Java Introduction

Java is versatile, high level and widely used programming language and independent platform.

Oracle has since continued to maintain and develop the java platform.

Java is developed by in 1995  and java is most popular programming language.

Why Use Java?

    • Java is platform independent.

    • Once write a java code that code run anywhere or different platforms.

    • Java is easy to use.

    • It is easy to learn.

    • Java is secure, fast and powerful language.

    • Java is widely used Programming language for web applications.

    • Java’s strong support for object-oriented programming encourages code organization, reusability, and maintainability.

    • Java can be used for desktop, web, mobile, and server-side applications.

    • Java is built-in support for multithreading is valuable for developing parallel applications.

    • It has large community support.

    • java offers a wide range of libraries, frameworks, and tools for diverse application domains.

 Java Application

    • Web Applications

    • Mobile Applications

    • Enterprise Applications

    • Desktop Applications

    • Gaming

    • Robotics

    • E-commerce Platforms

    • Networking and Communication

    • Embedded Systems

    • Cloud-Based Applications

    • Educational Software

    • Social Media Platforms

    • Healthcare Applications

    • Financial and Banking Portals

    • Government and Public Services

Program Structure of  Java

// Class Declaration: Every Java program starts with a class declaration.
public class Example {

// Main Method: The main method is the entry point of the program.
// It has a specific signature with “public static void main(String[] args)”.
         public static void main(String[] args) {

// Output Statement: This statement prints “Hello World” to the console.
                 System.out.println(“Hello,  World!”); // This is a comment at the end of the line.



Java Comments

In Java, comments are used to provide explanations and documentation within the code. They are not executed as part of the program and are ignored by the Java compiler.

There are three types of comments in java:

1. Single-line Comment:

  • Single-line comments are used to add comments on a single line. They start with // and continue to the end of the line.


// This is a single-line comment
int x = 10;  // You can also add a comment at the end of a line of code 

2. Multi-line Comment:

  • Multi-line comments are used to comment multiple lines of code. They start with /* and end with */. Anything between these delimiters is considered a comment.


/* This is a multi-line comment.
It can span multiple lines and is often used for longer explanations. */
int a = 10;  

3. Javadoc Comment:

  • Javadoc comments are a special type of comment used for generating documentation. They start with /** and end with */. Javadoc comments can include special tags to document classes, methods, fields, and more.


 * This is a Javadoc comment for the MyClass class.
 * It provides an overview of the class’s purpose and usage.
 * You can add detailed explanations, author information, and more here.
public class MyClass {
    // Class members and methods go here

Java Advantages and Disadvantages


  • Platform Independence: Code written in Java can be executed on any platform with a Java Virtual Machine (JVM), making it highly portable.
  • Simple: Java is simple programming language since it is easy to learn easy to understand. 
  • Object-Oriented: Java is a pure object-oriented programming language, promoting modularity and code reusability.
  • Multithreading Support: Java offers built-in support for multithreading, allowing the development of concurrent and parallel applications.
  • Scalability: Java can be used for building small applications and large enterprise-level systems.
  • Security Features: Java is a secured programming language. Java incorporates various security features, such as a classloader to separate different classes, and the “sandbox” for executing untrusted code.
  • Robust: Java includes error-checking at various stages of development, helping developers write reliable and bug-free code.


  • Performance Overhead: While Java has improved over the years, it may still be slower than languages like C or C++. This is due to the overhead of the JVM and the automatic memory management.
  • Memory Consumption: Java applications tend to consume more memory compared to applications written in languages with manual memory management.
  • Limited GUI Support: Although Java has GUI libraries like Swing and JavaFX, it may not be the first choice for building modern, high-performance graphical applications compared to some other technologies.
  • Multithreading Complexity: While Java supports multithreading, writing correct and efficient multithreaded code can be complex and error-prone.
  • Interpreter Overhead: The JVM’s initial startup time and runtime execution can introduce some overhead, especially for very short-lived applications.
  • Limited Low-Level Access: For low-level system operations, Java is less suitable than languages like C or C++.