CTI Csc 211 Course homepage, Programming in Java I

Recap of Class 2

Two categories of data.

Primitive data such as integers, floating point numbers, characters etc ..
Objects such as Strings, Dialog Boxes, Frames, Customers, etc ..

The data type of an object is some class
When you install Java you get a bunch of classes you can use in your programs.
To get input into our programs we use the class JOptionPane
To use the class JOptionPane you have to know the package where it can be found then import it.
```
import javax.swing.JOptionPane;
```
Import statements must be placed before any class definitions in the file.
Class JOptionPane provides some methods used to pop up dialog boxes.
To get input into your program use the method showInputDialog from the JOptionPane class.
To prompt the user to enter their name, use the command

JOptionPane.showInputDialog("Enter your name");

The above command will produce a window similar to this

Method showInputDialog returns back into your program a string and always a string.
Can assign this string to a variable.

String name = JOptionPane.showInputDialog("Enter your name");

If a number is entered for computing, must convert the string that contains the digits into a number.
If the number is an integer, must parse it to an integer. If its a double must parse it to a double.

String inputPrincipal = JOptionPane.showInputDialog("Enter your name");
int    principal      = Integer.parseInt(inputPrincipal);

String inputRate = JOptionPane.showInputDialog("Enter the rate");
double rate      = Double.parseDouble(inputRate);

Integer and Double are class that come with java and are part of package java.lang
Classes part of package java.lang are automatically imported.
Use any text editor to enter your java codes. I will use textpad in the class.