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Added in API level 1

Summary: Ctors | Methods | Protected Methods | Inherited Methods | [Expand All]

RandomAccessFile

public class RandomAccessFile
extends Object implements DataOutput, DataInput, Closeable

java.lang.Object
↳	java.io.RandomAccessFile

Instances of this class support both reading and writing to a random access file. A random access file behaves like a large array of bytes stored in the file system. There is a kind of cursor, or index into the implied array, called the file pointer; input operations read bytes starting at the file pointer and advance the file pointer past the bytes read. If the random access file is created in read/write mode, then output operations are also available; output operations write bytes starting at the file pointer and advance the file pointer past the bytes written. Output operations that write past the current end of the implied array cause the array to be extended. The file pointer can be read by the getFilePointer method and set by the seek method.

It is generally true of all the reading routines in this class that if end-of-file is reached before the desired number of bytes has been read, an EOFException (which is a kind of IOException) is thrown. If any byte cannot be read for any reason other than end-of-file, an IOException other than EOFException is thrown. In particular, an IOException may be thrown if the stream has been closed.

Summary

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

Public methods
`void`	`close()` Closes this random access file stream and releases any system resources associated with the stream.
`final FileChannel`	`getChannel()` Returns the unique `FileChannel` object associated with this file.
`final FileDescriptor`	`getFD()` Returns the opaque file descriptor object associated with this stream.
`long`	`getFilePointer()` 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 to `b.length` bytes of data from this file into an array of bytes.
`int`	`read(byte[] b, int off, int len)` Reads up to `len` bytes of data from this file into an array of bytes.
`final boolean`	`readBoolean()` Reads a `boolean` from this file.
`final byte`	`readByte()` Reads a signed eight-bit value from this file.
`final char`	`readChar()` Reads a character from this file.
`final double`	`readDouble()` Reads a `double` from this file.
`final float`	`readFloat()` Reads a `float` from this file.
`final void`	`readFully(byte[] b)` Reads `b.length` bytes from this file into the byte array, starting at the current file pointer.
`final void`	`readFully(byte[] b, int off, int len)` Reads exactly `len` bytes from this file into the byte array, starting at the current file pointer.
`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`	`readShort()` Reads a signed 16-bit number from this file.
`final String`	`readUTF()` Reads in a string from this file.
`final int`	`readUnsignedByte()` Reads an unsigned eight-bit number from this file.
`final int`	`readUnsignedShort()` Reads an unsigned 16-bit number from this file.
`void`	`seek(long offset)` Sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs.
`void`	`setLength(long newLength)` Sets the length of this file.
`int`	`skipBytes(int n)` Attempts to skip over `n` bytes of input discarding the skipped bytes.
`void`	`write(byte[] b)` Writes `b.length` bytes from the specified byte array to this file, starting at the current file pointer.
`void`	`write(byte[] b, int off, int len)` Writes `len` bytes from the specified byte array starting at offset `off` to this file.
`void`	`write(int b)` Writes the specified byte to this file.
`final void`	`writeBoolean(boolean v)` Writes a `boolean` to the file as a one-byte value.
`final void`	`writeByte(int v)` Writes a `byte` to the file as a one-byte value.
`final void`	`writeBytes(String s)` Writes the string to the file as a sequence of bytes.
`final void`	`writeChar(int v)` Writes a `char` to the file as a two-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 a `long` using the `doubleToLongBits` method in class `Double`, and then writes that `long` value to the file as an eight-byte quantity, high byte first.
`final void`	`writeFloat(float v)` 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 four-byte quantity, high byte first.
`final void`	`writeInt(int v)` Writes an `int` to the file as four bytes, high byte first.
`final void`	`writeLong(long v)` Writes a `long` to the file as eight bytes, high byte first.
`final void`	`writeShort(int v)` Writes a `short` to the file as two bytes, high byte first.
`final void`	`writeUTF(String str)` Writes a string to the file using modified UTF-8 encoding in a machine-independent manner.

