为了安全,加上synchronized (Singleton5.class)同步监视器已经解决了,外面加上一层if判断是为了性能问题,如果有实例了就不等待锁了。 第六种:静态内部类 package org.example.singleton;/** * 静态内部类:我们就不用一个静态变量去保存这个实例了,我们用一个内部类去存储实例。 * 延迟创建实例:在当内部类被加载...
So the way to resolve the problem is to have a second verification in the synchronized block. There is an idiom that does this verification:double-checked locking. Double-Checked Locking Singleton Listing 4 shows a singleton class declaration with double-checked locking. public class JavaSingleton ...
2.2double checked locking Copy publicclassSingleton{privatestaticvolatileSingletoninstance=null;// Private constructor suppresses// default public constructorprivateSingleton(){};//Thread safe and performance promotepublicstaticSingletongetInstance(){if(instance ==null){synchronized(Singleton.class){// When mor...
is not a very good candidate to be used with synchronized keyword. It’s because they are stored in astring pooland we don’t want to lock a string that might be getting used by another piece of code. So I am using an Object variable. Learn more about synchronization andthread safety i...
publicclassSingleton{privatestaticSingleton instance;privateSingleton(){}publicstaticsynchronizedSingletongetInstance(){if(instance ==null) { instance =newSingleton(); }returninstance; } } 这种方式能够在多线程中很好的工作,但是每次调用getInstance方法时都需要进行同步,造成不必要的同步开销。
public static synchronized MySingleton getInstance() { if (_instance==null) { _instance = new MySingleton(); } return _instance; } // Remainder of class definition . . . } Both Singleton implementations do not allow convenient subclassing, sincegetInstance(), being static, cannot be overridden...
to learn java. But for someone a bit experienced who will understand what is happening and need a bit more speed, the second implementation is definitely the way to go. Moreover, most of the time when doing multi-threading, it is a good thing to reduce the size of the synchronized code...
Java单例模式实现: public class Scoreboard { public int currentScore; //we will use this for the score later on private static Scoreboard singleton = null; //this we will need for the implementation protected Scoreboard(){ //nothing here really. At least for this example. ...
This error can be solved usingdouble-checked locking. This principle tells us to recheck the instance variable again in asynchronizedblock as given below: publicclassLazySingleton{privatestaticvolatileLazySingletoninstance=null;// private constructorprivateLazySingleton(){}publicstaticLazySingletongetInstance(...
responsible for ensuring that the state of the singleton is synchronized across all clients. Developers who create singletons with bean-managed concurrency are allowed to use the Java programming language synchronization primitives, such assynchronizationandvolatile, to prevent errors during concurrent ...