Class RandomAccessFile

java.lang.Object
java.io.RandomAccessFile
All Implemented Interfaces:
Closeable,DataInput,DataOutput,AutoCloseable
public classRandomAccessFileextendsObjectimplementsDataOutput,DataInput,Closeable
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 thefile 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 thegetFilePointer method and set by theseek 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, anEOFException (which is a kind ofIOException) is thrown. If any byte cannot be read for any reason other than end-of-file, anIOException other thanEOFException is thrown. In particular, anIOException may be thrown if the stream has been closed.

Since:
1.0

  • Constructor Summary

    Constructors
    Constructor
    Description
    Creates a random access file stream to read from, and optionally to write to, the file specified by theFile argument.
    RandomAccessFile(String pathname,String mode)
    Creates a random access file stream to read from, and optionally to write to, a file with the specified pathname.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Closes this random access file stream and releases any system resources associated with the stream.
    Returns the uniqueFileChannel object associated with this file.
    Returns the opaque file descriptor object associated with this stream.
    long
    Returns the current offset in this file.
    long
    Returns the length of this file.
    int
    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
    Reads a signed eight-bit value from this file.
    final char
    Reads a 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, starting at the current file pointer.
    final void
    readFully(byte[] b, int off, int len)
    Reads exactlylen bytes from this file into the byte array, starting at the current file pointer.
    final int
    Reads a signed 32-bit integer from this file.
    finalString
    Reads the next line of text from this file.
    final long
    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 eight-bit number from this file.
    final int
    Reads an unsigned 16-bit number from this file.
    finalString
    Reads in a string from this file.
    void
    seek(long pos)
    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 overn bytes of input discarding the skipped bytes.
    void
    write(byte[] b)
    Writesb.length bytes from the specified byte array to this file, starting at the current file pointer.
    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 one-byte value.
    final void
    writeByte(int v)
    Writes abyte to the file as a one-byte value.
    final void
    Writes the string to the file as a sequence of bytes.
    final void
    writeChar(int v)
    Writes achar to the file as a two-byte value, high byte first.
    final void
    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 eight-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 four-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 usingmodified UTF-8 encoding in a machine-independent manner.

  • Constructor Details

    • RandomAccessFile

      public RandomAccessFile(String pathname,String mode) throwsFileNotFoundException
      Creates a random access file stream to read from, and optionally to write to, a file with the specified pathname. If the file exists it is opened; if it does not exist and write mode is specified, a new file is created.Symbolic links are automatically redirected to thetarget of the link. A newFileDescriptor object is created to represent the connection to the file.

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

      Parameters:
      pathname - the system-dependent pathname string
      mode - the accessmode
      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 pathname string does not denote an existing regular file, or if the mode begins with"rw" but the given pathname string does not denote an existing, writable regular file and a new regular file of that pathname cannot be created, or if some other error occurs while opening or creating the file

    • RandomAccessFile

      public RandomAccessFile(File file,String mode) throwsFileNotFoundException
      Creates a random access file stream to read from, and optionally to write to, the file specified by theFile argument. If the file exists it is opened; if it does not exist and write mode is specified, a new file is created.Symbolic links are automatically redirected to thetarget of the link. A newFileDescriptor object is created to represent the connection to the file.

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

      Access mode permitted values and meanings
      ValueMeaning
      "r" Open for reading only. Invoking any of thewrite methods of the resulting object will cause anIOException 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 theforce(boolean) method of theFileChannel class, passing arguments oftrue andfalse, 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.

      Parameters:
      file - the file object
      mode - the access mode, as describedabove
      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 pathname cannot be created, or if some other error occurs while opening or creating the file
      See Also:

  • Method Details

    • getFD

      public final FileDescriptor getFD() throwsIOException
      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:

    • getChannel

      public final FileChannel getChannel()
      Returns the uniqueFileChannel object associated with this file.

      Theposition of the returned channel will always be equal to this object's file-pointer offset as returned by thegetFilePointer 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:
      the file channel associated with this file
      Since:
      1.4

    • read

      public int read() throwsIOException
      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.

      AlthoughRandomAccessFile is not a subclass ofInputStream, this method behaves in exactly the same way as theInputStream.read() method ofInputStream.

      Returns:
      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

      public int read(byte[] b, int off, int len) throwsIOException
      Reads up tolen bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

      AlthoughRandomAccessFile is not a subclass ofInputStream, this method behaves in exactly the same way as theInputStream.read(byte[], int, int) method ofInputStream.

      Parameters:
      b - the buffer into which the data is read.
      off - the start offset in arrayb at which the data is written.
      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 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 - Ifb isnull.
      IndexOutOfBoundsException - Ifoff is negative,len is negative, orlen is greater thanb.length - off

    • read

      public int read(byte[] b) throwsIOException
      Reads up tob.length bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

      AlthoughRandomAccessFile is not a subclass ofInputStream, this method behaves in exactly the same way as theInputStream.read(byte[]) method ofInputStream.