Protected methods
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

Inherited methods

From class


  
    java.lang.Object

`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 millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

From interface


  
    java.io.DataOutput

`abstract void`	`write(byte[] b)` Writes to the output stream all the bytes in array `b`.
`abstract void`	`write(byte[] b, int off, int len)` Writes `len` bytes from array `b`, in order, to the output stream.
`abstract void`	`write(int b)` Writes to the output stream the eight low-order bits of the argument `b`.
`abstract void`	`writeBoolean(boolean v)` Writes a `boolean` value to this output stream.
`abstract void`	`writeByte(int v)` Writes to the output stream the eight low- order bits of the argument `v`.
`abstract void`	`writeBytes(String s)` Writes a string to the output stream.
`abstract void`	`writeChar(int v)` Writes a `char` value, which is comprised of two bytes, to the output stream.
`abstract void`	`writeChars(String s)` Writes every character in the string `s`, to the output stream, in order, two bytes per character.
`abstract void`	`writeDouble(double v)` Writes a `double` value, which is comprised of eight bytes, to the output stream.
`abstract void`	`writeFloat(float v)` Writes a `float` value, which is comprised of four bytes, to the output stream.
`abstract void`	`writeInt(int v)` Writes an `int` value, which is comprised of four bytes, to the output stream.
`abstract void`	`writeLong(long v)` Writes a `long` value, which is comprised of eight bytes, to the output stream.
`abstract void`	`writeShort(int v)` Writes two bytes to the output stream to represent the value of the argument.
`abstract void`	`writeUTF(String s)` Writes two bytes of length information to the output stream, followed by the modified UTF-8 representation of every character in the string `s`.

From interface


  
    java.io.DataInput

`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.

From interface


  
    java.io.Closeable

From interface


  
    java.lang.AutoCloseable

Public constructors

RandomAccessFile

Added in API level 1

RandomAccessFile (String name, 
                String mode)

Creates a random access file stream to read from, and optionally to write to, a file with the specified name. A new FileDescriptor object is created to represent the connection to the file.

The mode argument specifies the access mode with which the file is to be opened. The permitted values and their meanings are as specified for the RandomAccessFile(File,String) constructor.

If there is a security manager, its checkRead method is called with the name argument as its argument to see if read access to the file is allowed. If the mode allows writing, the security manager's checkWrite method is also called with the name argument as its argument to see if write access to the file is allowed.

Parameters
`name`	`String`: the system-dependent filename
`mode`	`String`: the access mode

Throws
`IllegalArgumentException`	if the mode argument is not equal to one of `"r"`, `"rw"`, `"rws"`, or `"rwd"`
`FileNotFoundException`	if the mode is `"r"` but the given string does not denote an existing regular file, or if the mode begins with `"rw"` but the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
`SecurityException`	if a security manager exists and its `checkRead` method denies read access to the file or the mode is "rw" and the security manager's `checkWrite` method denies write access to the file

See also:

RandomAccessFile

Added in API level 1

RandomAccessFile (File file, 
                String mode)

Creates a random access file stream to read from, and optionally to write to, the file specified by the File argument. A new FileDescriptor object is created to represent this file connection.

The mode argument specifies the access mode in which the file is to be opened. The permitted values and their meanings are:

Value
Meaning

"r" Open for reading only. Invoking any of the write methods of the resulting object will cause an IOException to be thrown.

"rw" Open for reading and writing. If the file does not already exist then an attempt will be made to create it.

"rws" Open for reading and writing, as with "rw", and also require that every update to the file's content or metadata be written synchronously to the underlying storage device.

"rwd" Open for reading and writing, as with "rw", and also require that every update to the file's content be written synchronously to the underlying storage device.

Value	Meaning
`"r"`	Open for reading only. Invoking any of the `write` methods of the resulting object will cause an `IOException` to be thrown.
`"rw"`	Open for reading and writing. If the file does not already exist then an attempt will be made to create it.
`"rws"`	Open for reading and writing, as with `"rw"`, and also require that every update to the file's content or metadata be written synchronously to the underlying storage device.
`"rwd"`	Open for reading and writing, as with `"rw"`, and also require that every update to the file's content be written synchronously to the underlying storage device.

The "rws" and "rwd" modes work much like the force(boolean) method of the FileChannel class, passing arguments of true and false, respectively, except that they always apply to every I/O operation and are therefore often more efficient. If the file resides on a local storage device then when an invocation of a method of this class returns it is guaranteed that all changes made to the file by that invocation will have been written to that device. This is useful for ensuring that critical information is not lost in the event of a system crash. If the file does not reside on a local device then no such guarantee is made.

The "rwd" mode can be used to reduce the number of I/O operations performed. Using "rwd" only requires updates to the file's content to be written to storage; using "rws" requires updates to both the file's content and its metadata to be written, which generally requires at least one more low-level I/O operation.

If there is a security manager, its checkRead method is called with the pathname of the file argument as its argument to see if read access to the file is allowed. If the mode allows writing, the security manager's checkWrite method is also called with the path argument to see if write access to the file is allowed.

