asked on

assign final value based on System.property

I've got a feeling what I'm trying to do is not possible, but I'll ask. I have a final float in an Interface. I want the value of it to be assigned according to a system property.

public interface MyConstants {
    public static final float MY_CONSTANTS = Float.parseFloat(
    		System.getProperty("myConstant").equalsIgnoreCase("2") ? "2.0" : "1.0");
}

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It must be this way, ie in an Interface and a final. So then set the property somewhere in the code:

System.setProperty("myConstant", "2"); // set to not 1

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MY_CONSTANTS always ends up being 0.0. I would have at least expected to always to 1.0. I've got a feeling that this isn't possible because of when the class/interface loading occurs. Basically I'm trying to kluge a #ifdef sort of thing.

CEHJ

That's fine. Example below. Bear in mind that the property must be set or you'll get an exception

public class Mc implements MyConstants {
    public Mc() {
        System.out.println(MY_CONSTANTS);
    }

    public static void main(String[] args) {
        new Mc();
    }
}

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SOLUTION

imladris

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krakatoa

So have you got "this far" then ? :

class MyCons implements MyConstants {

public static void main(String[] args){

System.out.println(MY_CONSTANTS);

}

}

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iface :

public interface MyConstants {
    public static final float MY_CONSTANTS = Float.parseFloat(
    		System.getProperty("java.version").equalsIgnoreCase("2") ? "2.0" : "1.0");
}

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krakatoa

Sry CEHJ - my clocks are running slow. ;)

zzynx

>> I want the value of it to be assigned according to a system property.
Why "according to"? Why not just simply assigning it the value of the property like this:

public interface MyConstants {
    public static final float MY_CONSTANTS = Float.parseFloat(System.getProperty("myConstant"));
}

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public class MC implements MyConstants {
    public MC() {
        System.out.println(MY_CONSTANTS);
    }

    public static void main(String[] args) {
        System.setProperty("myConstant", "2.0"); // You probably won't set this here of course. Just to prove it works.
        new MC();
    }
}

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allelopath

ASKER

imlandris:
Thanks for the explanation. So then, I'm not trying to emulate a #ifdef.

What I am trying to do is have MY_CONSTANTS have a default of 1 (if the property value is not specified) or get its valued from a system property if that system property is defined. My apologies to those who responded if I was not clear. In this case, the solution by zzynx is not what I need because a value must be specified for the system property.

ASKER CERTIFIED SOLUTION

CEHJ

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SOLUTION

zzynx

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CEHJ

zzynx

Thanx 4 axxepting