Java Syntax

Java Syntax Fundamentals

In the previous chapter, we created our first Java program. Now, let's break down the fundamental syntax rules that you must follow when writing Java code. Understanding these rules is essential for writing code that the compiler can understand and execute.

The main Method

As we saw, the main method is the starting point for any Java program. Its signature is always the same:

public class Main {
  public static void main(String[] args) {
    // Your code goes here
    System.out.println("The main method is where execution begins.");
  }
}

Every Java program must have a main method inside a class.

Code Blocks and Curly Braces {}

In Java, a block of code is a group of zero or more statements that are enclosed in curly braces {}. These blocks define the scope of classes, methods, and control flow statements.

public class MyClass { // Start of class block

  public static void main(String[] args) { // Start of method block
    int x = 10;
    if (x > 5) { // Start of if-statement block
      System.out.println("x is greater than 5");
    } // End of if-statement block
  } // End of method block
} // End of class block

Statements and Semicolons ;

A statement is a single instruction that the Java compiler can execute. Every statement in Java must end with a semicolon ;. The semicolon tells the compiler that the statement is complete.

Forgetting a semicolon is one of the most common errors for beginners.

public class SemicolonExample {
  public static void main(String[] args) {
    // This is one statement
    System.out.println("Hello!");
    // This is another statement
    int myNumber = 100;
    // This is a third statement
    myNumber = myNumber + 50;
    System.out.println(myNumber);
  }
}

Java Naming Conventions

Java has established conventions for naming classes, methods, and variables to make code more readable.

• Class Names: Should start with an uppercase letter and follow the PascalCase convention (e.g., MyFirstClass, Car, String).
• Method Names: Should start with a lowercase letter and follow the camelCase convention (e.g., myMethodName(), calculateSum()).
• Variable Names: Should also start with a lowercase letter and use camelCase (e.g., userName, totalScore).
• File Name: The name of the Java file must exactly match the name of the public class inside it (e.g., class Main must be in a file named Main.java).

Java is case-sensitive, which means myVariable and MyVariable are treated as two different variables.