Initialize a static final field in the constructor

Question

public class A 
{    
    private static final int x;

    public A() 
    {
        x = 5;
    }
}

• final means the variable can only be assigned once (in the constructor).
• static means it's a class instance.

I can't see why this is prohibited. Where do those keywords interfere with each other?

Answer 1

Think about it. You could do this with your code:

A a = new A();
A b = new A(); // Wrong... x is already initialised

The correct ways to initialise x are:

public class A 
{    
    private static final int x = 5;
}

or

public class A 
{    
    private static final int x;

    static
    {
        x = 5;
    }
}