      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 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 - Ifb isnull.

    • readFully

      public final void readFully(byte[] b) throwsIOException
      Readsb.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.
      Specified by:
      readFully in interface DataInput
      Parameters:
      b - the buffer into which the data is read.
      Throws:
      NullPointerException - ifb isnull.
      EOFException - if this file reaches the end before reading all the bytes.
      IOException - if an I/O error occurs.

    • readFully

      public final void readFully(byte[] b, int off, int len) throwsIOException
      Reads exactlylen 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.
      Specified by:
      readFully in interface DataInput
      Parameters:
      b - the buffer into which the data is read.
      off - the start offset into the data arrayb.
      len - the number of bytes to read.
      Throws:
      NullPointerException - ifb isnull.
      IndexOutOfBoundsException - ifoff is negative,len is negative, orlen is greater thanb.length - off.
      EOFException - if this file reaches the end before reading all the bytes.
      IOException - if an I/O error occurs.

    • skipBytes

      public int skipBytes(int n) throwsIOException
      Attempts to skip overn 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 beforen bytes have been skipped is only one possibility. This method never throws anEOFException. The actual number of bytes skipped is returned. Ifn is negative, no 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 an I/O error occurs.

    • write

      public void write(int b) throwsIOException
      Writes the specified byte to this file. The write starts at the current file pointer.
      Specified by:
      write in interface DataOutput
      Parameters:
      b - thebyte to be written.
      Throws:
      IOException - if an I/O error occurs.

    • write

      public void write(byte[] b) throwsIOException
      Writesb.length bytes from the specified byte array to this file, starting at the current file pointer.
      Specified by:
      write in interface DataOutput
      Parameters:
      b - the data.
      Throws:
      IOException - if an I/O error occurs.

    • write

      public void write(byte[] b, int off, int len) throwsIOException
      Writeslen bytes from the specified byte array starting at offsetoff to this file.
      Specified by:
      write in interface DataOutput
      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.
      IndexOutOfBoundsException - Ifoff is negative,len is negative, orlen is greater thanb.length - off

    • getFilePointer

      public long getFilePointer() throwsIOException
      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.

    • seek

      public void seek(long pos) throwsIOException
      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:
      pos - the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.
      Throws:
      IOException - ifpos is less than0 or if an I/O error occurs.

    • length

      public long length() throwsIOException
      Returns the length of this file.
      Returns:
      the length of this file, measured in bytes.
      Throws:
      IOException - if an I/O error occurs.

    • setLength

      public void setLength(long newLength) throwsIOException
      Sets the length of this file.

      If the present length of the file as returned by thelength method is greater than the desired length of the file specified by thenewLength argument, then the file will be truncated.

      If the present length of the file is smaller than the desired length, then the file will be extended. The contents of the extended portion of the file are not defined.

      If the present length of the file is equal to the desired length, then the file and its length will be unchanged.

      In all cases, after this method returns, the file offset as returned by thegetFilePointer method will equal the minimum of the desired length and the file offset before this method was called, even if the length is unchanged. In other words, this method constrains the file offset to the closed interval[0,newLength].

      Parameters:
      newLength - The desired length of the file
      Throws:
      IOException - If the argument is negative or if some other I/O error occurs
      Since:
      1.2

    • close

      public void close() throwsIOException
      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.

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      API Note:
      If this stream has an associated channel then this method will close the channel, which in turn will close this stream. Subclasses that override this method should be prepared to handle possible reentrant invocation.
      Throws:
      IOException - if an I/O error occurs.

    • readBoolean

      public final boolean readBoolean() throwsIOException
      Reads aboolean from this file. This method reads a single byte from the file, starting at the current file pointer. 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 interface DataInput
      Returns:
      theboolean value read.
      Throws:
      EOFException - if this file has reached the end.
      IOException - if an I/O error occurs.

    • readByte

      public final byte readByte() throwsIOException
      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 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 interface DataInput
      Returns:
      the next byte of this file as a signed eight-bitbyte.
      Throws:
      EOFException - if this file has reached the end.
      IOException - if an I/O error occurs.

    • readUnsignedByte

      public final int readUnsignedByte() throwsIOException
      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.

      Specified by:
      readUnsignedByte in interface DataInput
      Returns:
      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.

    • readShort

      public final short readShort() throwsIOException
      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, 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 interface DataInput
      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.

    • readUnsignedShort

      public final int readUnsignedShort() throwsIOException
      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, 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 interface DataInput
      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.

    • readChar

      public final char readChar() throwsIOException
      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, 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 interface DataInput
      Returns:
      the next two bytes of this file, interpreted as achar.
      Throws:
      EOFException - if this file reaches the end before reading two bytes.
      IOException - if an I/O error occurs.

