How To Declare Constants in Android without using public static final

Question

I am developing a Bluetooth app that is always running until user uninstalls app or switches off their mobile. I am getting an error message: "unfortunately app stopped working". From my initial research this appears to be a memory leak issue. So far I have found out that any object with static reference will leak memory. So I need to remove static references of variables. My project has many constants, how can I write constants without using public static final?

currently, i am using something like this:
public static final int NOTIFICATION_ID=1234;

Update

I think My question needs some more info so here it is

private static variable problem 1) Hi Friends,My app uses database has 9 tables each table has 7 to 13 columns,So the column name I am declaring like private static final String COLUMN_NAME_ACTIVE = "active"; similarly more than 70 static variables has been declared. 2)some of the instances to access in another class i have declared 3)1 util class it is a static class

static final constants are not your problem here. They take up some memory, but it's all allocated at startup and never move afterward. You might have a more complex problem. https://stackoverflow.com/questions/6470651/creating-a-memory-leak-with-java — litelite, Jul 14 '17 at 13:21
"currently i am using like public static final int NOTIFICATION_ID=1234;" -- that is not a memory leak. "When I searched I came to know this is memory leak issue" -- you do not crash from a memory leak, unless you are getting an `OutOfMemoryError`. — CommonsWare, Jul 14 '17 at 13:31

score 1 · Answer 1 · edited Jul 14 '17 at 15:21

1

You can define constants in res/values under xml format and refer to it using R. In this case R.integer..

Example:

<resources>
    <integer name="notif_id">1234</integer>
</resources>

Example usage:

someMethodName(R.integer.notif_id)

edited Jul 14 '17 at 15:21

petey

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answered Jul 14 '17 at 13:40

Tomatocurry1

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`R.id` is just a generated interface full of static final variables. – litelite Jul 14 '17 at 14:06
My bad. I didn't realize. I guess this thread might as well be "different ways of making static final variables without using the words 'static' and 'final'" with the number of actually static final answers that are here. – Tomatocurry1 Jul 14 '17 at 14:11
That's what it is right now indeed. Because, anyway, static final is the only viable way to store these constants. – litelite Jul 14 '17 at 14:12

AbhayBohra · Answer 2 · 2017-07-14T13:26:03.467

0

Create an Interface class and define variables there

public interface Constants{

String Name="AAA";
String Age="20";

}

And use it like this

String name=Constants.Name;

edited Jul 14 '17 at 13:26

answered Jul 14 '17 at 13:20

AbhayBohra

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He can directly use interface variable no need of String name=Constants.Name; – akhilesh0707 Jul 14 '17 at 13:24
Yes but i was just trying to explain – AbhayBohra Jul 14 '17 at 13:25
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Variables in an interface are static final (https://stackoverflow.com/questions/2430756/why-are-interface-variables-static-and-final-by-default) – litelite Jul 14 '17 at 13:30
I dint know this thanks for info ,but i need 1 clarification is this creates memory issue? – Sachin Gururaj Acharya Jul 17 '17 at 05:55

score 0 · Answer 3 · answered Jul 14 '17 at 13:24

0

you need to persist data, you can use SharedPreferences like this :

Decalre your SharedPreferences:

SharedPreferences sharedpreferences = getSharedPreferences("mypref", Context.MODE_PRIVATE);

write to your SharedPreferences :

Editor editor = sharedpreferences.edit();
editor.putString("key", "value");
editor.commit();

and read from it when you want :

String value = sharedpreferences.getString("key","defaultValue");

answered Jul 14 '17 at 13:24

Oussema Aroua

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But then he will have to initialize it, which means he will need a bunch of constants/litteral somewhere anyway. And it will make accessing the constants difficult because it will require a context and more than a single line. – litelite Jul 14 '17 at 13:33
he needs only to save the value of the `NOTIFICATION_ID` – Oussema Aroua Jul 14 '17 at 13:34
He gave one exemple, does not mean he have a single constant in his whole app – litelite Jul 14 '17 at 13:35
maybe but he doesn't specify what he needs exactly – Oussema Aroua Jul 14 '17 at 13:37
Even if he only need one value, he would still need another constant to store the key anyway. – litelite Jul 14 '17 at 14:04
Values in `SharedPreferences` are indexed by a key. So he needs to have the key to access the value he stored. – litelite Jul 14 '17 at 14:11
take the notification_id example save the value and get it when you need it by the key of notification_id – Oussema Aroua Jul 14 '17 at 14:12
so your key is "notification_id" which IS a constant by itself if you need to pass it to the SharedPreferences – litelite Jul 14 '17 at 14:13
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/149233/discussion-between-oussema-aroua-and-litelite). – Oussema Aroua Jul 14 '17 at 14:14

Rahul · Answer 4 · 2017-07-14T13:40:43.130

0

Usually I declare constants in a single file, that will help me and other developers to update any configuration/value.

You can achieve same by using interface. Interfaces are static final by default and variable declarations that are declared to be both static and final.

public interface MyConstants {
  String SERVER_URL = "my_server_address";
  int SPLASH_LAUNCH_TIME = 1000;
}

You can use constants in Interfaces by 2 ways -

a. Either call them directly, like MyConstants.SERVER_URL;

b. Implement that interface in your class and access all constants directly.

Choose your approach wisely, by using approach 2 you will flood all constants in your class. Even they are not required in that class.

edited Jul 14 '17 at 13:40

answered Jul 14 '17 at 13:33

Rahul

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You should mention that "variables" in interfaces are `static final` *implicitly*, even if not being declares so, which is what the OP wanted to avoid... – Timothy Truckle Jul 14 '17 at 13:37
@TimothyTruckle thank you for pointing that, updated my answer – Rahul Jul 14 '17 at 13:41

score 0 · Answer 5 · answered Jul 14 '17 at 15:02

0

You can use an Enum:

public enum Gender {
   MALE,
   FEMALE
}

And access it like this:

Gender.MALE

answered Jul 14 '17 at 15:02

Hugo sama

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It seems that in java an enum just generate a class with a bunch of static final inside. https://stackoverflow.com/questions/143285/how-much-memory-do-enums-take – litelite Jul 14 '17 at 15:05

How To Declare Constants in Android without using public static final

5 Answers5