java.io
Class RandomAccessFile

java.lang.Object
  |
  +--java.io.RandomAccessFile

All Implemented Interfaces:

DataInput, DataOutput

public class RandomAccessFile

extends Object

implements DataOutput, DataInput

Random access files can be constructed from file descriptors, file names, or file objects. This class provides a sense of security by offering methods that allow specified mode accesses of read-only or read-write to files.

Constructor Summary

RandomAccessFile(File file, String mode)
Creates a RandomAccessFile from a specified File object and mode ("r" or "rw").

RandomAccessFile(String name, String mode)
Creates a RandomAccessFile with the specified system dependent file name and the specified mode.

Method Summary

void	close() Closes the file.
FileDescriptor	getFD() Returns the opaque file descriptor object.
long	getFilePointer() Returns the current location of the file pointer.
long	length() Returns the length of the file.
int	read() Reads a byte of data.
int	read(byte[] b) Reads data into an array of bytes.
int	read(byte[] b, int off, int len) Reads a sub array as a sequence of bytes.
boolean	readBoolean() Reads a boolean.
byte	readByte() Reads a byte.
char	readChar() Reads a 16 bit char.
double	readDouble() Reads a 64 bit double.
float	readFloat() Reads a 32 bit float.
void	readFully(byte[] b) Reads bytes, blocking until all bytes are read.
void	readFully(byte[] b, int off, int len) Reads bytes, blocking until all bytes are read.
int	readInt() Reads a 32 bit int.
String	readLine() Reads a line terminated by a '\n' or EOF.
long	readLong() Reads a 64 bit long.
short	readShort() Reads 16 bit short.
int	readUnsignedByte() Reads an unsigned 8 bit byte.
int	readUnsignedShort() Reads 16 bit short.
String	readUTF() Reads a UTF formatted String.
void	seek(long pos) Sets the file pointer to the specified absolute position.
int	skipBytes(int n) Skips bytes, block until all bytes are skipped.
void	write(byte[] b) Writes an array of bytes.
void	write(byte[] b, int off, int len) Wrotes a sub array of bytes.
void	write(int b) Writes a byte of data.
void	writeBoolean(boolean v) Writes a boolean.
void	writeByte(int v) Writes a byte.
void	writeBytes(String s) Writes a String as a sequence of bytes.
void	writeChar(int v) Writes a character.
void	writeChars(String s) Writes a String as a sequence of chars.
void	writeDouble(double v) Writes a 64 bit double.
void	writeFloat(float v) Writes a 32 bit float.
void	writeInt(int v) Writes an integer.
void	writeLong(long v) Writes a long.
void	writeShort(int v) Writes a short.
void	writeUTF(String str) Writes a String in UTF format.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RandomAccessFile

public RandomAccessFile(String name,
                        String mode)
                 throws IOException

Creates a RandomAccessFile with the specified system dependent file name and the specified mode. Mode "r" is for read-only and mode "rw" is for read+write.

Parameters:

name - the system dependent file name

mode - the access mode

Throws:

IOException - If an I/O error has occurred.

RandomAccessFile

public RandomAccessFile(File file,
                        String mode)
                 throws IOException

Creates a RandomAccessFile from a specified File object and mode ("r" or "rw").

Parameters:

file - the file object

mode - the access mode

Method Detail

getFD

public final FileDescriptor getFD()
                           throws IOException

Returns the opaque file descriptor object.

Returns:

the file descriptor.

IOException

read

public int read()
         throws IOException

Reads a byte of data. This method will block if no input is available.

Returns:

the byte read, or -1 if the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

read

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

Reads a sub array as a sequence of bytes.

Parameters:

b - the data to be written

off - the start offset in the data

len - the number of bytes that are written

Throws:

IOException - If an I/O error has occurred.

read

public int read(byte[] b)
         throws IOException

Reads data into an array of bytes. This method blocks until some input is available.

Returns:

the actual number of bytes read, -1 is returned when the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

readFully

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

Reads bytes, blocking until all bytes are read.

Specified by:

readFully in interface DataInput

Parameters:

b - the buffer into which the data is read

Returns:

the actual number of bytes read, -1 is returned when the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

readFully

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

Reads bytes, blocking until all bytes are read.

Specified by:

readFully in interface DataInput

Parameters:

b - the buffer into which the data is read

off - the start offset of the data

len - the maximum number of bytes read

Returns:

the actual number of bytes read, -1 is returned when the end of the stream is reached.

Throws:

IOException - If an I/O error has occurred.

skipBytes

public int skipBytes(int n)
              throws IOException

Description copied from interface: DataInput

Skips bytes, block until all bytes are skipped.

Specified by:

skipBytes in interface DataInput

Parameters:

n - the number of bytes to be skipped

Returns:

the actual number of bytes skipped.

Throws:

IOException - If other I/O error has occurred.

write

public void write(int b)
           throws IOException

Writes a byte of data. This method will block until the byte is actually written.

Specified by:

write in interface DataOutput

Parameters:

b - the byte to be written

Throws:

IOException - If an I/O error has occurred.

write

public void write(byte[] b)
           throws IOException

Writes an array of bytes. Will block until the bytes are actually written.

Specified by:

write in interface DataOutput

Parameters:

b - the data to be written

Throws:

IOException - If an I/O error has occurred.

write

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

Wrotes a sub array of bytes.

