我使用了有关单例创建的已发布教程中的概念,但希望得到一些反馈。有首选方法吗?
public class MyDoubleLockSingleton {
private volatile static Object _mySingleton;
//private constructor
private MyDoubleLockSingleton() {
if (_mySingleton == null) {
MyDoubleLockSingleton.getSingleton();
}
}
// double lock singleton approach
public static Object getSingleton() {
synchronized (MyDoubleLockSingleton.class) {
if (_mySingleton == null) {
_mySingleton = new Object();
}
return (Object)_mySingleton;
}
}
}
最佳答案
它看起来更像是这样的:
public class MyDoubleLockSingleton {
private static final Object _lock = new Object(); // synchronize on this instead of MyDoubleLockSingleton.class
private volatile static MyDoubleLockSingleton _mySingleton;
//private constructor
private MyDoubleLockSingleton() {
// perform expensive initialization here.
}
// double lock singleton approach
public static MyDoubleLockSingleton getSingleton() {
if (_mySingleton == null) {
synchronized (_lock) {
if (_mySingleton == null) {
_mySingleton = new Object();
}
}
}
return _mySingleton;
}
}
- 私有(private)构造函数是您执行昂贵的初始化的地方。
- 您最好在私有(private)成员上进行同步。
- 并且您可能希望在同步块(synchronized block)外部添加空检查以提高性能。否则,这种模式就没有多大意义。
现在,如果您的私有(private)构造函数的代码不是那么昂贵,那么尝试执行延迟初始化确实没有任何意义。在这种情况下,请保持非常简单,如下所示:
public class MyDoubleLockSingleton {
private static final MyDoubleLockSingleton _mySingleton = new MyDoubleLockSingleton();
//private constructor
private MyDoubleLockSingleton() {
// perform initialization here.
}
// double lock singleton approach
public static Object getSingleton() {
return _mySingleton;
}
}
关于java - Java 中的 Singleton 类可以接受吗?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31224751/