Java Syntax & Structure – Java Fundamentals

Before diving into object-oriented programming or advanced features, it’s essential to understand Java’s basic syntax and program structure.

This foundation helps you read, write, and organize Java code properly.

What is Java Syntax?

• Syntax means the rules and structure that define how Java code must be written so the compiler can understand it.
• Java syntax is strict but readable, inspired by C and C++.
• Every Java program follows a clear, organized structure consisting of classes, methods, and statements.

Basic Structure of a Java Program

Here’s a simple example:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Welcome to Java!");
    }
}

Breakdown:

Key Syntax Rules

1. Case Sensitivity:

   Java is case-sensitive.

   → MyClass and myclass are different identifiers.

2. Class Names:

   Always start with an uppercase letter.

   Example: Student, BankAccount.

3. Method Names:

   Use camelCase convention.

   Example: calculateTotal(), getUserName().

4. File Name Rule:

   File name must match the public class name.

   → Class HelloWorld → File HelloWorld.java

5. Main Method Requirement:

   The main() method is mandatory to execute a Java program.

   Copy

   public static void main(String[] args)
   

6. Statements End with Semicolons:

   Every executable statement ends with ;

7. Comments:

   Used for notes or documentation (ignored by compiler).

   Copy

   // Single-line comment
   /* Multi-line
      comment */
   

Common Elements of Java Programs

Example: Program with Package & Import

package basics;

import java.util.Scanner;

public class InputExample {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter your name: ");
        String name = sc.nextLine();
        System.out.println("Hello, " + name + "!");
        sc.close();
    }
}

Here,

• package basics; → Groups the class inside a package named “basics”
• import java.util.Scanner; → Imports the Scanner class from Java’s library
• Scanner → Used to take input from the user

Whitespace & Indentation

• Java ignores extra spaces, tabs, and newlines.
• But indentation makes your code more readable and professional.

Example (Good Practice ):

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

Example (Bad Practice ):

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

Summary

🏆 Top 5 Java Interview Questions - Syntax & Structure

1. What is the structure of a basic Java program?

Answer: Every Java program is built around classes and methods, following a defined structure.

Example:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello Java!");
    }
}

Explanation:

• public class HelloWorld → Defines the class (must match file name).
• { ... } → Encloses class and method body.
• public static void main(String[] args) → Entry point of the program.
• System.out.println() → Prints output to the console.
• ; → Marks the end of a statement.

2. Why is the main() method important in Java?

Answer: The main() method acts as the entry point for Java applications.

When you run a Java program, the JVM looks for this method to begin execution.

Syntax:

public static void main(String[] args)

Explanation:

• public → Accessible to JVM from anywhere.
• static → Can be executed without creating an object.
• void → Does not return any value.
• String[] args → Accepts command-line arguments.

Without this method, the program cannot execute and throws an error.

3. What are Java naming conventions and why are they important?

Answer: Naming conventions make Java code readable, organized, and standardized across teams.

Java is case-sensitive → MyClass ≠ myclass.

Following these conventions improves code clarity and reduces errors.

4. What is the rule for class name and file name in Java?

Answer: If a class is declared public, the file name must match the class name exactly (including case).

Example (Correct):

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

File name → Hello.java

Incorrect Example:

public class Hello { }  //  File name: Test.java → Compilation Error

This rule ensures the compiler can locate and link the correct class.

5. Why are semicolons required in Java statements?

Answer: In Java, the semicolon (;) is used to end executable statements.

It tells the compiler where one instruction ends and the next begins.

Example:

System.out.println("Hello Java!");  //  Correct
System.out.println("Welcome")       //  Missing semicolon → Error

Without semicolons, the compiler cannot parse the code correctly, resulting in a syntax error.