单例设计模式之安全的懒汉式

package 单例模式;
/**
 * 单例设计模式之安全的懒汉式
 */
class Single{
	private static Single single= null;
	//私有构造方法
	private Single() {
	}
	//对外提供公有的获取内部创建的Single对象
	public static Single getInstance(){
		if(single==null)
		{
			synchronized(Single.class)
			{
				if(single==null)
				{
					single = new Single();
				}
			}
		}
		return single;
	}
}

public class Test {
	public static void main(String[] args) {
		Single s1 = Single.getInstance();
		Single s2 = Single.getInstance();
		System.out.println(s1);
		System.out.println(s2);
		System.out.println("==比較s1和s2两个对象:"+(s1==s2));
		System.out.println("equals比較s1和s2两个对象:"+(s1.equals(s2)));
	}
}