bem’s blog

The following code does not compile:

public class A {
    public static void main(String[] args) {
        int i = Integer.parseInt(args[0]);
        switch (i) {
            case X: System.out.println("ONE!"); break;
            case Y: System.out.println("TWO!"); break;
            default: System.out.println("ZERO!"); break;
        }
    }
    public static final int X = B.getNumber("X");
    public static final int Y = B.getNumber("Y");
}

class B {
    public static int getNumber(String s) {
        if (s.equals("X")) {
            return 1;
        }
        else if (s.equals("Y")) {
            return 2;
        }
        else {
            return 0;
        }
    }
}

The compile error is:

A.java:5: constant expression required
            case X: System.out.println("ONE!"); break;
                 ^
A.java:6: constant expression required
            case Y: System.out.println("TWO!"); break;
                 ^
2 errors

I think I'll leave explaining why as an exercise for the reader. (Or for a future post. ;-)