Converting JOptionPane input to integer

Question

I'm trying to write a simple program that will ask for the user to enter a number in-between 1 and 10, then display the number. Now I have gotten part to work where if the number is outside of the range it asks again, but I can't seem to get it to ask again if anything aside from a number is inputted, such as % or hello.

The source code: (Cut out the top)

public static void main(String[] args){

    int number;                 //For holding the number
    String stringInput;         //For holding the string values until converted


    //------------------//
    //Introducing the user

    JOptionPane.showMessageDialog(null, "This is a program that will ask \n"
                                        + "you to enter a number in-between \n"
                                        + "1-10, if the number is not within \n"
                                        + "the parameters, the program will repeat.");


    //---------------------//
    //Get input from the user

    stringInput = JOptionPane.showInputDialog("Enter number.");

    number = Integer.parseInt(stringInput);


    //-----------------//
    //Checking the number

    while (number > 10 || number < 0){

        stringInput = JOptionPane.showInputDialog("That number is not within the \n"
                                                  + "allowed range! Enter another number.");

        number = Integer.parseInt(stringInput);

    }


    //-------------------//
    //Displaying the number

    JOptionPane.showMessageDialog(null, "The number you chose is "
                                        + number
                                        + ".");


    //-------------//
    //Closing it down
        System.exit(0);
}

The main problem is the:

number = Integer.parseInt(stringInput);

I can't seem to convert the data values properly. I already thought of something like using an if statement to determine if the number is an integer, but I couldn't figure out how to check. I wish I could do:

if (number == Integer)

As you can see I am still extremely new to Java, any help is appreciated, thanks for taking the time to read.

Answer 1

You need to surround the call to Integer.parseInt() with a try/catch block to detect invalid input, like:

try {
    number = Integer.parseInt(stringInput);
} catch (NumberFormatException e) {
    // Not a number, display error message...
}

Here is a solution:

String errorMessage = "";
do {
    // Show input dialog with current error message, if any
    String stringInput = JOptionPane.showInputDialog(errorMessage + "Enter number.");
    try {
        int number = Integer.parseInt(stringInput);
        if (number > 10 || number < 0) {
            errorMessage = "That number is not within the \n" + "allowed range!\n";
        } else {
            JOptionPane
                .showMessageDialog(null, "The number you chose is " + number + ".");
            errorMessage = ""; // no more error
        }
    } catch (NumberFormatException e) {
        // The typed text was not an integer
        errorMessage = "The text you typed is not a number.\n";
    }
} while (!errorMessage.isEmpty());

Answer 2

I'm trying to write a simple program that will ask for the user to enter a number in-between 1 and 10

• please to read Oracle tutorial How to use Dialogs - JOptionPane Features, then code should be very short and simple, without parsing an Integer from String

.

import java.awt.EventQueue;  
import javax.swing.Icon;  
import javax.swing.JOptionPane;  
import javax.swing.UIManager;  

public class MyOptionPane {  

    public MyOptionPane() {  
        Icon errorIcon = UIManager.getIcon("OptionPane.errorIcon");  
        Object[] possibilities = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};  
        Integer i = (Integer) JOptionPane.showOptionDialog(null,   
                null,  "ShowInputDialog",   
                JOptionPane.PLAIN_MESSAGE, 1,  errorIcon, possibilities, 0);

        // or

        Integer ii = (Integer) JOptionPane.showInputDialog(null,  
                "Select number:\n\from JComboBox", "ShowInputDialog",  
                JOptionPane.PLAIN_MESSAGE, errorIcon, possibilities, "Numbers");  
    }  

    public static void main(String[] args) {  
        EventQueue.invokeLater(new Runnable() {  
            @Override  
            public void run() {  
                MyOptionPane mOP = new MyOptionPane();  
            }  
        });  
    }  
}