单例的最佳实践！！(二)
class loader) than the moment that getInstance() is called. Thus, this solution is thread-safe without requiring special language constructs (i.e. volatile or synchronized).
public class Singleton {
// Private constructor prevents instantiation from other classes
private Singleton() { }
/**
* SingletonHolder is loaded on the first execution of Singleton.getInstance()
*/
private static class SingletonHolder {
public static final Singleton INSTANCE = new Singleton();
}
public static Singleton getInstance() {
return SingletonHolder.INSTANCE;
}
}