Ohm's Law Calculator - Main Class

//Main Class
import javax.swing.JOptionPane;

public class Main extends response
{
    public static void main(String[] args)
    {
        response obj = new response();
        Mathoutput outputobj = new Mathoutput();

        String input = "";
        int solvefor = 0;
        input = JOptionPane.showInputDialog(null, "What unit are you solving for?\nPower,"
                + " Voltage, Current, Or Resistance?\nType the in variable you are solving for to select.   ");


        if(!(input != null && !input.isEmpty()))
            {
            JOptionPane.showMessageDialog(null,"No Imput found!","Input Error",JOptionPane.WARNING_MESSAGE);
            }
        else
            {
            if(input.equalsIgnoreCase("Power"))
                {
                solvefor = 1;
                }
            if(input.equalsIgnoreCase("Voltage"))
                {
                solvefor = 2;
                }
            if(input.equalsIgnoreCase("Current"))
                {
                solvefor = 3;
                }
            if(input.equalsIgnoreCase("Resistance"))
                {
                solvefor = 4;
                }

            }

        //Generate variable selector
        switch(solvefor)
        {
        case 1:
        input = JOptionPane.showInputDialog(null,"[Solving for Power]\nFrom the entries below, "
                + "choose the option that contains \nthe variables that you currently have. To Select: "
                + "Type \nthe numeric value of the option to enter a selection. "
                + "\n\nOption #1: Voltage & Resistance"
                + "\nOption #2: Resistance & Current"
                + "\nOption #3: Voltage & Current");
        break;
        case 2:
        input = JOptionPane.showInputDialog(null,"[Solving for Voltage]\nFrom the entries below, "
                + "choose the option that contains \nthe variables that you currently have. To Select: "
                + "Type \nthe numeric value of the option to enter a selection. "
                + "\n\nOption #1: Resistance & Current"
                + "\nOption #2: Power & Current"
                + "\nOption #3: Power & Resistance");
        break;
        case 3:
        input = JOptionPane.showInputDialog(null,"[Solving for Current]\nFrom the entries below, "
                + "choose the option that contains \nthe variables that you currently have. To Select: "
                + "Type \nthe numeric value of the option to enter a selection. "
                + "\n\nOption #1: Power & Resistance"
                + "\nOption #2: Power & Voltage"
                + "\nOption #3: Voltage & Resistance");
        break;
        case 4:
        input = JOptionPane.showInputDialog(null,"[Solving for Resistance]\nFrom the entries below, "
                + "choose the option that contains \nthe variables that you currently have. To Select: "
                + "Type \nthe numeric value of the option to enter a selection. "
                + "\n\nOption #1: Power & Current"
                + "\nOption #2: Voltage & Power"
                + "\nOption #3: Voltage & Current");
        break;
        }

        double optionselection = Double.parseDouble(input);

        obj.does(solvefor,optionselection,input);

        outputobj.createfinaloutput(obj.power,obj.voltage,obj.current,obj.resistance,solvefor,optionselection);

    }
}