Java Syntax

Syntax means the rules of writing code. Java has strict rules, and the compiler tells you when you break one. Here are the most important ones.

A Java program

public class Main {                                  // class
    public static void main(String[] args) {        // method
        int age = 20;                                // statement
        System.out.println("Age: " + age);          // statement
    }
}

The rules

• All code is inside a class. (Java 25 compact files are an exception for small programs.)
• A statement ends with a semicolon ;.
• Blocks use curly braces { }. A block groups many statements, like the body of a method or a loop.
• Java is case sensitive. name, Name and NAME are three different names.
• The file name must match the public class name, and the file ends with .java.
• Spaces and new lines do not matter, but good formatting makes the code easy to read.

Identifiers

An identifier is a name you give to a variable, method or class. The rules:

• It can have letters, digits, _ and $.
• It cannot start with a digit.
• It cannot be a keyword like class, int or for.
• It has no spaces.

public class Names {
    public static void main(String[] args) {
        int 2nd = 5;
    }
}

Naming conventions

What	Style	Example
Class, interface, record, enum	PascalCase	StudentRecord
Method, variable	camelCase	totalMarks, getName()
Constant	UPPER_SNAKE_CASE	MAX_SIZE
Package	all small letters	com.example.shop

Statements and blocks

public class Blocks {
    public static void main(String[] args) {
        int marks = 72;
        if (marks >= 40) {            // a block starts
            System.out.println("Pass");
            System.out.println("Well done");
        }                             // a block ends
    }
}

Keywords

Java has about 50 reserved words, such as class, public, static, if, else, for, while, return, new, try and catch. You cannot use them as names. You will learn them step by step in this tutorial.

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