New and have a question on a probably simple question.

I am new to Java and I am working on a simple Algebra converter program to help out some of my friends in math class.
I know the code is probablly not done properly ( I'm still working out the kinks and am no where near done), but I am having a menu problem
when I import a class ive made for each individual part of the program the whole program closes when I exit just that one class.
Here's the code for each one.

Main.java

Code:

---

import java.util.Scanner;
public class Main
{
        static int Choice;
        static int Menu;
        public static void main(String[] args)
        {
                Menu = 0;
                while (Menu == 0)
                {
                        System.out.println("Welcome to the Algebra Converter V-1.0");
                        System.out.println();
                        System.out.println("choose one of the following conversion types below:");
                        Scanner x = new Scanner(System.in);
                        System.out.println("1) for Quadratic to Vertex form");
                        System.out.println("2) for Quadratic formula");
                        System.out.println("3) to exit");
                        Choice = x.nextInt();
                        System.out.println();
                        System.out.println();
                        if(Choice == 1)
                        {
                                QuadToVertex prog1 = new QuadToVertex();
                                prog1.main();
                        }
                        if(Choice == 2)
                        {
                                QuadForm prog2 = new QuadForm();
                                prog2.main();
                        }
                        if (Menu == 3);
                        System.exit(0);
                        System.out.println();
                        System.out.println("---------------------------------------------------");
                        System.out.println();
                        }
                }       
}

---

QuadForm.java

Code:

---

import java.util.Scanner;
public class QuadForm
{
        static double a;
        static double b;
        static double c;
        static double r;
        static double R;
        static String imag;
        public void main()
        {
                int program;
                program =0;
                while(program ==0)
                {
                imag = "";
                System.out.println("Please enter your a, b, and c values below:");
                Scanner input = new Scanner(System.in);
                System.out.print("a = ");
                a = input.nextDouble();
                System.out.println();
                System.out.print("b = ");
                b = input.nextDouble();
                System.out.println();
                System.out.print("c = ");
                c = input.nextDouble();
                System.out.println();
                if((b*b)-(4*a*c) >= 0)
                {
                        r = (-b - Math.sqrt((b*b)-(4*a*c)))/(2*a);
                        R = (-b + Math.sqrt((b*b)-(4*a*c)))/(2*a);
                }
                if((b*b)-(4*a*c)< 0)
                {
                        imag = "i";
                        r = Math.abs((-b - Math.sqrt((b*b)-(4*a*c)))/(2*a));
                        R = Math.abs((-b + Math.sqrt((b*b)-(4*a*c)))/(2*a));
                }
                System.out.println("x = "+imag+r+" or "+imag+R);
                }
        }
}

---

if I could get some help on this and maybe some help on how to better clean up my code I would greatly appreciate it.

Calling System.exit() is going to close your whole program. You probably want a branching statement instead: Branching Statements (The Java™ Tutorials > Learning the Java Language > Language Basics)

Hello. I'm not a java expert, so be sure to consult with an expert. But...

In class Main - shouldn't line 31 read if (choice == 3) { and then the system.exit will only operate if user chooses 3.

Ah, good catch. Yeah, ending your if statement with a semicolon basically short-circuits it and always performs the next line.

Quote:

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Originally Posted by Humphrey Bogart

Hello. I'm not a java expert, so be sure to consult with an expert. But...

In class Main - shouldn't line 31 read if (choice == 3) { and then the system.exit will only operate if user chooses 3.

---

yeah i was in the middle of just testing the menu and never changed menu back to choice lol


and thank you KevinWorkman ill check out the tutorial

i fixed the problem, I had used break before but i guess i wasnt using it right or something, but thank you for the help

btw how do i finish the tread? do i mark it as [SOLVED] or what? and how?

Quote:

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Originally Posted by legionunity

i fixed the problem, I had used break before but i guess i wasnt using it right or something, but thank you for the help

btw how do i finish the tread? do i mark it as [SOLVED] or what? and how?

---

You should be able to edit the post and mark it as solved.

Why do you have the code set up like:

Code:

---

        Menu = 0;
        while (Menu == 0)
        {

---

AND

Code:

---

                program =0;
                while(program ==0)
                {

---

This is what a 'do while' loop is for...

If you have to use 'breaks', your generally doing something wrong..

what would you use instead?

Quote:

---

Originally Posted by legionunity

what would you use instead?

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Like he said, he'd use a do-while. You should look into them, although I don't necessarily agree that a break means you're doing something wrong.

Quote:

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Originally Posted by KevinWorkman

\
although I don't necessarily agree that a break means you're doing something wrong.

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It is what our teacher tells us about once a week.. Mind giving me an example, excluding recursion, of where they would be needed? Where regular code would not suffice... Or a link.

Validating Lists of things.
If one of them is wrong, break.

The likes of indexOf on a Collection does the equivalent, in that it returns when it finds the object in question, essentially breaking the loop.

Quote:

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Originally Posted by penguinCoder

It is what our teacher tells us about once a week.. Mind giving me an example, excluding recursion, of where they would be needed? Where regular code would not suffice... Or a link.

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It might make sense in the context of your class, I'm not sure how your instructor is teaching things. But as a general rule, I don't think you can say that branching statements are inherently bad.

Another example is finding something in a List:

Code:

---

Object thingToLookFor = null;
for(Object thing : things){
    if(thing.isSomeCriteria()){
      //found it!
      thingToLookFor = thing;
      //we don't need to finish the loop
      break;
  }
}

---

There are a ton of other examples, such as doing some calculations in a loop (and once some stopping criteria is met, breaking out of that loop). So you can't say as a general rule that branching statements are bad. But maybe that makes more sense for how your instructor has organized your lessons, I don't know.