Introduction to Java Programming: Classes, Objects, Methods, and Syntax

When considering a Java program, it consists of objects communicating by invoking each other's methods. Let's delve into the concepts of classes, objects, methods, and instance variables:

• Object - Objects in Java encapsulate states (e.g., color, name, breed) and behaviors (e.g., wagging, barking, eating). Each object is an instance of a class.
• Class - A class serves as a blueprint or template defining the behaviors and states that objects of its type support.
• Methods - Methods represent the behaviors of a class. They contain the logic, manipulate data, and execute actions within a program.
• Instance Variables - Every object possesses its own set of instance variables. These variables determine the state of an object by holding assigned values.

First Java Program:

Let's start with a simple Java program that prints "Hello World".

public class MyFirstJavaProgram {

    public static void main(String[] args) {
       System.out.println("Hello World");
    }
}
      

To compile and run the program, follow these steps:

• Open a text editor (e.g., Notepad) and enter the code above.
• Save the file as MyFirstJavaProgram.java.
• Open a command prompt, navigate to the directory where the file is saved (e.g., C:\), and compile the code with javac MyFirstJavaProgram.java.
• If there are no errors, run the program with java MyFirstJavaProgram.
• You should see "Hello World" printed on the console.

Basic Syntax:

Key points to remember about Java syntax:

• Case Sensitivity - Java is case-sensitive, distinguishing between Hello and hello.
• Class Names - Begin with an uppercase letter; use uppercase for each inner word. Example: MyFirstJavaClass.
• Method Names - Begin with a lowercase letter; use uppercase for each inner word. Example: public void myMethodName().
• Program File Name - Must match the class name exactly. Save as MyFirstJavaProgram.java.
• public static void main(String args[]) - Entry point for Java programs; must be included in every Java application.