Convert String Array to int using JOptionPane

showInputDialog always returns the input of the user as a String object, except from a variation where it returns the selected Object from the supplied ones. I am talking for Java version 8 for the sake of example.

Based on your question and comments, you basically want to:

1. Match String objects (their name) to integers (their value), so that you can calculate how much they will have to pay, plus the change afterwards.
2. Receive as input from the user the amount they will give, in order to calculate the change.

If so, then:

1. For the first case you can use some data structure(s) from which you will be able to match the locations with their value. For example a HashMap<String, Integer> can match the locations with their value, like so:

//Set up the origin options, along with their value:
HashMap<String, Integer> leavingOptions = new HashMap<>();
leavingOptions.put("North Avenue", 10);
leavingOptions.put("Quezon Avenue", 11);
leavingOptions.put("Kamuning", 12);
leavingOptions.put("Cubao", 13);
leavingOptions.put("Santolan", 14);
leavingOptions.put("Ortigas", 15);
leavingOptions.put("Shaw", 16);
leavingOptions.put("Boni", 17);
leavingOptions.put("Guadalupe", 18);
leavingOptions.put("Buendia", 19);
leavingOptions.put("Ayala", 20);
leavingOptions.put("Magallanes", 21);
leavingOptions.put("Taft", 22);

//Get user input for origin:
Object[] leavingOptionsArray = leavingOptions.keySet().toArray();
String leaving = (String) JOptionPane.showInputDialog(null, "Leaving from:", "Train Station", JOptionPane.QUESTION_MESSAGE, null, leavingOptionsArray, leavingOptionsArray[0]);

//Show output depending on user's input or cancel:
if (leaving != null)
    JOptionPane.showMessageDialog(null, "You shall pay: " + leavingOptions.get(leaving));
else
    JOptionPane.showMessageDialog(null, "Quiting...");

(note here that the casting of the returned value of the showInputDialog to a String reference is safe, just because the way we set up the options' array to contain only String objects)

Or you can use a String array with the locations along with an int array with the corresponding values, like so:

//Set up the origin options, along with their price:
String[] leavingOptions2 = new String[]{"North Avenue","Quezon Avenue", "Kamuning","Cubao","Santolan","Ortigas","Shaw","Boni","Guadalupe","Buendia","Ayala","Magallanes","Taft"};
int[] price = new int[]{10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22};

//Get user input for origin:
Object leaving2 = JOptionPane.showInputDialog(null, "Leaving from:", "Train Station", JOptionPane.QUESTION_MESSAGE, null, leavingOptions2, leavingOptions2[0]);

//Show output depending on user's input or cancel:
if (leaving2 != null) {

    //Find the price of the selected location:
    int p = -1;
    for (int i = 0; i < price.length; ++i)
        if (leaving2.equals(leavingOptions2[i])) {
            p = price[i];
            break;
        }

    JOptionPane.showMessageDialog(null, "You shall pay: " + p);
}
else
    JOptionPane.showMessageDialog(null, "Quiting...");

Or even better, you can use another object type other than String for the options array, for example a class named Location which will have the name and the price as properties, the toString method of which will return the name.

2. For the second part, obtain the user's input as a String from a JOptionPane and use Integer.parseInt(...) method on the user's input so as to be able to calculate the change afterwards, like so:

String paymentString = JOptionPane.showInputDialog(null, "Enter payment amount:", "Payment", JOptionPane.QUESTION_MESSAGE);

if (paymentString != null) {
    try {
        int payment = Integer.parseInt(paymentString);
        JOptionPane.showMessageDialog(null, "You chose to pay: " + payment);
        //Calculate change here...
    }
    catch (final NumberFormatException exception) {
        JOptionPane.showMessageDialog(null, "The input was invalid (not an 'int').");
    }
}
else
    JOptionPane.showMessageDialog(null, "Quiting...");

Remember that parseInt will throw a NumberFormatException (which is a RuntimeException) if its input String is not an int, so you will have to check for that using a try-catch block.