Java Final Variable Initialization

Question

I get an error that says that the size variable might not have been initialized even though i have initialized it in the constructor. why doesn't this work ?=

public class Ore {

protected static final float size;
protected String name;
protected int itemID;
protected ArrayList<Mineral> minerals;

public Ore(float size, String name, int itemID){
       this.size = size;
       this.name = name;
       this.itemID = itemID;
    }

    public String getPrizeData(int itemNumber){
       String data = null;

       return data;
    }

    public float getPrice(){
        float price = 0;

        return price;
    }
}

vikingsteve · Accepted Answer · 2014-06-17 12:15:33Z

4

drop the static modifier from size... I'm pretty sure you don't want it there ;)

answered Jun 17, 2014 at 12:15

vikingsteve

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Akash Thakare · Accepted Answer · 2014-06-17 12:20:08Z

1

protected static final float size;

Combination of final and static is considered CONSTANT in java and the Compiler replaces the constant name (Here size) everywhere in the code with its value during compilation so it's not allowed here to initialize it in constructor and generates compile time error.

So either go for the vikingsteve's solution or initialize it at the time of declaration.

answered Jun 17, 2014 at 12:20

Akash Thakare

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2 Comments

RossC Over a year ago

I tried to write something like this and got horribly muddled. Thanks for a clear concise explanation, it's obvious to me now!

fabian Over a year ago

"the compiler replaces the constant name everywhere in the code [...] during compilation" is simply not true. If you initialize it e.g. with the value from a static function the right hand side of the assignment is no longer a constant expression and can't be inlined by the compiler (JIT compilation may be a different story).

fabian · Accepted Answer · 2014-06-17 12:17:14Z

0

size is a static field. As such it has to be initialized directly in the declaration or form a static initializer, i.e. like this:

public class Ore {

    protected static final float size;

    static{
        size = // add something here
    }
    //....
}

answered Jun 17, 2014 at 12:17

fabian

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1 Comment

vikingsteve Over a year ago

Worth noting that static contexts are messy, hard to test and debug, and should be avoided if at all possible.

Bathsheba · Accepted Answer · 2014-06-17 12:24:49Z

0

The way you have things it would be possible to derive a class from Ore and implement a public static function in that derived class that refers to size. This is one way in which size could be accessed prior to initialisation and the compiler is correctly identifying that.

One fix would be to use a static initialiser block in Ore which initialises size, or set its value to a literal: protected static final float size = /*ToDo - a literal here*/;

answered Jun 17, 2014 at 12:24

Bathsheba

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