    • readInt

      public final int readInt() throwsIOException
      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, 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 interface DataInput
      Returns:
      the next four bytes of this file, interpreted as anint.
      Throws:
      EOFException - if this file reaches the end before reading four bytes.
      IOException - if an I/O error occurs.

    • readLong

      public final long readLong() throwsIOException
      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, 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 interface DataInput
      Returns:
      the next eight bytes of this file, interpreted as along.
      Throws:
      EOFException - if this file reaches the end before reading eight bytes.
      IOException - if an I/O error occurs.

    • readFloat

      public final float readFloat() throwsIOException
      Reads afloat from this file. This method reads anint value, starting at the current file pointer, 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 interface DataInput
      Returns:
      the next four bytes of this file, interpreted as afloat.
      Throws:
      EOFException - if this file reaches the end before reading four bytes.
      IOException - if an I/O error occurs.
      See Also:

    • readDouble

      public final double readDouble() throwsIOException
      Reads adouble from this file. This method reads along value, starting at the current file pointer, 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 interface DataInput
      Returns:
      the next eight bytes of this file, interpreted as adouble.
      Throws:
      EOFException - if this file reaches the end before reading eight bytes.
      IOException - if an I/O error occurs.
      See Also:

    • readLine

      public final String readLine() throwsIOException
      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.

      Specified by:
      readLine in interface DataInput
      Returns:
      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.

    • readUTF

      public final String readUTF() throwsIOException
      Reads in a string from this file. The string has been encoded using amodified UTF-8 format.

      The first two bytes are read, starting from the current file pointer, as if byreadUnsignedShort. 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.

      Specified by:
      readUTF in interface DataInput
      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 modified UTF-8 encoding of a Unicode string.
      See Also:

    • writeBoolean

      public final void writeBoolean(boolean v) throwsIOException
      Writes aboolean to the file as a one-byte value. The valuetrue is written out as the value(byte)1; the valuefalse is written out as the value(byte)0. The write starts at the current position of the file pointer.
      Specified by:
      writeBoolean in interface DataOutput
      Parameters:
      v - aboolean value to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeByte

      public final void writeByte(int v) throwsIOException
      Writes abyte to the file as a one-byte value. The write starts at the current position of the file pointer.
      Specified by:
      writeByte in interface DataOutput
      Parameters:
      v - abyte value to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeShort

      public final void writeShort(int v) throwsIOException
      Writes ashort to the file as two bytes, high byte first. The write starts at the current position of the file pointer.
      Specified by:
      writeShort in interface DataOutput
      Parameters:
      v - ashort to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeChar

      public final void writeChar(int v) throwsIOException
      Writes achar to the file as a two-byte value, high byte first. The write starts at the current position of the file pointer.
      Specified by:
      writeChar in interface DataOutput
      Parameters:
      v - achar value to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeInt

      public final void writeInt(int v) throwsIOException
      Writes anint to the file as four bytes, high byte first. The write starts at the current position of the file pointer.
      Specified by:
      writeInt in interface DataOutput
      Parameters:
      v - anint to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeLong

      public final void writeLong(long v) throwsIOException
      Writes along to the file as eight bytes, high byte first. The write starts at the current position of the file pointer.
      Specified by:
      writeLong in interface DataOutput
      Parameters:
      v - along to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeFloat

      public final void writeFloat(float v) throwsIOException
      Converts the float argument to anint using thefloatToIntBits method in classFloat, and then writes thatint value to the file as a four-byte quantity, high byte first. The write starts at the current position of the file pointer.
      Specified by:
      writeFloat in interface DataOutput
      Parameters:
      v - afloat value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:

    • writeDouble

      public final void writeDouble(double v) throwsIOException
      Converts the double argument to along using thedoubleToLongBits method in classDouble, and then writes thatlong value to the file as an eight-byte quantity, high byte first. The write starts at the current position of the file pointer.
      Specified by:
      writeDouble in interface DataOutput
      Parameters:
      v - adouble value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:

    • writeBytes

      public final void writeBytes(String s) throwsIOException
      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.
      Specified by:
      writeBytes in interface DataOutput
      Parameters:
      s - a string of bytes to be written.
      Throws:
      IOException - if an I/O error occurs.

    • writeChars

      public final void writeChars(String s) throwsIOException
      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. The write starts at the current position of the file pointer.
      Specified by:
      writeChars in interface DataOutput
      Parameters:
      s - aString value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:

    • writeUTF

      public final void writeUTF(String str) throwsIOException
      Writes a string to the file usingmodified 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 thewriteShort 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.

      Specified by:
      writeUTF in interface DataOutput
      Parameters:
      str - a string to be written.
      Throws:
      IOException - if an I/O error occurs.