Singleton

Singleton is a simple object-oriented design pattern where a class only gets to have one single instance at any given time while providing a global point of access.

Intent

• Ensures that only one instance of class is exists at a given time.
• Provides a global point of access to the instance.

Here is how you create a singleton:

    class SampleSingleton{
    	
    	private static SampleSingleton instance;
    
    	private SampleSingleton(){
    		// initiate components
    	}
    
    	// This is the global access point
    	public synchronized SampleSingleton getInstance(){
    		if(instance == null){
    			instance = new SampleSingleton();
    		}
    		return instance;
    	}
    
    	public void foreverAlone(){
    		// ...
    	}
    }

After doing this all you need to do is:

    	SampleSingleton.getInstance().foreverAlone();

Using singleton is especially useful when handling single resources such as loggers, configurations etc.