Create only one object for a class and reuse same object

Question

I want to create only one object of an class and reuse the same object over and over again. Is there any efficient way to do this.

How can I do this?

Answer 1

public final class MySingleton {
    private static volatile MySingleton instance;

    private MySingleton() {
        // TODO: Initialize
        // ...
    }

    /**
      * Get the only instance of this class.
      *
      * @return the single instance.
      */
    public static MySingleton getInstance() {
        if (instance == null) {
            synchronized (MySingleton.class) {
                if (instance == null) {
                    instance = new MySingleton();
                }
            }
        }
        return instance;
    }
}

Answer 2

This is generally implemented with the Singleton pattern but the situations where it is actually required are quite rare and this is not an innocuous decision.

You should consider alternative solutions before making a decision.

This other post about why static variables can be evil is also an interesting read (a singleton is a static variable).