About Lesson
Introduction to Java
Introduction to Java and its history
Setting up the Java environment (JDK, IDE)
Writing and running a "Hello World" program
Basic data types and variables
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Operators and Expressions
Java Operators
Operators are used to perform operations on variables and values.
In the example below, we use the + operator to add together two values:
ExampleGet your own Java Server
int x = 100 + 50;
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Control Flow Statements
Control flow statements are statements in Java that control the order in which other statements are executed. They allow you to specify the sequence in which statements are executed based on certain conditions. There are three types of control flow statements in Java: if-else statements, switch statements, and loops.
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Arrays
In Java, an array is an object that stores a fixed-size sequential collection of elements of the same type. Each element in an array is identified by an index, which is a non-negative integer value that represents its position in the array.
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Object-Oriented Programming Basics
Object-oriented programming (OOP) is a programming paradigm that focuses on creating software components called objects, which encapsulate data and behavior. In OOP, you define classes that serve as blueprints for creating objects, and you create objects by instantiating these classes.
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OOP Concepts
Object-oriented programming (OOP) is a programming paradigm that focuses on creating software components called objects, which encapsulate data and behavior. OOP is based on several fundamental concepts, including:
Encapsulation: Encapsulation is the process of hiding the internal details of an object from the outside world, and exposing only the necessary information and functionality through a public interface. This helps to ensure that the object's internal state remains consistent and secure.
Inheritance: Inheritance is a mechanism that allows a class to inherit properties and methods from another class. The class that is being inherited from is called the superclass or base class, and the class that is inheriting is called the subclass or derived class. This helps to avoid code duplication and promote code reuse.
Polymorphism: Polymorphism is the ability of an object to take on multiple forms. In Java, this is achieved through method overloading and method overriding. Method overloading allows you to define multiple methods with the same name but different parameter lists, while method overriding allows a subclass to provide its own implementation of a method that is already defined in the superclass.
Abstraction: Abstraction is the process of representing complex real-world entities using simpler and more abstract concepts. In OOP, this is achieved by defining abstract classes and interfaces that provide a common set of methods and properties that can be used by multiple subclasses.
Composition: Composition is the process of creating complex objects by combining simpler objects. In OOP, this is achieved by creating objects that contain other objects as instance variables.
These concepts are closely related and work together to create a powerful and flexible programming paradigm. By using OOP concepts effectively, you can create more maintainable, reusable, and extensible code that is easier to understand and modify.
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Exception Handling
Exception handling is a mechanism in Java that allows you to handle errors and other exceptional situations in your code. When an exception is thrown, Java looks for an appropriate exception handler to handle the exception and prevent the program from crashing.
In Java, exceptions are represented by objects that are subclasses of the Throwable class. There are two types of exceptions in Java: checked exceptions and unchecked exceptions. Checked exceptions are exceptions that must be declared in the method signature, and must be handled or propagated to the calling method. Unchecked exceptions, on the other hand, do not have to be declared or caught, and can propagate up the call stack until they are handled by an appropriate exception handler.
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