私有静态内部类实现线程安全的单例代码如下:

public class Singleton
{
    //构造器私有化
    private Singleton(){ }
/**
 * <a href="/tag/huoqu/" target="_blank" class="keywords">获取</a>对象实例的静态<a href="/tag/fangfa/" target="_blank" class="keywords">方法</a>
 * @return
 */
public static Singleton getInstance()
{
    return SingletonHolder.instance;        
}

//静态内部类，在第一次被引用时被加载
private static class SingletonHolder
{
    private static Singleton instance = new Singleton();
}

public static void main(String args[])
{
    Singleton instance1 = Singleton.getInstance();
    Singleton instance2 = Singleton.getInstance();
    System.out.println(instance1 == instance2);
}
}