Parameters
`file`	`File`: the file object
`mode`	`String`: the access mode, as described above

Throws
`IllegalArgumentException`	if the mode argument is not equal to one of `"r"`, `"rw"`, `"rws"`, or `"rwd"`
`FileNotFoundException`	if the mode is `"r"` but the given file object does not denote an existing regular file, or if the mode begins with `"rw"` but the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
`SecurityException`	if a security manager exists and its `checkRead` method denies read access to the file or the mode is "rw" and the security manager's `checkWrite` method denies write access to the file

See also:

Public methods

close

Added in API level 1

void close ()

Closes this random access file stream and releases any system resources associated with the stream. A closed random access file cannot perform input or output operations and cannot be reopened.

If this file has an associated channel then the channel is closed as well.

Throws
`IOException`	if an I/O error occurs.

getChannel

Added in API level 1

FileChannel getChannel ()

Returns the unique FileChannel object associated with this file.

The position of the returned channel will always be equal to this object's file-pointer offset as returned by the getFilePointer method. Changing this object's file-pointer offset, whether explicitly or by reading or writing bytes, will change the position of the channel, and vice versa. Changing the file's length via this object will change the length seen via the file channel, and vice versa.

Returns
`FileChannel`	the file channel associated with this file

getFD

Added in API level 1

FileDescriptor getFD ()

Returns the opaque file descriptor object associated with this stream.

Returns
`FileDescriptor`	the file descriptor object associated with this stream.

Throws
`IOException`	if an I/O error occurs.

See also:

FileDescriptor

getFilePointer

Added in API level 1

long getFilePointer ()

Returns the current offset in this file.

Returns
`long`	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.

length

Added in API level 1

long length ()

Returns the length of this file.

Returns
`long`	the length of this file, measured in bytes.

Throws
`IOException`	if an I/O error occurs.

read

Added in API level 1

int read ()

Reads a byte of data from this file. The byte is returned as an integer in the range 0 to 255 (0x00-0x0ff). This method blocks if no input is yet available.

Although RandomAccessFile is not a subclass of InputStream, this method behaves in exactly the same way as the read() method of InputStream.

Returns
`int`	the next byte of data, or `-1` if the end of the file has been reached.

Throws
`IOException`	if an I/O error occurs. Not thrown if end-of-file has been reached.

read

Added in API level 1

int read (byte[] b)

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.

Although RandomAccessFile is not a subclass of InputStream, this method behaves in exactly the same way as the read(byte[]) method of InputStream.

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 this file has been reached.

Throws
`IOException`	If the first byte cannot be read for any reason other than end of file, or if the random access file has been closed, or if some other I/O error occurs.
`NullPointerException`	If `b` is `null`.

read

Added in API level 1

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

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.

Although RandomAccessFile is not a subclass of InputStream, this method behaves in exactly the same way as the read(byte[], int, int) method of InputStream.

Parameters
`b`	`byte`: the buffer into which the data is read.
`off`	`int`: the start offset in array `b` at which the data is written.
`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 file has been reached.

Throws
`IOException`	If the first byte cannot be read for any reason other than end of file, or if the random access file has been closed, or if some other I/O error occurs.
`NullPointerException`	If `b` is `null`.
`IndexOutOfBoundsException`	If `off` is negative, `len` is negative, or `len` is greater than `b.length - off`

readBoolean

Added in API level 1

boolean readBoolean ()

Reads a boolean from this file. This method reads a single byte from the file, starting at the current file pointer. 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
`boolean`	the `boolean` value read.

Throws
`EOFException`	if this file has reached the end.
`IOException`	if an I/O error occurs.

readByte

Added in API level 1

byte readByte ()

Reads a signed eight-bit value from this file. This method reads a byte from the file, starting from the current file pointer. If the byte read is b, where 0 <= 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.

Returns
`byte`	the next byte of this file as a signed eight-bit `byte`.

Throws
`EOFException`	if this file has reached the end.
`IOException`	if an I/O error occurs.

readChar

Added in API level 1

char readChar ()

Reads a character from this file. This method reads two bytes from the file, starting at the current file pointer. If the bytes read, in order, are b1 and b2, where 0 <= 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.

Returns
`char`	the next two bytes of this file, interpreted as a `char`.

