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Class java.io.RandomAccessFile 

java.lang.Object
   |
   +----java.io.RandomAccessFile
public class RandomAccessFile
extends Object
implements DataOutput, DataInput
Instances of this class support both reading and writing to a random access file. An application can modify the position in the file at which the next read or write occurs. This class provides a sense of security by offering methods that allow specified mode accesses of read-only or read-write to files.

Constructor Index

o RandomAccessFile(File, String)
Creates a random access file stream to read from, and optionally to write to, the file specified by the File argument.
o RandomAccessFile(String, String)
Creates a random access file stream to read from, and optionally to write to, a file with the specified name.

Method Index

o close()
Closes this random access file stream and releases any system resources associated with the stream.
o getFD()
Returns the opaque file descriptor object associated with this stream.
o getFilePointer()
Returns the current offset in this file.
o length()
Returns the length of this file.
o read()
Reads a byte of data from this file.
o read(byte[])
Reads up to b.length bytes of data from this file into an array of bytes.
o read(byte[], int, int)
Reads up to len bytes of data from this file into an array of bytes.
o readBoolean()
Reads a boolean from this file.
o readByte()
Reads a signed 8-bit value from this file.
o readChar()
Reads a Unicode character from this file.
o readDouble()
Reads a double from this file.
o readFloat()
Reads a float from this file.
o readFully(byte[])
Reads b.length bytes from this file into the byte array.
o readFully(byte[], int, int)
Reads exactly len bytes from this file into the byte array.
o readInt()
Reads a signed 32-bit integer from this file.
o readLine()
Reads the next line of text from this file.
o readLong()
Reads a signed 64-bit integer from this file.
o readShort()
Reads a signed 16-bit number from this file.
o readUnsignedByte()
Reads an unsigned 8-bit number from this file.
o readUnsignedShort()
Reads an unsigned 16-bit number from this file.
o readUTF()
Reads in a string from this file.
o seek(long)
Sets the offset from the beginning of this file at which the next read or write occurs.
o skipBytes(int)
Skips exactly n bytes of input.
o write(byte[])
Writes b.length bytes from the specified byte array starting at offset off to this file.
o write(byte[], int, int)
Writes len bytes from the specified byte array starting at offset off to this file.
o write(int)
Writes the specified byte to this file.
o writeBoolean(boolean)
Writes a boolean to the file as a 1-byte value.
o writeByte(int)
Writes a byte to the file as a 1-byte value.
o writeBytes(String)
Writes the string to the file as a sequence of bytes.
o writeChar(int)
Writes a char to the file as a 2-byte value, high byte first.
o writeChars(String)
Writes a string to the file as a sequence of characters.
o writeDouble(double)
Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.
o writeFloat(float)
Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.
o writeInt(int)
Writes an int to the file as four bytes, high byte first.
o writeLong(long)
Writes a long to the file as eight bytes, high byte first.
o writeShort(int)
Writes a short to the file as two bytes, high byte first.
o writeUTF(String)
Writes a string to the file using UTF-8 encoding in a machine-independent manner.

Constructors

o RandomAccessFile 
    method RandomAccessFile(name=String, -
                            mode=String) public Signals IOException
Creates a random access file stream to read from, and optionally to write to, a file with the specified name.

The mode argument must either be equal to "r" or "rw", indicating either to open the file for input or for both input and output.

Parameters:
name - the system-dependent filename.
mode - the access mode.
Throws: IllegalArgumentException
if the mode argument is not equal to "r" or to "rw".
Throws: IOException
if an I/O error occurs.
Throws: SecurityException
if a security manager exists, its checkRead method is called with the name argument to see if the application is allowed read access to the file. If the mode argument is equal to "rw", its checkWrite method also is called with the name argument to see if the application is allowed write access to the file. Either of these may result in a security exception.
See Also:
SecurityException, checkRead
o RandomAccessFile 
    method RandomAccessFile(file=File, -
                            mode=String) public Signals IOException
Creates a random access file stream to read from, and optionally to write to, the file specified by the File argument.

