jtsingleton.java

来自「Java Pattern Oriented Framework (Jt) 是为了」· Java 代码 · 共 71 行

package Jt;


/**
 * Jt Implementation of the Singleton pattern.
 */

public class JtSingleton extends JtObject {
    
  public static final String JtCLASS_NAME = JtSingleton.class.getName(); 
  private static final long serialVersionUID = 1L;
  private static Object instance;



  public JtSingleton () {
  }

/**
  * Returns the unique class instance.
  */

  public static synchronized Object getInstance()
  {
    return instance;
  }


/**
  * Specifies the unique class instance.
  */

  public static synchronized void setInstance(Object newInstance)
  {
    if (instance == null)
      instance = newInstance;

  }

 
  /**
   * Demonstrates the messages processed by JtSingleton.
   */

  public static void main(String[] args) {

    JtFactory main = new JtFactory ();
    JtSingleton singleton, singleton1;

    System.out.println ("Creating an instance of a singleton ...");

    // Create a JtSingleton instance

    singleton = (JtSingleton) main.createObject (JtSingleton.JtCLASS_NAME, "singleton");


    System.out.println ("Attempting to create a second instance of a singleton ...");

    singleton1 = (JtSingleton) main.createObject (JtSingleton.JtCLASS_NAME, "singleton1");

    main.removeObject (singleton);


  }

}