Tells whether or not this buffer's content is resident in physical
memory.
A return value of true implies that it is highly likely
that all of the data in this buffer is resident in physical memory and
may therefore be accessed without incurring any virtual-memory page
faults or I/O operations. A return value of false does not
necessarily imply that the buffer's content is not resident in physical
memory.
The returned value is a hint, rather than a guarantee, because the
underlying operating system may have paged out some of the buffer's data
by the time that an invocation of this method returns.
Returns:
true if it is likely that this buffer's content
is resident in physical memory