Multiple instances of class with static constructor

Question

I have existing design of sort of "singleton" implementation with static constructor. I want to be able to destroy and recreate new instance.

Can this be done without changing the base design?

This is simplified prototype:

public static void main(String[] args) { ClassA.doWork(); ClassA.destruct(); ClassA.doWork(); // <--I need new instance here } public class ClassA { private static ClassA inst = new ClassA(); protected ClassA() { //init } public static void doWork(){ //do work } public static void destruct(){ inst = null; } }

You might do the inst = new ClassA() in your doWork() method if you need a new instance EVERYTIME you call that method. — Marc
– Marc, Commented Feb 4, 2013 at 11:09
Can this be done without changing the base design? Probably. Should I keep the base design? Probably not. — assylias
– assylias, Commented Feb 4, 2013 at 11:11
not every time, only when the instance is explicitly destroyed — yuris
– yuris, Commented Feb 4, 2013 at 11:13

David Lavender · Accepted Answer · 2013-02-04 11:19:32Z

If you're determined to go down this route, and don't like the null checks on every method, you could change your "destruct" approach to "reset":

 public static void reset(){ inst = new ClassA(); }

Call that instead of destruct.

But, seriously, don't do it... spend time now to refactor this mess or it'll come back to bite you!

Azodious · Accepted Answer · 2013-02-04 11:11:11Z

Add following code to doWork Method:

public static void doWork() { if(inst == null) { inst = new ClassA(); } //do work }

OR

Add a separate method to create instance, (similar to how you have to destory)

public static ClassA init() { if(inst == null) { inst = new ClassA(); } return inst; }

the problem with that, that I have more then one doWork() methods, i will have to add this section to every one of them.

orique · Accepted Answer · 2013-02-04 11:11:39Z

The method doWork should check against null instances and either throw an IllegalStateException or create a new instance of ClassA and then do the logic:

 public static void doWork(){ if (inst == null){ // throw new IllegalStateException("instance has been destroyed"); // or inst = new ClassA(); } // doWork now }

CloudyMarble · Accepted Answer · 2013-02-04 11:30:47Z

Create an instance in the doWork method like:

 private static ClassA inst; public static void doWork() { if (inst == null) { inst = new ClassA(); } }

Collectives™ on Stack Overflow

Multiple instances of class with static constructor

4 Answers 4

Comments

2 Comments

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

2 Comments

Comments

Comments

Related