Полезная информация

Java Fundamental Classes Reference

Previous Chapter 11
The java.io Package
Next
 

DataInputStream

Name

DataInputStream

Synopsis

Class Name:

java.io.DataInputStream

Superclass:

java.io.FilterInputStream

Immediate Subclasses:

None

Interfaces Implemented:

java.io.DataInput

Availability:

JDK 1.0 or later

Description

The DataInputStream class provides methods for reading primitive data types and lines of text from an underlying input stream in a machine-independent manner. Many of the methods of DataInputStream read a single primitive data type, in binary format, from an underlying input stream. All multibyte quantities are assumed to be in a format that stores the most significant byte as the first byte and the least significant byte as the last byte.

Class Summary

public class java.io.DataInputStream extends java.io.FilterInputStream
                                     implements java.io.DataInput {
  // Constructors
  public DataInputStream(InputStream in);
  // Class Methods
  public final static String readUTF(DataInput in);
  // Instance Methods
  public final int read(byte[] b);
  public final int read(byte[] b, int off, int len);
  public final boolean readBoolean();
  public final byte readByte();
  public final char readChar();
  public final double readDouble();
  public final float readFloat();
  public final void readFully(byte[] b);
  public final void readFully(byte[] b, int off, int len);
  public final int readInt();
  public final String readLine();                // Deprecated in 1.1
  public final long readLong();
  public final short readShort();
  public final int readUnsignedByte();
  public final int readUnsignedShort();
  public final String readUTF() throws IOException;
  public final int skipBytes(int n) throws IOException;
}

Constructors

DataInputStream

public DataInputStream(InputStream in)

Parameters

in

The input stream to use.

Description

This constructor creates a DataInputStream object that reads from, or wraps, the given input stream.

Class Methods

readUTF

 public final static String readUTF(DataInput in) throws IOException 

Parameters

in

The data input stream to use.

Returns

The String read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

UTFDataFormatException

If the bytes do not represent a valid UTF-8 encoding.

Description

This method reads a UTF-8 encoded string from the given DataInput object. To get the number of bytes in the encoded string, the first two bytes are read as an unsigned short value. Then the following bytes are read and interpreted as UTF-8 encoded bytes; these bytes are converted into characters for the resulting String. This method blocks until all of the bytes in the encoded string have been read, the end of the stream is encountered, or an exception is thrown.

For details on the UTF-8 encoding, see Appendix B, The UTF-8 Encoding.

Instance Methods

read

public final int read(byte b[]) throws IOException

Parameters

b

An array of bytes to be filled from the stream.

Returns

The number of bytes read, or -1 if the end of file is encountered immediately.

Throws

IOException

If any kind of I/O error occurs.

Overrides

FilterInputStream.read(byte[])

Description

This method reads bytes of input into the given array by calling the read() method of the underlying stream. The method reads up to b.length bytes of data from the stream. The method blocks until there is some input available.

 public final int read(byte b[], int off, int len) throws IOException 

Parameters

b

An array of bytes to be filled from the stream.

off

An offset into the byte array.

len

The number of bytes to read.

Returns

The number of bytes read, or -1 if the end of file is encountered immediately.

Throws

IOException

If any kind of I/O error occurs.

Overrides

FilterInputStream.read(byte[], int, int)

Description

This method reads up to len bytes of input into the given array starting at index off. The method reads the bytes by calling the read() method of the underlying stream and blocks until there is some input available.

readBoolean

public final boolean readBoolean() throws IOException

Returns

The boolean value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readBoolean()

Description

This method reads a byte as a boolean value from the underlying input stream. A byte that contains a zero is read as false; that which contains any other value is read as true. The method blocks until the byte is read, the end of the stream is encountered, or an exception is thrown.

readByte

public final byte readByte() throws IOException

Returns

The byte value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readByte()

Description

This method reads a signed 8-bit value--a byte--from the underlying input stream. The method blocks until the byte is read, the end of the stream is encountered, or an exception is thrown.

readChar

public final char readChar() throws IOException

Returns

The char value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readChar()

Description

This method reads a 16-bit Unicode character from the stream. The method reads two bytes from the underlying input stream and then creates a char value, using the first byte read as the most significant byte. The method blocks until the two bytes are read, the end of the stream is encountered, or an exception is thrown.

readDouble

public final double readDouble() throws IOException

Returns

The double value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readDouble()

Description

This method reads a 64-bit double quantity from the stream. The method reads a long value from the underlying input stream as if using the readLong() method. The long value is then converted to a double using the longBitsToDouble() method in Double. The method blocks until the necessary eight bytes are read, the end of the stream is encountered, or an exception is thrown.

readFloat

public final float readFloat() throws IOException

Returns

The float value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readFloat()

Description

This method reads a 32-bit float quantity from the stream. The method reads an int value from the underlying input stream as if using the readInt() method. The int value is then converted to a float using the intBitsToFloat() method in Float. The method blocks until the necessary four bytes are read, the end of the stream is encountered, or an exception is thrown.

readFully

public final void readFully(byte b[]) throws IOException

Parameters

b

The array to fill.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readFully(byte[])

Description

This method reads bytes into the given array b until the array is full. The method reads repeatedly from the underlying stream to fill the array. The method blocks until all of the bytes are read, the end of the stream is encountered, or an exception is thrown.

