Java in a Nutshell, 5th Edition

Name

Buffer

Synopsis

This class is the abstract superclass of all buffer classes in the java.nio API. A buffer is a linear (finite) sequence of prmitive values. The java.nio package defines a Buffer subclass for each primitive type in Java except for boolean. Buffer itself defines the common, type-independent features of all buffers. Buffer and its subclasses are intended for use by a single thread at a time, and contain no synchronization code to make them thread-safe.

The purpose of a buffer is to store data, and buffer classes must define methods for reading data from a buffer and writing data into a buffer. Because each Buffer subclass stores data of a different primitive type, however, the get( ) and put( ) methods that read and write data must be defined by each of the individual subclasses. See ByteBuffer (the most important subclass) for documentation of these methods; all the other subclasses define similar methods which differ only in the datatype of the values being read or written.

Each buffer has four numbers associated with it:

capacity

A buffer’s capacity is its maximum size; it can hold this many values. The capacity is specified when a buffer is created, and may not be changed; it can be queried with the capacity( ) method.

limit

A buffer’s limit is its current size, or the index of the first element that does not contain valid data. Data cannot be read from or written into a buffer beyond the limit. When data is being written into a buffer, the limit is usually the ...