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Editorial Team
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Asked: 2026-05-26T14:30:51+00:00

I followed the advice given here in several posts on how to declare global

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I followed the advice given here in several posts on how to declare global contants:

public class Constants {

    public static final int i1 = 1;
    public static final int i2 = 2; 
    }

I just include this class in my project and refer to the constants like this:

in any other class...
    GlobalsVars.gi1 = Constants.i1;

(ps I hope this is OK and do not need to do anything to the Constants class like initializing or anything.)

But as I found out here: assigning int to Integer using static global variables is not a good idea. My app crashes sometimes when accessing the constants.

Though I find it really weird, since my app is rather small, but may be the Constants class – not an activity – is really removed from the memory in certain cases, though I access its constants in all my activities. That’s why I would think it should not be removed from memory anyway.

But for sure, my app crashes in certain cases when accessing the Constants.i1 value.

What would be the best way just to declare some constants in a reliable way. (In c-Derivatives there are the easy to use macros) But there is nothing like this in Android.

-> all I need are “reliable” constants in Java…

EDIT:

declaration of GlobalVars class added

public class GlobalVars {
    public static Integer gi1;
    public static Integer gi2;
}

Many thanks

EDIT:
added crash log

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xxxx.xxxx/com.xxxx.xxxx.screens.One_screen}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1830)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1851)
at android.app.ActivityThread.access$1500(ActivityThread.java:132)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1038)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:150)
at android.app.ActivityThread.main(ActivityThread.java:4293)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.xxxx.xxxx.screens.Settings_screen.presentOnScreen(One_screen.java:172)
at com.xxxx.xxxx.screens.Settings_screen.onCreate(One_screen.java:49)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1794)
… 11 more

and the line 172 in One_screen is:

if (GlobalVars.gi1 == Constants.i1){
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1 Answer

  1. Editorial Team

    Your NullPointerException is occurring because GlobalVars.gi1 is null, not Constants.i1. You should always be able to rely on hard-coded integer values as they are part of the class definition.

    If you simply wish to store a small number of long-lived integer variables. I suggest looking into SharedPreferences to store them (instead of GlobalVars).

    You can find out more here.

    If you wish to pass data only from one Activity to another, look at adding values to the Intent‘s extras using Intent.putExtra and retrieve the extras Bundle in the next Activity using Intent.getExtras on the Intent retrieved from Activity.getIntent.

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