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

protected InputStream in

The input stream to be filtered.

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 is 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));
 

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

int available()

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream.

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, int off, int len)

Reads up to len bytes of data from this input stream into an array of bytes.

int read(byte[] b)

Reads up to b.length bytes of data from this input stream into an array of bytes.

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 available()

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking, which may be 0, or 0 when end of stream is detected.

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.

static InputStream nullInputStream()

Returns a new InputStream that reads no bytes.

int read(byte[] b)

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

abstract int read()

Reads the next byte of data from the input stream.

int read(byte[] b, int off, int len)

Reads up to len bytes of data from the input stream into an array of bytes.

byte[] readAllBytes()

Reads all remaining bytes from the input stream.

int readNBytes(byte[] b, int off, int len)

Reads the requested number of bytes from the input stream into the given byte array.

byte[] readNBytes(int len)

Reads up to a specified number of bytes from the input stream.

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 this input stream.

void skipNBytes(long n)

Skips over and discards exactly n bytes of data from this input stream.

long transferTo(OutputStream out)

Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read.

Object clone()

Creates and returns a copy of this object.

boolean equals(Object obj)

Indicates whether some other object is "equal to" this one.

void finalize()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

final Class<?> getClass()

Returns the runtime class of this Object.

int hashCode()

Returns a hash code value for the object.

final void notify()

Wakes up a single thread that is waiting on this object's monitor.

final void notifyAll()

Wakes up all threads that are waiting on this object's monitor.

String toString()

Returns a string representation of the object.

final void wait(long timeoutMillis, int nanos)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void wait(long timeoutMillis)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void wait()

Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

abstract void close()

Closes this stream and releases any system resources associated with it.

abstract boolean readBoolean()

Reads one input byte and returns true if that byte is nonzero, false if that byte is zero.

abstract byte readByte()

Reads and returns one input byte.

abstract char readChar()

Reads two input bytes and returns a char value.

abstract double readDouble()

Reads eight input bytes and returns a double value.

abstract float readFloat()

Reads four input bytes and returns a float value.

abstract void readFully(byte[] b)

Reads some bytes from an input stream and stores them into the buffer array b.

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

Reads len bytes from an input stream.

abstract int readInt()

Reads four input bytes and returns an int value.

abstract String readLine()

Reads the next line of text from the input stream.

abstract long readLong()

Reads eight input bytes and returns a long value.

abstract short readShort()

Reads two input bytes and returns a short value.

abstract String readUTF()

Reads in a string that has been encoded using a modified UTF-8 format.

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.

abstract int readUnsignedShort()

Reads two input bytes and returns an int value in the range 0 through 65535.

abstract int skipBytes(int n)

Makes an attempt to skip over n bytes of data from the input stream, discarding the skipped bytes.

abstract void close()

Closes this resource, relinquishing any underlying resources.

Public constructors

DataInputStream

Added in API level 1
public 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
public final 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.

read

Added in API level 1
public 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. 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.

readBoolean

Added in API level 1
public final 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.

readByte

Added in API level 1
public final 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.

readChar

Added in API level 1
public final 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.

readDouble

Added in API level 1
public final 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.

readFloat

Added in API level 1
public final 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.

readFully

Added in API level 1
public final 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
NullPointerException if b is null.
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.

readFully

Added in API level 1
public final 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 in the data array b.

len int: the number of bytes to read.

Throws
NullPointerException if b is null.
IndexOutOfBoundsException if off is negative, len is negative, or len is greater than b.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.

readInt

Added in API level 1
public final 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.

readLine

Added in API level 1
public final String readLine ()

This method is 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.

Returns
String the next line of text from this input stream.

Throws
IOException if an I/O error occurs.

readLong

Added in API level 1
public final 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.

readShort

Added in API level 1
public final 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.

readUTF

Added in API level 1
public final 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.

readUTF

Added in API level 1
public 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. 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.

readUnsignedByte

Added in API level 1
public final 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.

readUnsignedShort

Added in API level 1
public final 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.

skipBytes

Added in API level 1
public final 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.