Java static final values replaced in code when compiling?

Question

In java, say I have the following

==fileA.java==
class A
{  
    public static final int SIZE = 100;
}  

Then in another file I use this value

==fileB.java==  
import A;
class b
{
      Object[] temp = new Object[A.SIZE];
}

When this gets compiled does SIZE get replaced with the value 100, so that if I were to replace the FileA.jar but not FileB.jar, would the object array get the new value or would it have been hardcoded to 100 because that's the value when it was originally built?

Answer 1

Yes, the Java compiler does replace static constant values like SIZE in your example with their literal values.

So, if you would later change SIZE in class A but you don't recompile class b, you will still see the old value in class b. You can easily test this out:

file A.java

public class A {
    public static final int VALUE = 200;
}

file B.java

public class B {
    public static void main(String[] args) {
        System.out.println(A.VALUE);
    }
}

Compile A.java and B.java. Now run: java B

Change the value in A.java. Recompile A.java, but not B.java. Run again, and you'll see the old value being printed.

Answer 2

You can keep the constant from being compiled into B, by doing

class A
{  
    public static final int SIZE;

    static 
    {
        SIZE = 100;
    }
}