JAP Hybrid 1

Internationalization

• Internationalization allows adapting an application to different languages and regions without code changes
• Internationalization is sometimes shortened to "i18n" because there are 18 letters between the first "i" and the last "n"

Benefits of Internationalization

• A single executable can run worldwide with localized data
• Text elements and GUI labels are not hardcoded
• New languages can be supported without recompilation
• Culturally dependent data (dates, currencies) is formatted according to the user's region/language

Hello World Example

• Code loads a resource bundle file named "MessagesBundle" to retrieve messages for the default locale
• The resource bundle file is a properties file with key-value pairs for each language
• To support multiple languages, create separate resource bundle files for each language
• To switch languages, change the locale and reload the resource bundle

Locale Details

• Locale can be defined using: Locale currentLocale = new Locale(language, country);
• Specific bundle can be defined: ResourceBundle messages = ResourceBundle.getBundle("MessagesBundle", currentLocale);
• The resource bundle is important to dynamically reference properties in code
• Locale has properties like locale.Country, locale.Language, and locale.Name
• Locale can be adjusted using parameters: Locale locale = new Locale(language, country);
• Example locale definition: Locale locale = new Locale("en", "CA");

Locale Adjustments

• With the locale, numbers, dates, times, and currency formats can be adjusted
• Example: NumberFormat numberFormat = NumberFormat.getNumberInstance(locale);
• Example: DateFormat formatter = DateFormat.getDateInstance(DateFormat.DEFAULT, locale);
• Example: DateFormat formatter = DateFormat.getTimeInstance(DateFormat.DEFAULT, locale);
• Example: NumberFormat formatter = NumberFormat.getCurrencyInstance(locale);

Nested Classes

• Java allows defining a class within another class
• A nested class is defined inside another class
• The containing class is sometimes called the "outer" or "enclosing" class
• A top-level class is not part of another class
• Nested classes are divided into static and non-static categories

Inner Classes

• Inner classes were introduced in Java 1.1
• Inner classes can make multimedia applications more elegant and maintainable
• Inner classes are an integral part of many Java library classes
• Inner classes are used extensively in Java GUI application event handling
• Anonymous inner classes are useful for implementing an interface that defines only one method
• These interfaces are called Single Abstract Method (SAM) interfaces
• Lambda expressions are an alternative to SAM interfaces since Java 8
• Inner classes are useful for creating adapter classes, if the interface defines more than one abstract method
• Adapter classes implement methods of a class or interface into a different method, that the class or interface does not implement
• Adapter classes implemented as inner classes have access to the enclosing class's fields and methods
• Inner classes that implement one-method interfaces can be passed as arguments
• Inner Class code sample:

WindowListener wl = new WindowAdapter() {
    public void windowClosing(WindowEvent e) {
        System.exit(0);
    }
};
addWindowListener(wl);

• The WindowListener instance handles GUI application window close button events
• java.awt.event.WindowAdapter is an abstract class implementing all methods of the java.awt.event.WindowListener interface with no operations
• WindowAdapter cannot be directly instantiated because it is abstract
• You must write a class extending WindowAdapter and override the appropriate method
• This class can be a top-level class or an inner class
• In the code sample, an anonymous inner class creates a WindowListener
• The anonymous class extends WindowAdapter and overrides the windowClosing() method
• In the addWindowListener() method call, the anonymous inner class definition and instantiation are used as a parameter
• Similar approaches create ActionListener objects for handling button actions
• Anonymous inner classes can be replaced with lambda expressions if the interface is a SAM interface

UML Review

• UML (Unified Modeling Language) is a general-purpose, graphical modeling language for software engineering
• UML helps specify, visualize, construct, and document software system elements
• UML was initially developed by Grady Booch, Ivar Jacobson, and James Rumbaugh in 1994-95
• It was standardized by the Object Management Group in 1997

UML Details

• UML is a standardized visual modeling language for software engineering
• It specifies, visualizes, constructs, and documents software system artifacts
• It aids in designing and characterizing object-oriented software systems
• It describes the workings of both hardware and software systems

Conceptual Modeling

• A conceptual model consists of interrelated concepts for understanding objects and their interactions
• It's the first step in drawing UML diagrams

Object-Oriented Concepts

• Object: A real-world entity and a fundamental building block of UML
• Class: A software blueprint for objects, defining variables and methods
• Abstraction: Portrays essential object characteristics while hiding irrelevant details
• Inheritance: Deriving a new class from existing classes
• Polymorphism: Representing objects with multiple forms for different purposes
• Encapsulation: Binds data and objects as a single unit
• OO analysis identifies objects for designing a system
• OO design combines identified objects
• OO analysis identifies system objects and their relationships
• The purpose of OO is to make a design that is executable when the concepts of OO are employed

OO Analysis and Design Steps

• OO Analysis: Identify and describe objects with responsibilities
• OO Design: Join objects based on intended associations
• OO Implementation: Implement the design using OO languages like C++ or Java