Java之创建对象>3.Enforce the singleton property with a private constructor or an enum type详解编程语言

The main advantage of the public field approach is that the declarations make it clear that the class is a singleton: the public static field is final, so it will always contain the same object reference. There is no longer any performance advantage to the public field approach (没有任何性能优势)

 

// Singleton with static factory 

public class Elvis { 

 private static final Elvis INSTANCE = new Elvis(); 

 private Elvis() { ... } 

 public static Elvis getInstance() { return INSTANCE; } 

 public void leaveTheBuilding() { ... } 

}

One advantage of the factory-method approach is that it gives you the flexibility to change your mind about whether the class should be a singleton without changing its API. The factory method returns the sole instance but could easily be modified to return, say, a unique instance for each thread that invokes it. A second advantage, concerning generic types. Often neither of these advantages is relevant, and the final-field approach is simpler.

// Enum singleton - the preferred approach 

public enum Elvis { 

 INSTANCE; 

 public void leaveTheBuilding() { ... } 

}

 While this approach has yet to be widely adopted, a single-element enum type is the best way to implement a singleton.

原创文章，作者：Maggie-Hunter，如若转载，请注明出处：https://blog.ytso.com/15971.html