How to do a number keypad in java

I trying to figure out how to do a number keypad in java. I'm recently started using java, still have so much to learn. The following is what I came up with so far but it only returns one char at a time. Still researching this, but would really appreciate any assistance..thanks

currentButton = (JButton)event.getSource();
itemQuantity = currentButton.getText().charAt(0) - '0';

It looks like you're using the button's text as the value of one digit in a number representing itemQuantity. Each time a button is pressed, you should append that button's digit to a string:

String currentString = "";
currentString += currentButton.getText();

Then you can get the numeric value as @user1804740 suggests:

itemQuantity = Integer.parseInt(currentString);

Note, you'll have to handle any NumberFormatException thrown by the conversion.