Method in class

class Demo{
    double height;
    double base;
    void vol(){
        System.out.println(0.5*base*height);
    }
}
public class Main{
    public static void main(String args[]){
        Demo dm = new Demo();
        dm.base = 5.5;
        dm.height = 6.5;
        dm.vol();
    }
}