The mode argument must either be equal to "r" or to "rw", indicating either to open the file for input, or for both input and output, respectively.

Parameters:
file - the file object.
mode - the access mode.
Throws: IllegalArgumentException
if the mode argument is not equal to "r" or to "rw".
Throws: IOException
if an I/O error occurs.
Throws: SecurityException
if a security manager exists, its checkRead method is called with the pathname of the File argument to see if the application is allowed read access to the file. If the mode argument is equal to "rw", its checkWrite method also is called with the pathname to see if the application is allowed write access to the file.
See Also:
getPath, checkRead

Methods

o getFD 
    method getFD() returns FileDescriptor public   final  Signals IOException
Returns the opaque file descriptor object associated with this stream.

Returns:
the file descriptor object associated with this stream.
Throws: IOException
if an I/O error occurs.
See Also:
FileDescriptor
o read 
    method read() returns int public     Signals IOException
Reads a byte of data from this file. This method blocks if no input is yet available.

Returns:
the next byte of data, or -1 if the end of the file is reached.
Throws: IOException
if an I/O error occurs.
o read 
    method read(b=byte[], -
                off=int, -
                len=int) returns int public     Signals IOException
Reads up to len bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

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 total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.
Throws: IOException
if an I/O error occurs.
o read 
    method read(b=byte[]) returns int public     Signals IOException
Reads up to b.length bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

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 this file has been reached.
Throws: IOException
if an I/O error occurs.
o readFully 
    method readFully(b=byte[])  public   final  Signals IOException
Reads b.length bytes from this file into the byte array. This method reads repeatedly from the file until all the bytes are read. This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Parameters:
b - the buffer into which the data is read.
Throws: EOFException
if this file reaches the end before reading all the bytes.
Throws: IOException
if an I/O error occurs.
o readFully 
    method readFully(b=byte[], -
                     off=int, -
                     len=int)  public   final  Signals IOException
Reads exactly len bytes from this file into the byte array. This method reads repeatedly from the file until all the bytes are read. This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Parameters:
b - the buffer into which the data is read.
off - the start offset of the data.
len - the number of bytes to read.
Throws: EOFException
if this file reaches the end before reading all the bytes.
Throws: IOException
if an I/O error occurs.
o skipBytes 
    method skipBytes(n=int) returns int public     Signals IOException
Skips exactly n bytes of input.

This method blocks until all the bytes are skipped, the end of the stream is detected, or an exception is thrown.

Parameters:
n - the number of bytes to be skipped.
Returns:
the number of bytes skipped, which is always n.
Throws: EOFException
if this file reaches the end before skipping all the bytes.
Throws: IOException
if an I/O error occurs.
o write 
    method write(b=int)  public     Signals IOException
Writes the specified byte to this file.

Parameters:
b - the byte to be written.
Throws: IOException
if an I/O error occurs.
o write 
    method write(b=byte[])  public     Signals IOException
Writes b.length bytes from the specified byte array starting at offset off to this file.

Parameters:
b - the data.
Throws: IOException
if an I/O error occurs.
o write 
    method write(b=byte[], -
                 off=int, -
                 len=int)  public     Signals IOException
Writes len bytes from the specified byte array starting at offset off to this file.

Parameters:
b - the data.
off - the start offset in the data.
len - the number of bytes to write.
Throws: IOException
if an I/O error occurs.
o getFilePointer 
    method getFilePointer() returns long public     Signals IOException
Returns the current offset in this file.

Returns:
the offset from the beginning of the file, in bytes, at which the next read or write occurs.
Throws: IOException
if an I/O error occurs.
o seek 
    method seek(pos=long)  public     Signals IOException
Sets the offset from the beginning of this file at which the next read or write occurs.

Parameters:
pos - the absolute position.
Throws: IOException
if an I/O error occurs.
o length 
    method length() returns long public     Signals IOException
Returns the length of this file.

