登记式单例模式

package comhellojava;

import java.util.HashMap;
import java.util.Map;

/**
 * @function 登记式单例模式  类似于spring里面的用法，将类名注册，下次从里面直接获取
 * @author ylchou
 * @time 2012/08/28
 *
 */
public class Singleton {
    
    private static Map<String, Singleton> map = new HashMap<String,Singleton>();
    static{
        Singleton singleton = new Singleton();
        System.out.println("--------"+singleton.getClass().getName());
        
        //把singleton实例 put 进 comhellojava.Singleton
        map.put(singleton.getClass().getName(), singleton);
    }
    
    //protected 构造器
//    protected Singleton(){
//    }
    
    private Singleton(){
    }
    
    //静态工厂方法 返回此类唯一的实例
    public static Singleton getInstance(String name){
        if(name == null){
            name = Singleton.class.getName();
            System.out.println("if name is null,->name=" + name);
        }
        
        if(map.get(name) == null){
            try {
                map.put(name, (Singleton) Class.forName(name).newInstance());
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
        return map.get(name);
    }
    
    public String about() {
        return "登记式单例模式";
    }

    public static void main(String[] args) {
        Singleton s = Singleton.getInstance(null);
        Singleton s2 = Singleton.getInstance(null);
        System.out.println(s);
        System.out.println(s2);
        System.out.println(s.about());
    }
}

/**
--------comhellojava.Singleton
if name is null,->name=comhellojava.Singleton
if name is null,->name=comhellojava.Singleton
comhellojava.Singleton@de6ced
comhellojava.Singleton@de6ced
登记式单例模式
 */