Describe the structure of a typical java program?

Question: Describe the structure of a typical java program?

In this blog post, we will describe the structure of a typical Java program. A Java program is composed of several elements, such as:

- **Documentation section**: This is an optional section that contains information about the program, such as the author, date, version, description, etc. It uses comments to write the documentation, which are ignored by the compiler. For example:

/**

 * This is a documentation comment

 * Author: John Doe

 * Date: 22/12/2023

 * Version: 1.0

 */

- **Package declaration**: This is an optional section that specifies the package name of the class. A package is a collection of related classes and interfaces that are organized in a hierarchical manner. A package declaration must be the first statement in a Java program, before any class or interface declaration. It uses the keyword package to declare the package name. For example:

package com.example; // where com is the root directory and example is the subdirectory

- **Import statements**: These are optional statements that allow us to use classes and interfaces from other packages without specifying their full names. They use the keyword import to import a specific class or all classes from a particular package. They are written after the package declaration and before the class or interface declaration. For example:

import java.util.Scanner; // imports the Scanner class from the java.util package

import java.io.*; // imports all classes from the java.io package

- **Class definition**: This is a mandatory section that defines the blueprint of an object. A class contains data members (variables) and member functions (methods) that describe the state and behavior of an object. A class definition uses the keyword class followed by the class name and a pair of curly braces. For example:

class HelloWorld { // defines a class named HelloWorld

  // data members and methods go here

}

- **Interface section**: This is an optional section that defines a contract or a set of rules that a class must follow. An interface contains only abstract methods (without implementation) and constants (final variables). An interface definition uses the keyword interface followed by the interface name and a pair of curly braces. For example:

interface Shape { // defines an interface named Shape

  // constants and abstract methods go here

}

- **Main method**: This is a special method that acts as the entry point of a Java program. It is executed by the Java Virtual Machine (JVM) when we run a Java program. The main method has a fixed signature: it is public, static, void, and accepts a String array as a parameter. The main method contains the logic of the program. For example:

public static void main(String[] args) { // defines the main method

  // program logic goes here

}

- **Class methods and behaviors**: These are optional sections that define the actions or operations that a class can perform. A method is a block of code that performs a specific task and can be reused. A method definition consists of a method header (name, parameters, return type, modifiers) and a method body (statements). For example:

public int add(int x, int y) { // defines a method named add

  // method body goes here

  return x + y; // returns the sum of x and y

}

To illustrate these elements, let us write a simple Java program that prints "Hello World" to the standard output.

// Documentation section

/**

 * This program prints "Hello World" to the standard output

 * Author: Jane Doe

 * Date: 22/12/2023

 * Version: 1.0

 */

// Package declaration

package com.example;

// Import statements

import java.io.PrintStream;

// Class definition

class HelloWorld {

  // Main method

  public static void main(String[] args) {

    // Create an object of PrintStream class

    PrintStream out = System.out;

    // Print "Hello World" to the standard output

    out.println("Hello World");

  }

}