对单例模式的改进

给出一种对单例模式改进

package boke.mode;

package boke.mode;

/**
 * 单例模式改进
 * 
 * @since jdk1.6
 * @author 毛正吉
 * @version 1.0
 * @date 2010.06.08
 * 
 */
public class Singleton {
	
	/**
	 * 
	 * @param args
	 */
	public static void main(String[] args) {
		Singleton s1 = Singleton.getInstance();
		Singleton s2 = Singleton.getInstance();
		Singleton s3 = Singleton.getInstance();
		Singleton s4 = Singleton.getInstance();
		Singleton s5 = Singleton.getInstance();

		System.out.println(s1 == s2);
		System.out.println(s2 == s3);
		System.out.println(s3 == s4);
		System.out.println(s4 == s5);
	}

	/**
	 * 私有内部类
	 * @author 毛正吉
	 *
	 */
	private static class SingletonCreate {
		private static final Singleton instance = new Singleton();
	}
	
	/**
	 * 私有构造
	 */
	private Singleton() {
		System.out.println("Singleton Constructor...");
	}

	public static final Singleton getInstance() {

		return SingletonCreate.instance;

	}
}