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

Parameters

b

The array to fill.

off

An offset into the array.

len

The number of bytes to read.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readFully(byte[], int, int)

Description

This method reads len bytes into the given array, starting at offset off. The method reads repeatedly from the underlying stream to fill the array. The method blocks until all the bytes are read, the end of the stream is encountered, or an exception is thrown.

readInt

public final int readInt() throws IOException

Returns

The int value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readInt()

Description

This method reads a signed 32-bit int quantity from the stream. The method reads four bytes from the underlying input stream and then creates an int quantity, using the first byte read as the most significant byte. The method blocks until the four bytes are read, the end of the stream is encountered, or an exception is thrown.

readLine

public final String readLine() throws IOException

Availability

Deprecated as of JDK 1.1

Returns

A String that contains the line read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other I/O error occurs.

Implements

DataInput.readLine()

Description

This method reads the next line of text from the stream. The method reads bytes of data from the underlying input stream until it encounters a line terminator. A line terminator is a carriage return ("\r"), a newline character ("\n"), a carriage return immediately followed by a newline character, or the end of the stream. The method blocks until a line terminator is read, the end of the stream is encountered, or an exception is thrown.

This method is deprecated as of JDK 1.1 because it does not convert bytes to characters correctly. It's replaced by BufferedReader.readLine().

readLong

public final long readLong() throws IOException

Returns

The long value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readLong()

Description

This method reads a signed 64-bit long quantity from the stream. The method reads eight bytes from the underlying input stream and then creates a long quantity, using the first byte read as the most significant byte. The method blocks until the eight bytes are read, the end of the stream is encountered, or an exception is thrown.

readShort

public final short readShort() throws IOException

Returns

The short value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readShort()

Description

This method reads a signed 16-bit short quantity from the stream. The method reads two bytes from the underlying input stream and then creates a short quantity, using the first byte read as the most significant byte. The method blocks until the two bytes are read, the end of the stream is encountered, or an exception is thrown.

readUnsignedByte

public final int readUnsignedByte() throws IOException

Returns

The unsigned byte value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readUnsignedByte()

Description

This method reads an unsigned 8-bit quantity from the stream. The method reads a byte from the underlying input stream and returns that byte, and blocks until the byte is read, the end of the stream is encountered, or an exception is thrown.

readUnsignedShort

public final int readUnsignedShort() throws IOException

Returns

The unsigned short value read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

Implements

DataInput.readUnsignedShort()

Description

This method reads an unsigned 16-bit quantity from the stream. The method reads two bytes from the underlying input stream and creates an unsigned short quantity, using the first byte read as the most significant byte. The method blocks until the two bytes are read, the end of the stream is encountered, or an exception is thrown.

readUTF

public final String readUTF() throws IOException

Returns

The String read from the stream.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind of I/O error occurs.

UTFDataFormatException

If the bytes do not represent a valid UTF-8 encoding.

Implements

DataInput.readUTF()

Description

This method reads a UTF-8 encoded string from the stream. See the description of the readUTF(DataInput) class method for more information.

skipBytes

public final int skipBytes(int n) throws IOException

Parameters

n

The number of bytes to skip.

Returns

The actual number of skipped bytes.

Throws

EOFException

If the end of the file is encountered.

IOException

If any other kind I/O error occurs.

Implements

DataInput.skipBytes()

Description

This method skips over n bytes in the underlying input stream. The method blocks until all of the bytes are skipped, the end of the stream is encountered, or an exception is thrown.

Inherited Methods

Method

Inherited From

Method

Inherited From

available ()

FilterInputStream

clone()

Object

close()

FilterInputStream

equals(Object)

Object

finalize()

Object

getClass()

Object

hashCode()

Object

mark(int)

FilterInputStream

markSupported()

FilterInputStream

notify()

Object

notifyAll()

Object

read()

FilterInputStream

reset()

FilterInputStream

skip(long)

FilterInputStream

toString()

Object

wait()

Object

wait(long)

Object

wait(long, int)

Object

See Also

DataOutputStream, Double, EOFException, FilterInputStream, Float, InputStream, IOException, String, UTFDataFormatException


Previous Home Next
DataInput Book Index DataOutput

Java in a Nutshell Java Language Reference Java AWT Java Fundamental Classes Exploring Java