AWT VS Swing components OR Heavyweight VS LightWeight Components

A heavyweight component is one that is associated with its own native (provided by OS) screen resource (commonly known as a peer). A lightweight component is one that "borrows" the screen resource of an ancestor  (which means it has no native resource of its own -- so it's "lighter"). Lightweight component is painted onto a heavyweight component.  There are some significant differences between lightweight and heavyweight components. And, since all AWT components are heavyweight and all Swing components are lightweight (except for the top-level ones: JWindow, JFrame,  JDialog, and JApplet), these differences become painfully apparent when  you start mixing Swing components with AWT components.

The differences boil down to the following:

• A lightweight component can have transparent pixels; a heavyweight is always opaque.

·         A lightweight component can appear to be non-rectangular because of its ability to set transparent areas; a heavyweight can only be rectangular.

• Mouse events on a lightweight component fall through to its parent; mouse events on a heavyweight component do not fall through to its parent.
• When a lightweight component overlaps a heavyweight component, the heavyweight component is always on top, regardless of the relative z-order of the two components.

You should not mix the heavyweight and lightweight components in an application. 

Advantages of Swing

1.         Swing components follow Model-View-Controller Architecture/Design Pattern.  Model stores the contents and allows them to modify.  View displays the contents in different forms.  Controller handles user input and interacts with view or model.  GUI components can follow this design pattern because they also have similar characteristics -

(i)                 contents (for example, text in text field, state of button etc)

(ii)               visual appearance (color, size etc)

(iii)             behavior(reaction  to events)

These 3 characteristics are similar to MVC pattern.  For example, a text box can have MVC pattern.  Its model part contains the text.  If a user hits a character key in a text box, the controller calls “insert” command of the model.  The model then tells the view to update itself.  The view never knows why the text changed. If a user hits a cursor key, then the controller, then controller may tell the view to scroll.  Scrolling the view had not effect on the underlying text so the model never knows that this event happened. 

2.         Wide variety of components

Along with standard components like buttons, check boxes, combo boxes, text fields, swing has rich set of components for creating trees, tables, tabbed panes etc. 

3.         Pluggable look and feel

            (Ref. To prev page)

4.         Nesting containers

AWT has certain restrictions as far as nesting containers.  But swing components provide flexibility.  You can have          a graphic in a list, combo box in toolbox, panels in list box etc. 

Disadvantages of Swing

1.                  Swing components are slower than AWT.

Swing components are not thread-safe.  You may not get correct output if you modify the model concurrently with the screen updater thread.