Introduction to Java Programming

Java Basics

• Java is understood by knowing the reasons behind its creation.
• Computer language advancements happen for two main reasons: adapting to changing uses and improving programming.
• Java shares lineage with C++, which itself descends from C, inheriting characteristics from both.
• Java's syntax comes from C, while its object-oriented features are influenced by C++.
• Java's rise was driven by the need for platform-independent programs, especially for distribution over the Internet.
• Java improved upon object-oriented programming from C++, adding support for multithreading, and simplifying Internet access.
• Java innovated with applets, which are programs designed to be transmitted over the Internet and executed by web browsers.
• Servlets are small programs that execute on the server, extending web server functionality like applets do for web browsers.
• The Java compiler outputs bytecode, not executable code; bytecode is executed by the Java Virtual Machine (JVM).
• Key features include being simple, secure, portable, object-oriented, robust, multithreaded, architecture-neutral, interpreted, high-performance, distributed, and dynamic.

Evolution of Java: The Need for Simplicity

• C, developed in 1970, is limited in handling complexity as programs grow.
• C++ enhanced C by adding features for programmers to manage larger programs more easily.
• Bjarne Stroustrup invented C++ in 1979 at Bell Laboratories, initially calling it "C with Classes"; it was renamed C++ in 1983.
• C++ extends C with object-oriented features, yet retains all features, attributes, and benefits of C
• C++'s invention was to enhance the language rather than creating one

Core Principles of Object-Oriented Programming (OOP)

• Object-oriented programming (OOP) forms Java's foundation.
• All computer programs are constructed with code and data.
• Programs are built based on the process-oriented model which characterizes a program as a series of code.
• The process-oriented model views code acting on the data
• The object-oriented programming is created to manage complexity
• OOP organizes a program around its data (objects) with defined interfaces.
• OOP characterizes data controlling access to code.
• Abstraction is key element of OOP.
• Hierarchical classifications is the way to manage abstraction
• Abstraction can convert data from process-oriented programs into component objects.
• OOP languages provide mechanisms to implement OOP model: encapsulation, inheritance, and polymorphism.
• Each object exhibits unique behavior, acting as entities responding to messages.

OOP Concepts: Encapsulation, Inheritance, Polymorphism

• Encapsulation ensures data safety, protects code and data from misuse by binding manipulating code together
• Viewing encapsulation is a protective barrier that prevents other code freely accessing code and data
• Encapsulation is tightly controlled via a well defined interface.
• In Java, Class is the basis of encapsulation . Class describes the behavior and structure that will be shared amongst objects.
• Mechanisms are in place for managing complexities within classes; methods and variables can be designated as either private or public.
• The class's public interface outlines what external users should know.
• Only member code of a class can access private methods and data.
• Inheritance allows a single object to derive the features of another that supports hierarchical classification.
• With inheritance and encapsulation, a subclass gains the attributes of its parent class and builds upon it.
• Polymorphism enables one interface to handle a general class of actions, where the exact action depends on the situation.
• Polymorphism makes it possible for Java to define universal stack routines.

Writing Essential Java Programs

• For Java, the source file name is very important.
• Compile using the javac compiler, that makes the Example.class with bytecode.
• Java bytecode is a representation output which gets executed by JVM.
• Use java to actually run program since JVM is the application launcher.
• During Java compilation, each class is compiled into each separate file and stores in .class.
• Java requires naming the file to correlate with the class to match name to .class when it executes.
• When you execute java you are simply naming the class. Java name searches for the file with .class extension
• Comments are not part of java code

Key Elements of Java

• Use the keyword class inside the program to declare the new name as identifier.
• The main() method The public keyword acts as an access modifier
• If the class member has public class, the code outside can access the class
• Oppositely, the member cannot have a code that is outside if is private
• If main() is declared as public it should correlate by calling the code outside the class on startup of program
• Static code is required so that main() can be run, it does not need to instantiate
• The void keyword informs the compiler that the main() will not return a value
• Without a main() the Java will compile a program
• String args[] can pass parameters named args, that represent an array of strings
• System is a predefined java class that provides access and out is the output steam that displays the console