Returns:
the length of this file.
Throws: IOException
if an I/O error occurs.
o close 
    method close()  public     Signals IOException
Closes this random access file stream and releases any system resources associated with the stream.

Throws: IOException
if an I/O error occurs.
o readBoolean 
    method readBoolean() returns boolean public   final  Signals IOException
Reads a boolean from this file. This method reads a single byte from the file. A value of 0 represents false. Any other value represents true. This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Returns:
the boolean value read.
Throws: EOFException
if this file has reached the end.
Throws: IOException
if an I/O error occurs.
o readByte 
    method readByte() returns byte public   final  Signals IOException
Reads a signed 8-bit value from this file. This method reads a byte from the file. If the byte read is b, where 0 <= b <= 255, then the result is:

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Returns:
the next byte of this file as a signed 8-bit byte.
Throws: EOFException
if this file has reached the end.
Throws: IOException
if an I/O error occurs.
o readUnsignedByte 
    method readUnsignedByte() returns int public   final  Signals IOException
Reads an unsigned 8-bit number from this file. This method reads a byte from this file and returns that byte.

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Returns:
the next byte of this file, interpreted as an unsigned 8-bit number.
Throws: EOFException
if this file has reached the end.
Throws: IOException
if an I/O error occurs.
o readShort 
    method readShort() returns short public   final  Signals IOException
Reads a signed 16-bit number from this file. The method reads 2 bytes from this file. If the two bytes read, in order, are b1 and b2, where each of the two values is between 0 and 255, inclusive, then the result is equal to:

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next two bytes of this file, interpreted as a signed 16-bit number.
Throws: EOFException
if this file reaches the end before reading two bytes.
Throws: IOException
if an I/O error occurs.
o readUnsignedShort 
    method readUnsignedShort() returns int public   final  Signals IOException
Reads an unsigned 16-bit number from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next two bytes of this file, interpreted as an unsigned 16-bit integer.
Throws: EOFException
if this file reaches the end before reading two bytes.
Throws: IOException
if an I/O error occurs.
o readChar 
    method readChar() returns char public   final  Signals IOException
Reads a Unicode character from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next two bytes of this file as a Unicode character.
Throws: EOFException
if this file reaches the end before reading two bytes.
Throws: IOException
if an I/O error occurs.
o readInt 
    method readInt() returns int public   final  Signals IOException
Reads a signed 32-bit integer from this file. This method reads 4 bytes from the file. If the bytes read, in order, are b1, b2, b3, and b4, where 0 <= b1, b2, b3, b4 <= 255, then the result is equal to:

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next four bytes of this file, interpreted as an int.
Throws: EOFException
if this file reaches the end before reading four bytes.
Throws: IOException
if an I/O error occurs.
o readLong 
    method readLong() returns long public   final  Signals IOException
Reads a signed 64-bit integer from this file. This method reads eight bytes from the file. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, where:

then the result is equal to: 

     ((long)b1 << 56) + ((long)b2 << 48)
     + ((long)b3 << 40) + ((long)b4 << 32)
     + ((long)b5 << 24) + ((long)b6 << 16)
     + ((long)b7 << 8) + b8

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next eight bytes of this file, interpreted as a long.
Throws: EOFException
if this file reaches the end before reading eight bytes.
Throws: IOException
if an I/O error occurs.
o readFloat 
    method readFloat() returns float public   final  Signals IOException
Reads a float from this file. This method reads an int value as if by the readInt method and then converts that int to a float using the intBitsToFloat method in class Float.

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next four bytes of this file, interpreted as a float.
Throws: EOFException
if this file reaches the end before reading four bytes.
Throws: IOException
if an I/O error occurs.
See Also:
readInt, intBitsToFloat
o readDouble 
    method readDouble() returns double public   final  Signals IOException
Reads a double from this file. This method reads a long value as if by the readLong method and then converts that long to a double using the longBitsToDouble method in class Double.

