Class XRandomAccessFile
- All Implemented Interfaces:
DataInput
,DataOutput
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Constructor Summary
ConstructorsConstructorDescriptionXRandomAccessFile
(XFile xf, String mode) Creates a random access file stream to read from, and optionally to write to, the file specified by theXFile
argument.XRandomAccessFile
(String name, String mode) Creates a random access file to read from, and optionally to write to, a file with the specified name. -
Method Summary
Modifier and TypeMethodDescriptionvoid
close()
Closes this random access file and flushes any unwritten data to the file.void
flush()
Forces any buffered output bytes to be written out.long
Returns the current offset in this file.long
length()
Returns the length of this file.int
read()
Reads a byte of data from this file.int
read
(byte[] b) Reads up tob.length
bytes of data from this file into an array of bytes.int
read
(byte[] b, int off, int len) Reads up tolen
bytes of data from this file into an array of bytes.final boolean
Reads aboolean
from this file.final byte
readByte()
Reads a signed 8-bit value from this file.final char
readChar()
Reads a Unicode character from this file.final double
Reads adouble
from this file.final float
Reads afloat
from this file.final void
readFully
(byte[] b) Readsb.length
bytes from this file into the byte array.final void
readFully
(byte[] b, int off, int len) Reads exactlylen
bytes from this file into the byte array.final int
readInt()
Reads a signed 32-bit integer from this file.final String
readLine()
Reads the next line of text from this file.final long
readLong()
Reads a signed 64-bit integer from this file.final short
Reads a signed 16-bit number from this file.final int
Reads an unsigned 8-bit number from this file.final int
Reads an unsigned 16-bit number from this file.final String
readUTF()
Reads in a string from this file.void
seek
(long pos) Sets the offset from the beginning of this file at which the next read or write occurs.int
skipBytes
(int n) Skips exactlyn
bytes of input.void
write
(byte[] b) Writesb.length
bytes from the specified byte array starting at offsetoff
to this file.void
write
(byte[] b, int off, int len) Writeslen
bytes from the specified byte array starting at offsetoff
to this file.void
write
(int b) Writes the specified byte to this file.final void
writeBoolean
(boolean v) Writes aboolean
to the file as a 1-byte value.final void
writeByte
(int v) Writes abyte
to the file as a 1-byte value.final void
writeBytes
(String s) Writes the string to the file as a sequence of bytes.final void
writeChar
(int v) Writes achar
to the file as a 2-byte value, high byte first.final void
writeChars
(String s) Writes a string to the file as a sequence of characters.final void
writeDouble
(double v) Converts the double argument to along
using thedoubleToLongBits
method in classDouble
, and then writes thatlong
value to the file as an 8-byte quantity, high byte first.final void
writeFloat
(float v) Converts the float argument to anint
using thefloatToIntBits
method in classFloat
, and then writes thatint
value to the file as a 4-byte quantity, high byte first.final void
writeInt
(int v) Writes anint
to the file as four bytes, high byte first.final void
writeLong
(long v) Writes along
to the file as eight bytes, high byte first.final void
writeShort
(int v) Writes ashort
to the file as two bytes, high byte first.final void
Writes a string to the file using UTF-8 encoding in a machine-independent manner.
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Constructor Details
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XRandomAccessFile
Creates a random access file stream to read from, and optionally to write to, the file specified by theXFile
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:
xf
- the XFile object.mode
- the access mode.- Throws:
IllegalArgumentException
- if the mode argument is not equal to"r"
or to"rw"
.IOException
- if an I/O error occurs.
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XRandomAccessFile
Creates a random access file 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 native or URL file name.mode
- the access mode.- Throws:
IllegalArgumentException
- if the mode argument is not equal to"r"
or to"rw"
.IOException
- if an I/O error occurs.
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Method Details
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read
Reads a byte of data from this file.- Returns:
- the next byte of data, or
-1
if the end of the file is reached. - Throws:
IOException
- if an I/O error occurs.
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read
Reads up tolen
bytes of data from this file into an array of bytes.- 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.
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read
Reads up tob.length
bytes of data from this file into an array of bytes.- 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.
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readFully
Readsb.length
bytes from this file into the byte array.- Specified by:
readFully
in interfaceDataInput
- Parameters:
b
- the buffer into which the data is read.- Throws:
EOFException
- if this file reaches the end before reading all the bytes.IOException
- if an I/O error occurs.