Contrasting OOP and POP

• In Procedure Oriented Programming (POP), large programs are split into smaller functions.
• In POP, these components are considered as a sequence of code.
• POP needs the function name to invoke the procedure.
• Data typically does not get much attention and importance in POP based functions
• The primary emphasis of POP is on the function/procedure itself and not the data it acts upon and procedures.
• Many critical data elements are made global in multi-function programs so that functions can use it and change accordingly.
• The program cannot identify the changes if data is global
• C programming language follows the procedural approach.
• Object-oriented programming (OOP) gives high importance of data being the focus.
• OOP protects data closely and the data function modification should be inside the function operation.
• OOP divides a problem into reusable entities or objects
• C++, Java, and Python are object oriented programming languages

Core Components of Java Execution

• JDK (Java Development Kit) is needed for develop and run Java programs; it comes with development tools, JRE.
• JRE (Java Runtime Environment) lets Java programs onto the machine .
• JVM(Java Virtual Machine) is a interpreter engine

Encapsulation Explained

• Wrapping the data is what the term encapsulation is intended to be and is in a class.
• Code manipulation, data, and binding of each other is due to what mechanism is that referred to as.
• A protective shield to prevent data code access is the thought of preventing data outside the code
• Data variable is in the encapsulation form.

Importance of Data Hiding

• The data of class should not accessible, data should only be accessible only through the same class
• The coding behind end user data should be hidden from outside world, but the abstract concept should still perform
• Hiding and abstraction concept should still be a combination to encapsulate the data.
• Setter and getter methods should be used to be encapsulated and to define.
• Data members should be encapsulated for restricted access in the code by hiding code details and implementing.
• Variable class can be read and changed according to the requirement to be more flexible
• Encapsulation should be re used to easy new change, and encapsulated should be tested by the unit.

How to use Modifiers in Java

• Modifiers can be divided into access and non access
• Access controls the JVM level.
• The non access control does not give level access

Access Modifiers in Java

• Either public or default can be implemented.
• All codes can access a data if public
• Only available classes can access data.

non access modifiers

• Final or abstract is either used

Introduction to Inheritance in Java

• By creating new class based on previous ones, it has its field.
• You can inherit by methods and fields class.
• Class hierarchical can be structured to use models of the world.
• Abstraction for abstraction class can be extracted to make the code organized.

Java's Polymorphism

• Polymorphism which translates to many forms,
• Displaying a display form shows ability.
• The word poly means many and morphs means form, so it means one of the term
• Compiled or runtime are mainly types that are used in polymorphism

Compiler and Runtime Polymorphism

• For static , it's function by method that is achieved.
• It will be ran on runtime.

Abstraction: Presenting Essentials

• Abstraction displays only the essence but never individual components.
• Data abstraction recognizes objects
• Interfaces abstract achieves java code abstraction.

Encapsulation vs Data Abstraction

• Data hiding to implement while in abstraction it doesn't show data
• The encapsulation class java follows high level procedure while abstraction is an implementation design
• 5 OOP consist is data hiding,abstraction, polymorphism,encapsulation, and inheritance

How to use Packages in Java

• Class, interface, subpackage is able is encapsulated.
• Packages are used for conflict name and help.
• Accessible level package is either default of other protected member.
• Data are encapsulation(data hiding)
• After class, packages are also used, then you import class for packages is also necessary
• packages can be reused, and package names are related on directory
• created in package directory
• Sub packages, not to be imported, is other specified, also members should not access,
• Types of packages are in use for program.

Using a Set of Packages

• Classes for example, data for lang
• Files can be read with java for example io, list etc
• Java applet for java, and swing buttons etc
• To create class and directory its the same for package names and first statement to include inside.

How Handling Exception works

• It's important to know, the cause of an error and know each user as the code
• Exception stops running after a certain amount, it has catch for exception is in thrown.
• If any problem is detected which can't be processed, a error will appear to fix the application
• Either have to be either catch and throw if caused an exemption to be thrown..