Static Variable

[Hendré Louw]

After defining a object as a static variable can I change one of the object's variables?

eg.

public static Person p = new Person();

later

p.setName("Hendre");

[Len Weincier]

Hi

Yes you can.

The more complete example is : 

class SomeClass {

public static Person p = new Person();

}

Then somewhere else you can say : 

SomeClass.p.setName("Hendre");

hth

Len

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[Etienne Pretorius]

Hello Hendre,

You should be able to change the values inside the class - provided the 'p' variable is within static scope. You are applying your access modifiers only on the reference and not to the class.

Kind Regards,

Etienne

On 09 Feb 2012, at 11:31 AM, Hendré Louw wrote:

[Ewald Horn]

Hi.

Yes, the static is not the same as in C++ - it simply means that the SAME variable will be shared across instances of the class.

It can still be modified, just like a normal instance variable.

Best regards,
Ewald

[Paul Gilowey (Santam)]

Hey Hendre,

 

Take care that you really need the variable to be static (see Ewald’s reply).

Thread safety can be an issue in a multi-threaded environment.

 

Regards

Paul.

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[Hendré Louw]

Thank you this answers my question.

[Moandji Ezana]

Also note that in this case:

class SomeClass {

public static Person p = new Person();

}

You can also do:

SomeClass.p = null;

You might consider making p final. However, globally shared mutable state is generally a bad idea. For concurrency reaons, as Paul mentioned, but also by creating hidden dependencies between classes, which can, for example, make testing harder.

Moandji

[Hendré Louw]

Can i also say

SomeClass.p = new Person();

--

[Len Weincier]

On 09 Feb 2012, at 2:07 PM, Hendré Louw wrote:

> Can i also say
>
> SomeClass.p = new Person();

Yes

Len

[Munaf Sheikh]

Can i also say

SomeClass.p = new Person();

yes. you can do anything you want to it. anything.

[Hendré Louw]

When I add final to the statement can I call p.setName("Hendre");

public static final Person p = new Person();

[Etienne Pretorius]

On 09 Feb 2012, at 2:33 PM, Hendré Louw wrote:

> When I add final to the statement can I call p.setName("Hendre");
>

Yes, because you are not making the instance final - you are making the reference variable final.

Kind Regards,
Etienne Pretorius

[Hendré Louw]

Fantastic! static and final works on the reference and not the instance. 

How do this relate to primitive types?

Can i do the following

public static int TEMP_VALUE = -1;

then later do the following

TEMP_VALUE = 2;

or in the case of final

public final static int TEMP_VALUE = -1;

then later do the following

TEMP_VALUE = 2;

[Munaf Sheikh]

static; yes,
Final: no  (compiler will complain)

[Etienne Pretorius]

On 09 Feb 2012, at 2:44 PM, Hendré Louw wrote:

Fantastic! static and final works on the reference and not the instance. 

How do this relate to primitive types?

Can i do the following

public static int TEMP_VALUE = -1;

Since these a non-objects, they will act the same as the reference in the previous examples.

Static = Class variable

Final = non-mutable;

Kind Regards,

Etienne Pretorius