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readFully
Reads exactlylen
bytes from this file into the byte array.- Specified by:
readFully
in interfaceDataInput
- 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.IOException
- if an I/O error occurs.
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skipBytes
Skips exactlyn
bytes of input.- Specified by:
skipBytes
in interfaceDataInput
- 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.IOException
- if an I/O error occurs.
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write
Writes the specified byte to this file.- Specified by:
write
in interfaceDataOutput
- Parameters:
b
- thebyte
to be written.- Throws:
IOException
- if an I/O error occurs.
-
write
Writesb.length
bytes from the specified byte array starting at offsetoff
to this file.- Specified by:
write
in interfaceDataOutput
- Parameters:
b
- the data.- Throws:
IOException
- if an I/O error occurs.
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write
Writeslen
bytes from the specified byte array starting at offsetoff
to this file.- Specified by:
write
in interfaceDataOutput
- 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.
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getFilePointer
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.
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seek
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.
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length
Returns the length of this file.- Returns:
- the length of this file.
- Throws:
IOException
- if an I/O error occurs.
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flush
Forces any buffered output bytes to be written out.- Throws:
IOException
- if an I/O error occurs.
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close
Closes this random access file and flushes any unwritten data to the file. After the file is closed further I/O operations may throw IOException.- Throws:
IOException
- if an I/O error occurs.
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readBoolean
Reads aboolean
from this file. This method reads a single byte from the file. A value of0
representsfalse
. Any other value representstrue
. This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.- Specified by:
readBoolean
in interfaceDataInput
- Returns:
- the
boolean
value read. - Throws:
EOFException
- if this file has reached the end.IOException
- if an I/O error occurs.
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readByte
Reads a signed 8-bit value from this file. This method reads a byte from the file. If the byte read isb
, where0 <= b <= 255
, then the result is:(byte)(b)
This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readByte
in interfaceDataInput
- Returns:
- the next byte of this file as a signed 8-bit
byte
. - Throws:
EOFException
- if this file has reached the end.IOException
- if an I/O error occurs.
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readUnsignedByte
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.
- Specified by:
readUnsignedByte
in interfaceDataInput
- Returns:
- the next byte of this file, interpreted as an unsigned 8-bit number.
- Throws:
EOFException
- if this file has reached the end.IOException
- if an I/O error occurs.
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readShort
Reads a signed 16-bit number from this file. The method reads 2 bytes from this file. If the two bytes read, in order, areb1
andb2
, where each of the two values is between0
and255
, inclusive, then the result is equal to:(short)((b1 << 8) | b2)
This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readShort
in interfaceDataInput
- 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.IOException
- if an I/O error occurs.
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readUnsignedShort
Reads an unsigned 16-bit number from this file. This method reads two bytes from the file. If the bytes read, in order, areb1
andb2
, where0 <= b1, b2 <= 255
, then the result is equal to:(b1 << 8) | b2
This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readUnsignedShort
in interfaceDataInput
- 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.IOException
- if an I/O error occurs.
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readChar
Reads a Unicode character from this file. This method reads two bytes from the file. If the bytes read, in order, areb1
andb2
, where0 <= b1, b2 <= 255
, then the result is equal to:(char)((b1 << 8) | b2)
This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readChar
in interfaceDataInput
- Returns:
- the next two bytes of this file as a Unicode character.
- Throws:
EOFException
- if this file reaches the end before reading two bytes.IOException
- if an I/O error occurs.
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readInt
Reads a signed 32-bit integer from this file. This method reads 4 bytes from the file. If the bytes read, in order, areb1
,b2
,b3
, andb4
, where0 <= b1, b2, b3, b4 <= 255
, then the result is equal to:(b1 << 24) | (b2 << 16) + (b3 << 8) + b4
This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readInt
in interfaceDataInput
- Returns:
- the next four bytes of this file, interpreted as an
int
. - Throws:
EOFException
- if this file reaches the end before reading four bytes.IOException
- if an I/O error occurs.
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readLong
Reads a signed 64-bit integer from this file. This method reads eight bytes from the file. If the bytes read, in order, areb1
,b2
,b3
,b4
,b5
,b6
,b7
, andb8,
where:0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
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.
