Behavioral Patterns : Mediator

Properties:

-          Provides communication between set of classes without communicating classes needing to know each other. Thus mediator pattern helps to reduce coupling.

-          If number of communicating classes is high, mediator class may get too complicated.

Implementation:

-          A mediator interface declares actions of the mediator.

-          Concrete Meadiator implementations of mediator defines those actions.

-          Concrete Colleagues are classes that communicates.

Java Standard Library Implementations:

-          javax.swing.ButtonGroup

Example Usage:

//Create the radio buttons.

JRadioButton firstButton = new JRadioButton("FirstButton"); // colleague 1

JRadioButton secondButton = new JRadioButton("SecondButton"); // colleague 2

JRadioButton thirdButton = new JRadioButton(dogString); // colleague 3

firstButton.setSelected(true);

// Once a button is selected, other buttons must be de-selected.

// So buttons must communicate.

ButtonGroup group = new ButtonGroup();// Mediator class

group.add(firstButton);

group.add(secondButton);

group.add(thirdButton);