class Account {
    int gamma (int val1, ...) {
	    //some computations
		             return c-2*a;
    }
}

class Account {
    int gamma (int val1, ...) {
        Calculations calculations = new Calculations(val1, ...).invoke();
        int c = calculations.getC();
        int a = calculations.getA();
        return c-2*a;
    }
    private class Calculations {
        private int val1;
        ...
        private int a;
        private int c;
        public Calculations(int val1, ...) {
            this.val1 = val1;
            ...
        }
        public int getA() {return a;}
        public int getC() {return c;}
        public Calculations invoke() {
            ...//computations
               return this;
        }
    }
}