Question

I would like to program in java two Boolean variables which are corelated in a way that one is allways false and one allways true. So if you set one to true the other one would automaticly change to false.

Answer 1

Don’t use variables – use methods.

Before using variables

class Before {
    boolean first;
    boolean second;

    boolean setFirst(boolean newValue) {
        first = newValue;
        second = !first;
    } 

    boolean setSecond(boolean newValue) {
        second = newValue;
        first = !second;
    }
}

make this better like so: use a single piece of data (which is what you really have) and use methods for the logic.

class After {
    private boolean value;

    boolean first() {
        return value;
    }

    boolean second() {
        return !value;
    }
}