Convert String to double in Java
You can use Double.parseDouble() to convert a String to a double:
String text = "12.34"; // example String
double value = Double.parseDouble(text);
For your case it looks like you want:
double total = Double.parseDouble(jlbTotal.getText());
double price = Double.parseDouble(jlbPrice.getText());
If you have problems in parsing string to decimal values, you need to replace "," in the number to "."
String number = "123,321";
double value = Double.parseDouble( number.replace(",",".") );