Throws
`EOFException`	if this file reaches the end before reading two bytes.
`IOException`	if an I/O error occurs.

readDouble

Added in API level 1

double readDouble ()

Reads a double from this file. This method reads a long value, starting at the current file pointer, 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
`double`	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:

readFloat

Added in API level 1

float readFloat ()

Reads a float from this file. This method reads an int value, starting at the current file pointer, 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
`float`	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:

readInt()
intBitsToFloat(int)

readFully

Added in API level 1

void readFully (byte[] b)

Reads b.length bytes from this file into the byte array, starting at the current file pointer. This method reads repeatedly from the file until the requested number of bytes are read. This method blocks until the requested number of bytes are read, the end of the stream is detected, or an exception is thrown.

Parameters
`b`	`byte`: 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.

readFully

Added in API level 1

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

Reads exactly len bytes from this file into the byte array, starting at the current file pointer. This method reads repeatedly from the file until the requested number of bytes are read. This method blocks until the requested number of bytes are read, the end of the stream is detected, or an exception is thrown.

Parameters
`b`	`byte`: the buffer into which the data is read.
`off`	`int`: the start offset of the data.
`len`	`int`: 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.

readInt

Added in API level 1

int readInt ()

Reads a signed 32-bit integer from this file. This method reads 4 bytes from the file, starting at the current file pointer. 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:

     (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.

Returns
`int`	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.

readLine

Added in API level 1

String readLine ()

Reads the next line of text from this file. This method successively reads bytes from the file, starting at the current file pointer, until it reaches a line terminator or the end of the file. Each byte is converted into a character by taking the byte's value for the lower eight bits of the character and setting the high eight bits of the character to zero. This method does not, therefore, support the full Unicode character set.

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 file. Line-terminating characters are discarded and are not 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 file is reached, or an exception is thrown.

Returns
`String`	the next line of text from this file, or null if end of file is encountered before even one byte is read.

Throws
`IOException`	if an I/O error occurs.

readLong

Added in API level 1

long readLong ()

Reads a signed 64-bit integer from this file. This method reads eight bytes from the file, starting at the current file pointer. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, 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.

Returns
`long`	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.

readShort

Added in API level 1

short readShort ()

Reads a signed 16-bit number from this file. The method reads two bytes from this file, starting at the current file pointer. 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:

     (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.

Returns
`short`	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.

readUTF

Added in API level 1

String 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, starting from the current file pointer, 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 modified 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
`String`	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 modified UTF-8 encoding of a Unicode string.

See also:

readUnsignedShort()

readUnsignedByte

Added in API level 1

int readUnsignedByte ()

Reads an unsigned eight-bit number from this file. This method reads a byte from this file, starting at the current file pointer, 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
`int`	the next byte of this file, interpreted as an unsigned eight-bit number.

Throws
`EOFException`	if this file has reached the end.
`IOException`	if an I/O error occurs.

readUnsignedShort

Added in API level 1

int readUnsignedShort ()

Reads an unsigned 16-bit number from this file. This method reads two bytes from the file, starting at the current file pointer. If the bytes read, in order, are b1 and b2, where 0 <= 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.

Returns
`int`	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.

seek

Added in API level 1

void seek (long offset)

Sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs. The offset may be set beyond the end of the file. Setting the offset beyond the end of the file does not change the file length. The file length will change only by writing after the offset has been set beyond the end of the file.

Parameters
`offset`	`long`: the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.

Throws
`IOException`	if `pos` is less than `0` or if an I/O error occurs.

setLength

Added in API level 1

void setLength (long newLength)

Sets the length of this file.

If the present length of the file as returned by the length method is greater than the newLength argument then the file will be truncated. In this case, if the file offset as returned by the getFilePointer method is greater than newLength then after this method returns the offset will be equal to newLength.

If the present length of the file as returned by the length method is smaller than the newLength argument then the file will be extended. In this case, the contents of the extended portion of the file are not defined.

Parameters
`newLength`	`long`: The desired length of the file

Throws
`IOException`	If an I/O error occurs

skipBytes

Added in API level 1

int skipBytes (int n)

Attempts to skip over n bytes of input discarding the skipped bytes.

This method may skip over some smaller number of bytes, possibly zero. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. This method never throws an EOFException. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

Parameters
`n`	`int`: the number of bytes to be skipped.

Returns
`int`	the actual number of bytes skipped.

Throws
`IOException`	if an I/O error occurs.

write

Added in API level 1

void write (byte[] b)

Writes b.length bytes from the specified byte array to this file, starting at the current file pointer.

Parameters
`b`	`byte`: the data.

Throws
`IOException`	if an I/O error occurs.

write

Added in API level 1

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

Writes len bytes from the specified byte array starting at offset off to this file.

Parameters
`b`	`byte`: the data.
`off`	`int`: the start offset in the data.
`len`	`int`: the number of bytes to write.