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
the next eight bytes of this file, interpreted as a double.
Throws: EOFException
if this file reaches the end before reading eight bytes.
Throws: IOException
if an I/O error occurs.
See Also:
readLong, longBitsToDouble
o readLine 
    method readLine() returns String public   final  Signals IOException
Reads the next line of text from this file. This method successively reads bytes from the file until it reaches the end of a line of text.

A line of text is terminated by a carriage-return character ('\r'), a newline character ('\n'), a carriage-return character immediately followed by a newline character, or the end of the input stream. The line-terminating character(s), if any, are included as part of the string returned.

This method blocks until a newline character is read, a carriage return and the byte following it are read (to see if it is a newline), the end of the stream is detected, or an exception is thrown.

Returns:
the next line of text from this file.
Throws: IOException
if an I/O error occurs.
o readUTF 
    method readUTF() returns String public   final  Signals IOException
Reads in a string from this file. The string has been encoded using a modified UTF-8 format.

The first two bytes are read as if by readUnsignedShort. This value gives the number of following bytes that are in the encoded string, not the length of the resulting string. The following bytes are then interpreted as bytes encoding characters in the UTF-8 format and are converted into characters.

This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Returns:
a Unicode string.
Throws: EOFException
if this file reaches the end before reading all the bytes.
Throws: IOException
if an I/O error occurs.
Throws: UTFDataFormatException
if the bytes do not represent valid UTF-8 encoding of a Unicode string.
See Also:
readUnsignedShort
o writeBoolean 
    method writeBoolean(v=boolean)  public   final  Signals IOException
Writes a boolean to the file as a 1-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0.

Parameters:
v - a boolean value to be written.
Throws: IOException
if an I/O error occurs.
o writeByte 
    method writeByte(v=int)  public   final  Signals IOException
Writes a byte to the file as a 1-byte value.

Parameters:
v - a byte value to be written.
Throws: IOException
if an I/O error occurs.
o writeShort 
    method writeShort(v=int)  public   final  Signals IOException
Writes a short to the file as two bytes, high byte first.

Parameters:
v - a short to be written.
Throws: IOException
if an I/O error occurs.
o writeChar 
    method writeChar(v=int)  public   final  Signals IOException
Writes a char to the file as a 2-byte value, high byte first.

Parameters:
v - a char value to be written.
Throws: IOException
if an I/O error occurs.
o writeInt 
    method writeInt(v=int)  public   final  Signals IOException
Writes an int to the file as four bytes, high byte first.

Parameters:
v - an int to be written.
Throws: IOException
if an I/O error occurs.
o writeLong 
    method writeLong(v=long)  public   final  Signals IOException
Writes a long to the file as eight bytes, high byte first.

Parameters:
v - a long to be written.
Throws: IOException
if an I/O error occurs.
o writeFloat 
    method writeFloat(v=float)  public   final  Signals IOException
Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.

Parameters:
v - a float value to be written.
Throws: IOException
if an I/O error occurs.
See Also:
floatToIntBits
o writeDouble 
    method writeDouble(v=double)  public   final  Signals IOException
Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.

Parameters:
v - a double value to be written.
Throws: IOException
if an I/O error occurs.
See Also:
doubleToLongBits
o writeBytes 
    method writeBytes(s=String)  public   final  Signals IOException
Writes the string to the file as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits.

Parameters:
s - a string of bytes to be written.
Throws: IOException
if an I/O error occurs.
o writeChars 
    method writeChars(s=String)  public   final  Signals IOException
Writes a string to the file as a sequence of characters. Each character is written to the data output stream as if by the writeChar method.

Parameters:
s - a String value to be written.
Throws: IOException
if an I/O error occurs.
See Also:
writeChar
o writeUTF 
    method writeUTF(str=String)  public   final  Signals IOException
Writes a string to the file using UTF-8 encoding in a machine-independent manner.

First, two bytes are written to the file as if by the writeShort method giving the number of bytes to follow. This value is the number of bytes actually written out, not the length of the string. Following the length, each character of the string is output, in sequence, using the UTF-8 encoding for each character.

Parameters:
str - a string to be written.
Throws: IOException
if an I/O error occurs. 
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