Specified by:

write in interface DataOutput

Parameters:

b - the data to be written

off - the start offset in the data

len - the number of bytes that are written

Throws:

IOException - If an I/O error has occurred.

getFilePointer

public long getFilePointer()
                    throws IOException

Returns the current location of the file pointer.

IOException

seek

public void seek(long pos)
          throws IOException

Sets the file pointer to the specified absolute position.

Parameters:

pos - the absolute position

IOException

length

public long length()
            throws IOException

Returns the length of the file.

IOException

close

public void close()
           throws IOException

Closes the file.

Throws:

IOException - If an I/O error has occurred.

readBoolean

public final boolean readBoolean()
                          throws IOException

Reads a boolean.

Specified by:

readBoolean in interface DataInput

Returns:

the boolean read.

Throws:

IOException - If other I/O error has occurred.

readByte

public final byte readByte()
                    throws IOException

Reads a byte.

Specified by:

readByte in interface DataInput

Returns:

the 8 bit byte read.

Throws:

IOException - If other I/O error has occurred.

readUnsignedByte

public final int readUnsignedByte()
                           throws IOException

Reads an unsigned 8 bit byte.

Specified by:

readUnsignedByte in interface DataInput

Returns:

the 8 bit byte read.

Throws:

IOException - If other I/O error has occurred.

readShort

public final short readShort()
                      throws IOException

Reads 16 bit short.

Specified by:

readShort in interface DataInput

Returns:

the read 16 bit short.

Throws:

IOException - If other I/O error has occurred.

readUnsignedShort

public final int readUnsignedShort()
                            throws IOException

Reads 16 bit short.

Specified by:

readUnsignedShort in interface DataInput

Returns:

the read 16 bit short.

Throws:

IOException - If other I/O error has occurred.

readChar

public final char readChar()
                    throws IOException

Reads a 16 bit char.

Specified by:

readChar in interface DataInput

Returns:

the read 16 bit char.

Throws:

IOException - If other I/O error has occurred.

readInt

public final int readInt()
                  throws IOException

Reads a 32 bit int.

Specified by:

readInt in interface DataInput

Returns:

the read 32 bit integer.

Throws:

IOException - If other I/O error has occurred.

readLong

public final long readLong()
                    throws IOException

Reads a 64 bit long.

Specified by:

readLong in interface DataInput

Returns:

the read 64 bit long.

Throws:

IOException - If other I/O error has occurred.

readFloat

public final float readFloat()
                      throws IOException

Reads a 32 bit float.

Specified by:

readFloat in interface DataInput

Returns:

the read 32 bit float.

Throws:

IOException - If other I/O error has occurred.

readDouble

public final double readDouble()
                        throws IOException

Reads a 64 bit double.

Specified by:

readDouble in interface DataInput

Returns:

the read 64 bit double.

Throws:

IOException - If other I/O error has occurred.

readLine

public final String readLine()
                      throws IOException

Reads a line terminated by a '\n' or EOF.

Specified by:

readLine in interface DataInput

IOException

readUTF

public final String readUTF()
                     throws IOException

Reads a UTF formatted String.

Specified by:

readUTF in interface DataInput

IOException

writeBoolean

public final void writeBoolean(boolean v)
                        throws IOException

Writes a boolean.

Specified by:

writeBoolean in interface DataOutput

Parameters:

v - the boolean value

IOException

writeByte

public final void writeByte(int v)
                     throws IOException

Writes a byte.

Specified by:

writeByte in interface DataOutput

Parameters:

v - the byte

IOException

writeShort

public final void writeShort(int v)
                      throws IOException

Writes a short.

Specified by:

writeShort in interface DataOutput

Parameters:

v - the short

IOException

writeChar

public final void writeChar(int v)
                     throws IOException

Writes a character.

Specified by:

writeChar in interface DataOutput

Parameters:

v - the char

IOException

writeInt

public final void writeInt(int v)
                    throws IOException

Writes an integer.

Specified by:

writeInt in interface DataOutput

Parameters:

v - the integer

IOException

writeLong

public final void writeLong(long v)
                     throws IOException

Writes a long.

Specified by:

writeLong in interface DataOutput

Parameters:

v - the long

IOException

writeFloat

public final void writeFloat(float v)
                      throws IOException

Description copied from interface: DataOutput

Writes a 32 bit float.

Specified by:

writeFloat in interface DataOutput

Parameters:

v - the float value to be written

IOException

writeDouble

public final void writeDouble(double v)
                       throws IOException

Description copied from interface: DataOutput

Writes a 64 bit double.

Specified by:

writeDouble in interface DataOutput

Parameters:

v - the double value to be written

IOException

writeBytes

public final void writeBytes(String s)
                      throws IOException

Writes a String as a sequence of bytes.

Specified by:

writeBytes in interface DataOutput

Parameters:

s - the String

IOException

writeChars

public final void writeChars(String s)
                      throws IOException

Writes a String as a sequence of chars.

Specified by:

writeChars in interface DataOutput

Parameters:

s - the String

IOException

writeUTF

public final void writeUTF(String str)
                    throws IOException

Writes a String in UTF format.

Specified by:

writeUTF in interface DataOutput

Parameters:

str - the String

IOException