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I want to know whats the best practice when it comes to Class Initialization,

I mean should I initialize a Class once Customer c = new Customer(); in the top level, and use it everywhere in the class:

Tools tools = new Tools();
    public boolean doCIdCheck(int cId) {
        final Iterator<Customer> cursor = tools.Customers.iterator();
        while (cursor.hasNext()) {
            if (cursor.next().getCIdCheck(cId)) {
                return true;
            }
        }
        return false;
    }

or should I just use new Customer().checkCId(); where ever I need it:

    public boolean doCIdCheck(int cId) {
        final Iterator<Customer> cursor = new Tools().Customers.iterator();
        while (cursor.hasNext()) {
            if (cursor.next().getCIdCheck(cId)) {
                return true;
            }
        }
        return false;
    }

Or best to have each function/method have its own instance of a class:

    public boolean doCIdCheck(int cId) {
        Tools tools = new Tools();
        final Iterator<Customer> cursor = tools.Customers.iterator();
        while (cursor.hasNext()) {
            if (cursor.next().getCIdCheck(cId)) {
                return true;
            }
        }
        return false;
    }
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3
  • It pretty much depends of what you want to achieve, cause these solutions give you absolutely different effects. Commented Sep 4, 2012 at 7:54
  • Well lets just say.. I have a tools class with a bunch of validation methods most for user input... so say my customer class uses these validations to make sure User Input follows Rules.. so whats best to use: new Tools()._entryStringOnly(); at every place i need to validate. or creating a instance right at the top Tools tools = new Tools(); then use tools._entryStringOnly(); at every place i need to validate. or creating every function/method with its own instance to use in that function/method Commented Sep 4, 2012 at 7:59
  • ok err what I want to know is ... the best practice I already mentioned that ill be needing it in every method() in the class... need to know the side effects like to do with Memory Management / speed etc. Commented Sep 4, 2012 at 8:11

4 Answers 4

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1

From your example, it looks like the best approach would be to declare the shared methods and members of Tools as static instead of creating an instance, and just call them as 

final Iterator<Customer> cursor = Tools.Customers.iterator();

This of course assumes that you don't store data in Tools that could cause conflicts, in that case creating multiple instances is preferred.

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1 Comment

Thanks, i do have that actually.. i only changed the things in the example so you guys got what i wanted all my collections are static and i do use them the exact way you have described.
0

Taking into consideration that you will need that Object in every method of the class and taking into account only memory management and processor consumption then:

1.Option 1 (Keep a global variable accessible everywhere ): Memory usage will increase if you have significant amount of these objects, as you will store an extra Customer Object for each instance of Tools. This will gain you processor speed because you don't have to create and destroy Customer Objects for every method.

2.Option 2: (Keep a Customer object accessible only within method ): Memory usage will decrease and your application will become more processor intensive as you will create and destroy objects each time a method is accessed.

IMO if you instantiate a LOT of Tools objects then go for option 2 else if only a small amount if Tools Objects exist go for option 1

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Thanks a lot.. exactly what i was looking for wanted to know what were the side effects of creating many instances opposed to creating just one and using them every where.
0

Its depends on your requirement. For example if you don't want the class Tools outside of the method doCIdCheck, then 3rd options is preferred.

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so ummm.. it doesn't really matter? I already mentioned that ill need to use the Tools class pretty much everywhere in the Customer class.. so... was wondering on the effects of creating new instances where every needed or using a one instance created at the top level they have on memory management or the speed of the application.
0

You can override equals() method to check equality on cid in Customer. Example

And then instead of those loops you can use contains() of Collection method

So your doCIdCheck method will look like

public boolean doCIdCheck(Customer cId) {
    Tools tools = new Tools();// I don't know if you are initializing list
                                // in Tools constructor or not but it should
                                // be initialized in constructor or in declaration
    return tools.customers.contains(cId);
}
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3 Comments

ill try it and see thanks... and well to be honest i wanted to know in general whats the best way to use instances.. which has been answered by MaVRoSCy basically wanted to know whats the effects of creating multiple instances or creating one instance using them everywhere.
Hmmm... i don't think that'll work or maybe i'm doing something wrong.. basically a User Enters a Customer ID (int) and then it does a check on whether or not the Id exists... I TRIED your way but ummm.. i wouldn't know what argument am supposed to be passing to that (int)? coz it shows error and says expected: Customer found: int
new Customer(cId) create a constructor which will accept cId and assign it to variable. Then you can pass argument as Customer not int

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