- Specified by:
readLong
in interfaceDataInput
- Returns:
- the next eight bytes of this file, interpreted as a
long
. - Throws:
EOFException
- if this file reaches the end before reading eight bytes.IOException
- if an I/O error occurs.
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readFloat
Reads afloat
from this file. This method reads anint
value as if by thereadInt
method and then converts thatint
to afloat
using theintBitsToFloat
method in classFloat
.This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readFloat
in interfaceDataInput
- Returns:
- the next four bytes of this file, interpreted as a
float
. - Throws:
EOFException
- if this file reaches the end before reading four bytes.IOException
- if an I/O error occurs.- See Also:
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readDouble
Reads adouble
from this file. This method reads along
value as if by thereadLong
method and then converts thatlong
to adouble
using thelongBitsToDouble
method in classDouble
.This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.
- Specified by:
readDouble
in interfaceDataInput
- Returns:
- the next eight bytes of this file, interpreted as a
double
. - Throws:
EOFException
- if this file reaches the end before reading eight bytes.IOException
- if an I/O error occurs.- See Also:
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readLine
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.
- Specified by:
readLine
in interfaceDataInput
- Returns:
- the next line of text from this file.
- Throws:
IOException
- if an I/O error occurs.
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readUTF
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.
- Specified by:
readUTF
in interfaceDataInput
- Returns:
- a Unicode string.
- Throws:
EOFException
- if this file reaches the end before reading all the bytes.IOException
- if an I/O error occurs.UTFDataFormatException
- if the bytes do not represent valid UTF-8 encoding of a Unicode string.- See Also:
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writeBoolean
Writes aboolean
to the file as a 1-byte value. The valuetrue
is written out as the value(byte)1
; the valuefalse
is written out as the value(byte)0
.- Specified by:
writeBoolean
in interfaceDataOutput
- Parameters:
v
- aboolean
value to be written.- Throws:
IOException
- if an I/O error occurs.
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writeByte
Writes abyte
to the file as a 1-byte value.- Specified by:
writeByte
in interfaceDataOutput
- Parameters:
v
- abyte
value to be written.- Throws:
IOException
- if an I/O error occurs.
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writeShort
Writes ashort
to the file as two bytes, high byte first.- Specified by:
writeShort
in interfaceDataOutput
- Parameters:
v
- ashort
to be written.- Throws:
IOException
- if an I/O error occurs.
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writeChar
Writes achar
to the file as a 2-byte value, high byte first.- Specified by:
writeChar
in interfaceDataOutput
- Parameters:
v
- achar
value to be written.- Throws:
IOException
- if an I/O error occurs.
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writeInt
Writes anint
to the file as four bytes, high byte first.- Specified by:
writeInt
in interfaceDataOutput
- Parameters:
v
- anint
to be written.- Throws:
IOException
- if an I/O error occurs.
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writeLong
Writes along
to the file as eight bytes, high byte first.- Specified by:
writeLong
in interfaceDataOutput
- Parameters:
v
- along
to be written.- Throws:
IOException
- if an I/O error occurs.
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writeFloat
Converts the float argument to anint
using thefloatToIntBits
method in classFloat
, and then writes thatint
value to the file as a 4-byte quantity, high byte first.- Specified by:
writeFloat
in interfaceDataOutput
- Parameters:
v
- afloat
value to be written.- Throws:
IOException
- if an I/O error occurs.- See Also:
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writeDouble
Converts the double argument to along
using thedoubleToLongBits
method in classDouble
, and then writes thatlong
value to the file as an 8-byte quantity, high byte first.- Specified by:
writeDouble
in interfaceDataOutput
- Parameters:
v
- adouble
value to be written.- Throws:
IOException
- if an I/O error occurs.- See Also:
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writeBytes
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.- Specified by:
writeBytes
in interfaceDataOutput
- Parameters:
s
- a string of bytes to be written.- Throws:
IOException
- if an I/O error occurs.
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writeChars
Writes a string to the file as a sequence of characters. Each character is written to the data output stream as if by thewriteChar
method.- Specified by:
writeChars
in interfaceDataOutput
- Parameters:
s
- aString
value to be written.- Throws:
IOException
- if an I/O error occurs.- See Also:
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writeUTF
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.- Specified by:
writeUTF
in interfaceDataOutput
- Parameters:
str
- a string to be written.- Throws:
IOException
- if an I/O error occurs.
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