Throws
`IOException`	if an I/O error occurs.

write

Added in API level 1

void write (int b)

Writes the specified byte to this file. The write starts at the current file pointer.

Parameters
`b`	`int`: the `byte` to be written.

Throws
`IOException`	if an I/O error occurs.

writeBoolean

Added in API level 1

void writeBoolean (boolean v)

Writes a boolean to the file as a one-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0. The write starts at the current position of the file pointer.

Parameters
`v`	`boolean`: a `boolean` value to be written.

Throws
`IOException`	if an I/O error occurs.

writeByte

Added in API level 1

void writeByte (int v)

Writes a byte to the file as a one-byte value. The write starts at the current position of the file pointer.

Parameters
`v`	`int`: a `byte` value to be written.

Throws
`IOException`	if an I/O error occurs.

writeBytes

Added in API level 1

void writeBytes (String s)

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. The write starts at the current position of the file pointer.

Parameters
`s`	`String`: a string of bytes to be written.

Throws
`IOException`	if an I/O error occurs.

writeChar

Added in API level 1

void writeChar (int v)

Writes a char to the file as a two-byte value, high byte first. The write starts at the current position of the file pointer.

Parameters
`v`	`int`: a `char` value to be written.

Throws
`IOException`	if an I/O error occurs.

writeChars

Added in API level 1

void writeChars (String s)

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. The write starts at the current position of the file pointer.

Parameters
`s`	`String`: a `String` value to be written.

Throws
`IOException`	if an I/O error occurs.

See also:

writeChar(int)

writeDouble

Added in API level 1

void writeDouble (double v)

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 eight-byte quantity, high byte first. The write starts at the current position of the file pointer.

Parameters
`v`	`double`: a `double` value to be written.

Throws
`IOException`	if an I/O error occurs.

See also:

doubleToLongBits(double)

writeFloat

Added in API level 1

void writeFloat (float v)

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 four-byte quantity, high byte first. The write starts at the current position of the file pointer.

Parameters
`v`	`float`: a `float` value to be written.

Throws
`IOException`	if an I/O error occurs.

See also:

floatToIntBits(float)

writeInt

Added in API level 1

void writeInt (int v)

Writes an int to the file as four bytes, high byte first. The write starts at the current position of the file pointer.

Parameters
`v`	`int`: an `int` to be written.

Throws
`IOException`	if an I/O error occurs.

writeLong

Added in API level 1

void writeLong (long v)

Writes a long to the file as eight bytes, high byte first. The write starts at the current position of the file pointer.

Parameters
`v`	`long`: a `long` to be written.

Throws
`IOException`	if an I/O error occurs.

writeShort

Added in API level 1

void writeShort (int v)

Writes a short to the file as two bytes, high byte first. The write starts at the current position of the file pointer.

Parameters
`v`	`int`: a `short` to be written.

Throws
`IOException`	if an I/O error occurs.

writeUTF

Added in API level 1

void writeUTF (String str)

Writes a string to the file using modified UTF-8 encoding in a machine-independent manner.

First, two bytes are written to the file, starting at the current file pointer, 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 modified UTF-8 encoding for each character.

Parameters
`str`	`String`: a string to be written.

Throws
`IOException`	if an I/O error occurs.

Protected methods

finalize

Added in API level 1

void finalize ()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. A subclass overrides the finalize method to dispose of system resources or to perform other cleanup.

The general contract of finalize is that it is invoked if and when the Java^TM virtual machine has determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, except as a result of an action taken by the finalization of some other object or class which is ready to be finalized. The finalize method may take any action, including making this object available again to other threads; the usual purpose of finalize, however, is to perform cleanup actions before the object is irrevocably discarded. For example, the finalize method for an object that represents an input/output connection might perform explicit I/O transactions to break the connection before the object is permanently discarded.

The finalize method of class Object performs no special action; it simply returns normally. Subclasses of Object may override this definition.

The Java programming language does not guarantee which thread will invoke the finalize method for any given object. It is guaranteed, however, that the thread that invokes finalize will not be holding any user-visible synchronization locks when finalize is invoked. If an uncaught exception is thrown by the finalize method, the exception is ignored and finalization of that object terminates.

After the finalize method has been invoked for an object, no further action is taken until the Java virtual machine has again determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, including possible actions by other objects or classes which are ready to be finalized, at which point the object may be discarded.

The finalize method is never invoked more than once by a Java virtual machine for any given object.

Any exception thrown by the finalize method causes the finalization of this object to be halted, but is otherwise ignored.

Throws
`Throwable`