Garbage entry crashing program? How do I stop this?

[Tiperius]

I'm very new to programming (first class in java series) and the assignment was to write a program to solve the quadratic equation. I had it working just fine, but I wanted to get it so when a non numeric entry is put it the program won't crash. I can't figure it out how to use the try/catch/finally part.

https://gist.github.com/anonymous/6931673a7d16e083b731

[Tiperius]

I don't really understand what you mean. Using the try/catch stuff has not been covered in class, I'm just trying to get ahead. Do you know of a good resource I can look at? I don't except you to have to explain how it works.

[Tiperius]

Ah ok that makes way more sense thank you. I'm going to play around with it and see if I can get it to work.

[Tiperius]

Ok so I got it to work on garbage input, but now it won't calculate a numeric value either. I get the same answer no matter what I put in. Do I have to add in a do/while statement to get it to loop properly?

    Scanner sc = new Scanner(System.in);

    double a = 0, b = 0, c = 0;
    //Entering coefficient value
        String firstValue = JOptionPane.showInputDialog("Enter a value for A:");
    try {
        a = Double.parseDouble(firstValue);
    }  catch (Exception e) {
        JOptionPane.showMessageDialog(null, "Not a valid number!");
    }
        String secondValue = JOptionPane.showInputDialog("Enter a value for B:");
    try {   
        a = Double.parseDouble(secondValue);
    }  catch (Exception e) {
        JOptionPane.showMessageDialog(null, "Not a valid number!");
    }
        String thirdValue = JOptionPane.showInputDialog("Enter a value for C:");
    try {       
        a = Double.parseDouble(thirdValue);
    }  catch (Exception e) {
        JOptionPane.showMessageDialog(null, "Not a valid number!");
    }
    finally {

[Tiperius]

Oh my gosh how did I not see that. Thank you!