Other Ways of Singleton in Java [duplicate]

by

No, it is not. You didn’t declare myClass private static final, nor the getInstance() is static. The code also doesn’t really compile.

Here’s the Singleton idiom:

public class MyClass {
    private static final MyClass myClass = new MyClass();

    private MyClass() {}

    public static MyClass getInstance() {
        return myClass; 
    }
}

It should be private, so that nobody else can access it directly. It should be static so that there’s only one of it. It should be final so that it cannot be reassigned. You also need to instantiate it directly during declaration so that you don’t need to worry (that much) about threading.

If the loading is expensive and you thus rather prefer lazy loading of the Singleton, then consider the Singleton holder idiom which does initialization on demand instead of during classloading:

public class MyClass {
    private MyClass() {}

    private static class LazyHolder {
        private static final MyClass myClass = new MyClass();
    }

    public static MyClass getInstance() {
        return LazyHolder.myClass;
    }
}

You should however put big question marks whether you need a Singleton or not. Often it’s not needed. Just a static variable, an enum, a factory class and/or dependency injection is often the better choice.

More Related Contents:

  1. What is an efficient way to implement a singleton pattern in Java? [closed]
  2. Singletons vs. Application Context in Android?
  3. Why is volatile used in double checked locking
  4. Implementing Singleton with an Enum (in Java)
  5. Double Checked Locking in Singleton
  6. What’s Alternative to Singleton
  7. Singleton Design Pattern: Pitfalls [closed]
  8. Why implementing a Singleton pattern in Java code is (sometimes) considered an anti-pattern in Java world?
  9. should a db connection be a singleton?
  10. Java Singleton Pattern
  11. Why use a singleton instead of static methods?
  12. When would the garbage collector erase an instance of an object that uses Singleton pattern?
  13. Singleton pattern (Bill Pugh’s solution)
  14. How to create a singleton class
  15. What are static factory methods?
  16. Real World Example of the Strategy Pattern
  17. Using Singleton design pattern for SQLiteDatabase
  18. Singleton with Arguments in Java
  19. Is there a Java equivalent or methodology for the typedef keyword in C++?
  20. Java JSON serialization – best practice
  21. Open Session In View Pattern
  22. Builder Pattern and Inheritance
  23. Is there a recommended way to use the Observer pattern in MVP using GWT?
  24. Why does every object in Java implicitly extend java.lang.Object class?
  25. How thread-safe is enum in java?
  26. Is This Use of the “instanceof” Operator Considered Bad Design?
  27. Why people use message/event buses in their code? [closed]
  28. What is the difference between Factory and Strategy patterns?
  29. What is the difference between a fluent interface and the Builder pattern?
  30. How to hide the internal structure of a Java API to the rest of the world

Leave a Comment