Singleton Pattern - Example of Use With The Factory Method Pattern

Example of Use With The Factory Method Pattern

The singleton pattern is often used in conjunction with the factory method pattern to create a system-wide resource whose specific type is not known to the code that uses it. An example of using these two patterns together is the Java Abstract Window Toolkit (AWT).

java.awt.Toolkit is an abstract class that binds the various AWT components to particular native toolkit implementations. The Toolkit class has a Toolkit.getDefaultToolkit factory method that returns the platform-specific subclass of Toolkit. The Toolkit object is a singleton because the AWT needs only a single object to perform the binding and the object is relatively expensive to create. The toolkit methods must be implemented in an object and not as static methods of a class because the specific implementation is not known by the platform-independent components. The name of the specific Toolkit subclass used is specified by the "awt.toolkit" environment property accessed through System.getProperties.

The binding performed by the toolkit allows, for example, the backing implementation of a java.awt.Window to bind to the platform-specific java.awt.peer.WindowPeer implementation. Neither the Window class nor the application using the window needs to be aware of which platform-specific subclass of the peer is used.

Read more about this topic:  Singleton Pattern

Famous quotes containing the words factory, method and/or pattern:

    Baltimore lay very near the immense protein factory of Chesapeake Bay, and out of the bay it ate divinely. I well recall the time when prime hard crabs of the channel species, blue in color, at least eight inches in length along the shell, and with snow-white meat almost as firm as soap, were hawked in Hollins Street of Summer mornings at ten cents a dozen.
    —H.L. (Henry Lewis)

    Too poor for a bribe, and too proud to importune,
    He had not the method of making a fortune.
    Thomas Gray (1716–1771)

    Art is the imposing of a pattern on experience, and our aesthetic enjoyment is recognition of the pattern.
    Alfred North Whitehead (1861–1947)