of DataInput.

final String readUTF()

See the general contract of the readUTF method of DataInput.

static final 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.

final int readUnsignedByte()

See the general contract of the readUnsignedByte method of DataInput.

final int readUnsignedShort()

See the general contract of the readUnsignedShort method of DataInput.

final int skipBytes(int n)

See the general contract of the skipBytes method of DataInput.

Inherited methods

From class java.io.FilterInputStream
From class java.io.InputStream
From class java.lang.Object
From interface java.io.Closeable
From interface java.io.DataInput
From interface java.lang.AutoCloseable

Public constructors

DataInputStream

Added in API level 1
DataInputStream (InputStream in)

Creates a DataInputStream that uses the specified underlying InputStream.

Parameters
in InputStream: the specified input stream

Public methods

read

Added in API level 1
int read (byte[] b)

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)
 

Parameters
b byte: the buffer into which the data is read.
Returns
int 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:

read

Added in API level 1
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. 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.

Parameters
b byte: the buffer into which the data is read.
off int: the start offset in the destination array b
len int: the maximum number of bytes read.
Returns
int 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:

readBoolean

Added in API level 1
boolean readBoolean ()

See the general contract of the readBoolean method of DataInput.

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

Returns
boolean 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:

readByte

Added in API level 1
byte readByte ()

See the general contract of the readByte method of DataInput.

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

Returns
byte 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:

readChar

Added in API level 1
char readChar ()

See the general contract of the readChar method of DataInput.

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

Returns
char 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:

readDouble

Added in API level 1
double readDouble ()

See the general contract of the readDouble method of DataInput.

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

Returns
double 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:

readFloat

Added in API level 1
float readFloat ()

See the general contract of the readFloat method of DataInput.

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

Returns
float 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:

readFully

Added in API level 1
void readFully (byte[] b)

See the general contract of the readFully method of DataInput.

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

Parameters
b byte: 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:

readFully

Added in API level 1
void readFully (byte[] b, 
                int off, 
                int len)

See the general contract of the readFully method of DataInput.

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

Parameters
b byte: the buffer into which the data is read.
off int: the start offset of the data.
len int: 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:

readInt

Added in API level 1
int readInt ()

See the general contract of the readInt method of DataInput.

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

Returns
int 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:

readLine

Added in API level 1
String readLine ()

This method was deprecated in API level 1.
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.

Returns
String the next line of text from this input stream.
Throws
IOException if an I/O error occurs.

See also:

readLong

Added in API level 1
long readLong ()

See the general contract of the readLong method of DataInput.

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

Returns
long 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:

readShort

Added in API level 1
short readShort ()

See the general contract of the readShort method of DataInput.

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

Returns
short 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:

readUTF

Added in API level 1
String readUTF ()

See the general contract of the readUTF method of DataInput.

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

Returns
String 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

Added in API level 1
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. The details of the modified UTF-8 representation are exactly the same as for the readUTF method of DataInput.

Parameters
in DataInput: a data input stream.
Returns
String 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:

readUnsignedByte

Added in API level 1
int readUnsignedByte ()

See the general contract of the readUnsignedByte method of DataInput.

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

Returns
int 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:

readUnsignedShort

Added in API level 1
int readUnsignedShort ()

See the general contract of the readUnsignedShort method of DataInput.

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

Returns
int 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:

skipBytes

Added in API level 1
int skipBytes (int n)

See the general contract of the skipBytes method of DataInput.

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

Parameters
n int: the number of bytes to be skipped.
Returns
int 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.
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