Boxes and Tubes Application - Coursework Example

1. User interface.
   • The main form

The main form is the form that is displayed when the application is launched. It has three buttons namely MENU ITEM, ORDER MENU & EXIT.

On clicking MENU ITEM, the available items are displayed on a different form. This only offers a description of these items and how to place an order. From this form, you can either go back to the main menu or exit the system.

The ORDER MENU button launches the Ordering System Form. This is the main form in which the user states their requirements and the system compiles the items ordered and computes the price.

1. CODE EXPLANATION.

CLASS PROJECT.JAVA

This is the main class of the project. The package keyword appears at the beginning of every class declaration. This is used to make the class reusable in other classes thus enhancing importing one class to another.

The import declaration helps the compiler to locate classes used in the program. These are actually predefined packages that save the programmer the pain of having to ‘re-invent the wheel’.

public class Project extends JFrame implements ActionListener declares a class which is we are going to construct our GUI. The extended keyword indicates that the class is a child of class JFrame and represents an inheritance relationship. Implements keyword is essential while using an interface for it indicates that all the methods used in the interface must be declared with the signature declared in the interface declaration in this case ActionListener. The ActionListener implements event handling.

We, therefore, go ahead and declare all the components of the form. Note that the programmer must be able to pre-visualize the desired form before putting down the code for creating it. Also, it is worth noting that for the neatness all the controls are placed within panels named Jpanel.

Public static void main (String [] args) is the start point of every Java application of which every application must have one and only one method named main without which the application will not execute. The void keyword indicates that the application will not return any information.

public Project() is the function that actually creates the GUI.

public void actionPerformed(ActionEvent e){ is put into action when the user does any of the actions declared within this function.

Finally, we declare the function for carrying out the calculation.

public double calculates (double grade). The variables and constants here can be changed to bring about the desired outcome such as factoring in tax, discounts, and the like.

CLASS BOXESTUBES.JAVA

This class is much similar to the project.java class above. It is used to create the start-up form. The procedure is the same in all aspects except for the minor specialties of the form.

CLASS ORDERMENU.JAVA

This class carries the code for creating the order menu form called frames in java. As in all the other classes, we start by packaging our class followed by importing the desired in-built classes.

class order menu extends JFrame implements ActionListener declares a class that inherits from JFrame and implements ActionListener which detects user action such as clicking typing, pressing enter or any such action that the programmer my desire to capture. As in the other two classes, we declare the controls we intend to place in the form such as JButton, JRadioButton, JTextField, JCheckBox, JComboBox, and the JTextArea followed by variable declaration.

public static void main(String[] args){ method constructs  the required frame (form). The frame. pack()function causes the window to be resized to fit the preferred size by automatically adjusting its height and width.

The other parameters of the window are self-explanatory.

public order menu(){ function is the window constructor.

It is in this function that we now place all the controls that we had declared earlier in the desired position. As previously stated we place the controls within panels for better organization. Also, note that since a panel is a container we can have a panel within another panel. While adding controls into a panel, we use the add() function. Ideally, every control should be labeled for the purpose of clarity.

The North, south, west,  east keywords are used to set the position of the panel within the window.

The try{ } block encloses code that might throw an exception and the code within that block should not execute should the exception occur. Should the exception occur, the catch block handles the exception. This is important especially when we expect the user to make a mistake when entering the details of the container

The code in most cases is self-explanatory and where there seem to be complications, I have tried my best to make it clear and easy to understand. Also note that in this explanation I have not included the following classes; circular.java, open.java, rectangular.java, circular.java. This is because I had created the classes in the initial stage of application design which later changed and never implemented at all. You can actually comment on all these classes and the application will run just fine.

 Please feel free to ask for further clarification should the need arise.