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Thread: Optimizing Singleton Design Pattern

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    Default Optimizing Singleton Design Pattern

    Hi,

    Given a singleton class, if too many threads start accessing the class, the performance will get hampered. SO how do we optimize the code for this?


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    Super Moderator helloworld922's Avatar
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    Default Re: Optimizing Singleton Design Pattern

    If you're not modifying the singleton (either externally or internally) then theoretically every thread can access the singleton mutually with no negative effects.

    If you're able to partition the singleton into "sections" (for example, you have a 2D array and each thread operates on only a small block of the array), then again you can safely access the singleton without requiring synchronization.

    If your threads require a complete lock on the singleton (or a partial lock that all threads need), then there's no optimization which can take place because at most only 1 thread can safely access the singleton. This is a design bottleneck and no amount of optimization can fix this. The only option is to redesign your application to avoid this case.

    Without a more specific example (aka code) it's difficult to determine how to get more performance out of your code, or if this is even required.

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    Default Re: Optimizing Singleton Design Pattern

    Here is my singletonclss code
    class SingletonClass {
     
    	private static SingletonClass singletonObject;
    	/** A private Constructor prevents any other class from instantiating. */
    	private SingletonClass() {
    		//	 Optional Code
    	}
    	public static synchronized SingletonClass getSingletonObject() {
    		if (singletonObject == null) {
    			singletonObject = new SingletonClass();
    		}
    		return singletonObject;
    	}
    	public Object clone() throws CloneNotSupportedException {
    		throw new CloneNotSupportedException();
    	}
    }
    public class SingletonObjectDemo {
     
    	public static void main(String args[]) {
    		//		SingletonClass obj = new SingletonClass();
                    //Compilation error not allowed
    		SingletonClass obj = SingletonClass.getSingletonObject();
    		// Your Business Logic
    		System.out.println("Singleton object obtained");
    	}
    }
    Last edited by helloworld922; April 18th, 2011 at 07:58 PM.

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    Super Moderator helloworld922's Avatar
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    Default Re: Optimizing Singleton Design Pattern

    On thing I can see right away is to get rid of the synchronization, as well as immediately initializing the singleton object (use a static initializer block, or just initialize it when you declare it). You're getter method can then simply return the singleton object without checking to see if it's null and creating the singleton object. This will allow multiple threads to retrieve the singleton object at the same time. However, there's no way for me to know how you're using that object which would say whether you can safely use that object in multiple threads at the same time.

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    Super Moderator Json's Avatar
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    Default Re: Optimizing Singleton Design Pattern

    I would agree with removing the synchronized keyword and rather instantiate your singleton directly at the static declaration.

    You should really try to avoid using synchronized if there is no need as it just complicates the code but it's not always possible to do that.

    If you leave the code as it is, it will be efficient enough, the getSingletonObject method does not really impose a high performance risk since all it does is return a value.

    I myself prefer to use Google Guice these days so I don't see these issues, I never really need to call new on any class except for the odd rare occasion

  6. The Following User Says Thank You to Json For This Useful Post:

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