BE THE CODER > Design Patterns > Java Design Patterns

This example shows creating a registry singleton. It helps to have module specific singletons.

File Name :	com/bethecoder/tutorials/dp/singleton/registry/RegistrySingleton.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.dp.singleton.registry;



import java.util.HashMap;

import java.util.Map;



public class RegistrySingleton {



  private static Map<String, RegistrySingleton> registry = new HashMap<String, RegistrySingleton>();

  private String moduleName = null;



  /**

   * Make sure to have private default constructor.

   * This avoids direct instantiation of class using 

   * new keyword/Class.newInstance() method

   */

  private RegistrySingleton() {

  }

  

  public static synchronized RegistrySingleton getInstance(String moduleName) {

    

    RegistrySingleton instance = null;

    

    if (registry.containsKey(moduleName)) {

      instance =  registry.get(moduleName);

    } else {

      instance = new RegistrySingleton();

      instance.moduleName = moduleName;

      registry.put(moduleName, instance);

    }

    

    return instance;

  }

  

  public String getModuleName() {

    return moduleName;

  }



  public String toString() {

    return "RegistrySingletonn : " + getModuleName();

  }



}

File Name :	com/bethecoder/tutorials/dp/singleton/registry/Test.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.dp.singleton.registry;



public class Test {

  

  public static void main (String [] args) {

    

    System.out.println(RegistrySingleton.getInstance("UI"));

    System.out.println(RegistrySingleton.getInstance("Server"));

    System.out.println(RegistrySingleton.getInstance("UI"));

    System.out.println(RegistrySingleton.getInstance("Admin"));

    System.out.println(RegistrySingleton.getInstance("Server"));

    

  }

}

Registry Singleton