- CRC32 computes a checksum using the CRC-32 algorithm.
- Adler32 computes a checksum using the Adler-32 algorithm.
25.10. javax.* Standard Extensions
Standard extensions are packages or collections of packages that can be downloaded to extend the capabilities
of a particular virtual machine. They will usually have names starting with javax, although future exceptions
may be made. Conversely, packages with javax in the name may become part of the main set of packages
over time. For example, the javax.swing and javax.accessibility packages are part of the main
set. The name indicates that they were at first not part of the main set, but integrated later.
Standard extensions are a mechanism that allows growth in the capabilities of the platform without further
extensions to the core packages required of all virtual machines. New standard extensions can be defined and
made available, but only installed where they are needed. Several standard extensions are defined, and more
are on the way. Listing them all is far outside the scope of this bookyou can find more information on the
Web, especially at http://java.sun.com.
25.11. javax.accessibility Accessibility for GUIs
Graphical user interfaces traditionally assume certain kinds of abilities on the part of the user, such as the
ability to use a mouse or keyboard. These assumptions are a problem for some people. The
javax.accessiblity interfaces and classes provide a way to write interfaces that can use assistive
technologies for input and output, allowing people with different abilities to use the same interfaces. If an
application fully supports the accessibility API, then it should be compatible with, and friendly toward,
assistive technologies such as screen readers and magnifiers.
25.12. javax.naming Directory and Naming Services
This package defines the naming operations of the Java Naming and Directory Interface™ (JNDI), with the
subpackage javax.naming.directory, defining the directory operations. These are designed to be
independent of any specific naming or directory service implementation. Thus a variety of servicesnew,
emerging, and already deployed onescan be accessed in a common way.
A context, represented by the Context interface, consists of a set of name-to-object bindings. Context is
the core interface for looking up, binding, unbinding, and renaming objects, and for creating and destroying
subcontexts. lookup is the most commonly used operation. You supply lookup the name of the object you
want to look up, and it returns the object bound to that name. For example, the following code fragment looks
up a printer and sends a document to the printer object to be printed:
Printer printer = (Printer) ctx.lookup("Duplex");
printer.print(report);
Every naming method in the Context interface has two overloads: one that accepts a Name argument and
one that accepts a string name. Name is an interface that represents a generic namean ordered sequence of
zero or more components. For these methods, you can use Name to represent a composite name
(CompositeName) so that you can use a name that spans multiple namespaces.