Singleton : Singleton Pattern « Design Pattern « Java






  1. Java
  2. Design Pattern
  3. Singleton Pattern

Singleton


/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
/** An example of a Singleton implementation in Java.
 * The Singleton design pattern is described in GOF; the idea is to ensure
 * that only one instance of the class will exist in a given application.
 * @author Ian F. Darwin, http://www.darwinsys.com/
 * @version $Id: Singleton.java,v 1.7 2004/02/09 03:33:58 ian Exp $
 */
public class Singleton {

  private static Singleton singleton = new Singleton();

  /** A private Constructor prevents any other class from instantiating. */
  private Singleton() {
  }

  /** Static 'instance' method */
  public static Singleton getInstance() {
    return singleton;
  }

  // other methods protected by singleton-ness would be here...

  /** A simple demo method */
  public String demoMethod() {
    return "demo";
  }
}








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