Java最终变量初始化

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;
    }
}

Answer 1

从大小中删除static修饰符...我很确定你不想要它;）

Answer 2

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.

Answer 3

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

public class Ore {

    protected static final float size;

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

Answer 4

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*/;