Interacting with Filesystems - Beginning Java 7 - page 710

Note Operations on a random access file opened in "rwd" or "rws" mode are
slower than these same operations on a random access file opened in "rw" mode.
Theseconstructorsthrow FileNotFoundException when mode is "r" andthe
fileidentifiedby pathname cannotbeopened(itmightnotexistoritmightbeadir-
ectory), or when mode is "rw" and pathname is read-only or a directory.
Thefollowingexampledemonstratesthesecondconstructorbyattemptingtoopenan
existing random access file via the "r" mode string:
RandomAccessFile raf = new RandomAccessFile("employee.dat",
"r");
Arandomaccessfileisassociatedwitha file pointer ,acursorthatidentifiestheloca-
tionofthenextbytetowriteorread.Whenanexistingfileisopened,thefilepointeris
set to its first byte, at offset 0. The file pointer is also set to 0 when the file is created.
Write and read operations start at the file pointer and advance it past the number of
byteswrittenorread.Operationsthatwritepastthecurrentendofthefilecausethefile
to be extended. These operations continue until the file is closed.
RandomAccessFile declaresawidevarietyofmethods.Ipresentarepresentative
sample of these methods in Table 8-6 .