Fisiks

package fisiks;
import java.util.ArrayList;
import java.util.Scanner;
//------------------------------------------------
//FISIKS HOMEWORK HELPER WRITTEN BY JOSEPH AQUIARE
// RELEASED UNDER THE GNU GENERAL PUBLIC LICENSE
//        FEEL FREE TO EDIT, FORK, ETC.
//     http://www.gnu.org/licenses/gpl.html
//------------------------------------------------
public class Fisiks {
    static int RUNTIMECOUNT = 0;
    static introduction i        = new introduction();
    static velocity v            = new velocity();
    static acceleration a        = new acceleration();
    static ArrayList<equation> e = new ArrayList<equation>();
    static Scanner sc            = new Scanner(System.in);
    public static void main(String[] args){
        e.add(v);
        e.add(a);
        i.intro();
        prompt();
    }
    static void prompt(){
        if(RUNTIMECOUNT > 0){
            System.out.println("AVAILABLE EQUATIONS:");
            for(int i = 0; i < e.size(); i++)
                System.out.println((i+1) + ") " + Fisiks.e.get(i));
        }
        RUNTIMECOUNT++;
        System.out.println("\nWhat equation would you like to use? (Ex. \"1\")");
        e.get(sc.nextInt() - 1).askInfo();
    }
    public ArrayList<equation> getList(){
        return e;
    }
}

class introduction extends Fisiks{ //intro seqence
    void intro(){
        System.out.println("FISIKS HOMEWORK HELPER - V1.0.0\n\n" +
                           "AVAILABLE EQUATIONS:");
        for(int i = 0; i < super.getList().size(); i++)
            System.out.println((i+1) + ") " + Fisiks.e.get(i));
    }
}
//DEFAULT EQUATION PARENT CLASS
class equation{
    private String eq = "DEFAULT EQUATION";
    public String toString(){
        return eq;
    }
    public void askInfo() {
    }
}
// VELOCITY EQUATION CHILD CLASS
class velocity extends equation{
    private String eq = "VELOCITY: v = d/t";
    private double d,v,t;
    private Scanner sc = new Scanner(System.in);
    double DandT(double distance, double time){
        System.out.print("v = ");
        return distance/time;
    }
    double DandV(double distance, double velocity){
        return distance/velocity;
    }
    double VandT(double velocity, double time){
        return velocity*time;
    }
    public void askInfo(){
        System.out.println("You've asked for: " + toString() + "\n" +
                           "What are you solving for? (Ex. \"t\")");
        String s = sc.nextLine();
        switch(s){
            //velocity solving sequence
            case("v"):  System.out.println("Please enter d, and then t:");
                        System.out.print("D:");
                        d = sc.nextDouble();
                        System.out.print("T:");
                        t = sc.nextDouble();
                        System.out.println(DandT(d,t) + " m/s");
                        break;
            //distance solving sequence
            case("d"):  System.out.println("Please enter v, and then t:");
                        System.out.print("V:");
                        v = sc.nextDouble();
                        System.out.print("T:");
                        t = sc.nextDouble();
                        System.out.println(VandT(v,t) + " m");
                        break;
            //time solving sequence
            case("t"):  System.out.println("Please enter d, and then v:");
                        System.out.print("D:");
                        d = sc.nextDouble();
                        System.out.print("V:");
                        v = sc.nextDouble();
                        System.out.println(VandT(d,v) + " s");
                        break;
        }
        System.out.println("Would you like to use another equation? (Ex. \"y\"/\"n\")");
        String answer = sc.nextLine();
        switch(answer){
            case("y"): Fisiks.prompt(); break;
            default: System.exit(0);
        }
    }
    public String toString(){
        return eq;
    }
}
//ACCELERATION EQUATION CHILD CLASS
class acceleration extends equation{
    private String eq = "ACCELERATION: a = v/t";
    private double a,v,t;
    private Scanner sc = new Scanner(System.in);
    double VandT(double velocity, double time){
        return velocity/time;
    }
    double VandA(double velocity, double acceleration){
        return velocity/acceleration;
    }
    double AandT(double acceleration, double time){
        return acceleration*time;
    }
    public void askInfo(){
        System.out.println("You've asked for: " + toString() + "\n" +
                           "What are you solving for? (Ex. \"a\")");
        String s = sc.nextLine();
        switch(s){
            //acceleration solving sequence
            case("a"):  System.out.println("Please enter v, and then t:");
                        System.out.print("V:");
                        v = sc.nextDouble();
                        System.out.print("T:");
                        t = sc.nextDouble();
                        System.out.println(VandT(v,t) + " m/s^2");
                        break;
            //velocity solving sequence
            case("v"):  System.out.println("Please enter a, and then t:");
                        System.out.print("A:");
                        a = sc.nextDouble();
                        System.out.print("T:");
                        t = sc.nextDouble();
                        System.out.println(AandT(a,t) + " m/s");
                        break;
            //time solving sequence
            case("t"):  System.out.println("Please enter v, and then a:");
                        System.out.print("V:");
                        v = sc.nextDouble();
                        System.out.print("A:");
                        a = sc.nextDouble();
                        System.out.println(VandA(v,a) + " s");
                        break;
        }
        System.out.println("Would you like to use another equation? (Ex. \"y\"/\"n\")");
        String answer = sc.nextLine();
        switch(answer){
            case("y"): Fisiks.prompt(); break;
            default: System.exit(0);
        }
    }
    public String toString(){
        return eq;
    }
}