Java Syntax
Understanding Java language rules and structure
📝 Java Syntax Rules
Java syntax defines the rules for writing Java programs. It includes proper structure, naming conventions, keywords, and punctuation that make your code readable and executable.
// Basic Java syntax example
public class SyntaxExample {
public static void main(String[] args) {
String message = "Learning Java syntax!";
System.out.println(message);
}
}
Output:
Learning Java syntax!
Key Syntax Elements
Class Declaration
Every Java program starts with a class
public class MyClass {
// code here
}Main Method
Entry point of Java programs
public static void main(String[] args) {
// program starts here
}Semicolons
End every statement with semicolon
int age = 25;
String name = "John";Curly Braces
Define code blocks and scope
if (condition) {
// code block
}🔹 Java Program Structure
Every Java program follows this basic structure:
// 1. Package declaration (optional)
package com.example;
// 2. Import statements (optional)
import java.util.Scanner;
// 3. Class declaration (required)
public class ProgramStructure {
// 4. Class variables (optional)
static String appName = "My App";
// 5. Main method (required for executable programs)
public static void main(String[] args) {
// 6. Local variables
int number = 42;
String text = "Hello Java";
// 7. Program logic
System.out.println(appName);
System.out.println(text + " " + number);
}
}Output:
My App
Hello Java 42
🔹 Naming Conventions
Java follows specific naming rules:
🔸 Classes
Use PascalCase (first letter uppercase)
public class StudentRecord { }
public class BankAccount { }
public class CarEngine { }🔸 Variables and Methods
Use camelCase (first letter lowercase)
int studentAge = 20;
String firstName = "John";
double accountBalance = 1500.50;
public void calculateTotal() { }
public String getUserName() { }🔸 Constants
Use UPPER_CASE with underscores
final int MAX_SIZE = 100;
final String DATABASE_URL = "localhost";
final double PI = 3.14159;🔹 Comments in Java
Use comments to explain your code:
// Single-line comment
// This explains what the next line does
/*
* Multi-line comment
* Used for longer explanations
* Can span multiple lines
*/
/**
* Documentation comment (Javadoc)
* Used to generate API documentation
* @param args command line arguments
*/
public static void main(String[] args) {
int age = 25; // Variable to store age
/*
* Print welcome message
* This is visible to users
*/
System.out.println("Welcome! You are " + age + " years old.");
}Output:
Welcome! You are 25 years old.
🔹 Case Sensitivity
Java is case-sensitive - capitalization matters:
❌ These are different:
String name = "John";
String Name = "Jane"; // Different variable
String NAME = "Bob"; // Different variable
// Method names are also case-sensitive
System.out.println(); // Correct
system.out.println(); // Error - 'system' not found✅ Be consistent:
String firstName = "John";
String lastName = "Doe";
String fullName = firstName + " " + lastName;
System.out.println(fullName);🔹 Java Keywords
Reserved words that have special meaning: