Basic Syntax of Java

Welcome back, Java enthusiasts! Now that you’ve set up your development environment and written your first Java program, it’s time to dive deeper into the basics. Understanding the syntax is crucial as it forms the foundation of your coding skills. In this article, we’ll cover the basic syntax of Java, including data types, variables, operators, and control statements. Let’s get started!

Basic Structure of a Java Program

Every Java program consists of one or more classes, and each class can contain fields (variables) and methods (functions). The entry point of any Java program is the main method.

Here’s a quick refresher on the “Hello, World!” program to illustrate the structure:

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

• Class Declaration: public class HelloWorld declares a class named HelloWorld.
• Main Method: public static void main(String[] args) is the entry point of the program. The main method must be public, static, and return void.
• Statements: Inside the main method, we have a statement: System.out.println("Hello, World!"); which prints the text to the console.

Comments

Comments are ignored by the compiler but are useful for documenting your code.

• Single-line Comment: Use // for single-line comments.
• Multi-line Comment: Use /* ... */ for comments that span multiple lines.
• Documentation Comment: Use /** ... */ to create documentation comments that can be used by tools like Javadoc.

// This is a single-line comment

/*
 This is a 
 multi-line comment
*/

/**
 * This is a documentation comment
 * for the class HelloWorld.
 */

Data Types

Java is a strongly typed language, which means every variable must have a declared type. Java has two main categories of data types:

1. Primitive Data Types: byte, short, int, long, float, double, char, boolean
2. Reference Data Types: Objects, Arrays

Here’s an example demonstrating the use of different data types:

public class DataTypesExample {
    public static void main(String[] args) {
        int number = 10; // integer
        double price = 19.99; // double
        char letter = 'A'; // character
        boolean isJavaFun = true; // boolean

        System.out.println("Number: " + number);
        System.out.println("Price: " + price);
        System.out.println("Letter: " + letter);
        System.out.println("Is Java Fun? " + isJavaFun);
    }
}

Variables

Variables are containers for storing data values. In Java, you need to declare a variable before you can use it. A variable declaration includes the type and the name of the variable.

int age; // Declaration
age = 25; // Initialization

int year = 2024; // Declaration and Initialization

Operators

Operators are special symbols that perform specific operations on one, two, or three operands and then return a result. Here are some common types of operators:

• Arithmetic Operators: +, -, *, /, %
• Relational Operators: ==, !=, >, <, >=, <=
• Logical Operators: &&, ||, !
• Assignment Operators: =, +=, -=, *=, /=, %=

Example:

public class OperatorsExample {
    public static void main(String[] args) {
        int a = 10;
        int b = 5;

        // Arithmetic Operators
        System.out.println("a + b = " + (a + b));
        System.out.println("a - b = " + (a - b));
        System.out.println("a * b = " + (a * b));
        System.out.println("a / b = " + (a / b));
        System.out.println("a % b = " + (a % b));

        // Relational Operators
        System.out.println("a == b: " + (a == b));
        System.out.println("a != b: " + (a != b));
        System.out.println("a > b: " + (a > b));
        System.out.println("a < b: " + (a < b));
        System.out.println("a >= b: " + (a >= b));
        System.out.println("a <= b: " + (a <= b));

        // Logical Operators
        boolean x = true;
        boolean y = false;
        System.out.println("x && y: " + (x && y));
        System.out.println("x || y: " + (x || y));
        System.out.println("!x: " + (!x));
    }
}

Control Statements

Control statements allow you to control the flow of your program. The main control statements in Java are:

• If-Else: Conditional execution
• Switch: Multiple conditional branches
• For Loop: Repeated execution with a known number of iterations
• While Loop: Repeated execution while a condition is true
• Do-While Loop: Similar to while loop but checks the condition after executing the block

Examples:

public class ControlStatementsExample {
    public static void main(String[] args) {
        int number = 10;

        // If-Else
        if (number > 0) {
            System.out.println("Positive number");
        } else {
            System.out.println("Negative number or zero");
        }

        // Switch
        int day = 3;
        switch (day) {
            case 1:
                System.out.println("Monday");
                break;
            case 2:
                System.out.println("Tuesday");
                break;
            case 3:
                System.out.println("Wednesday");
                break;
            default:
                System.out.println("Other day");
                break;
        }

        // For Loop
        for (int i = 1; i <= 5; i++) {
            System.out.println("Iteration " + i);
        }

        // While Loop
        int i = 1;
        while (i <= 5) {
            System.out.println("Iteration " + i);
            i++;
        }

        // Do-While Loop
        int j = 1;
        do {
            System.out.println("Iteration " + j);
            j++;
        } while (j <= 5);
    }
}

Conclusion

Understanding the basic syntax of Java is the first step in becoming proficient in the language. In this article, we’ve covered the structure of a Java program, comments, data types, variables, operators, and control statements. Practice writing and running simple programs to reinforce these concepts.

Next up: We’ll explore Java’s object-oriented programming features, such as classes, objects, inheritance, and polymorphism. Stay tuned and happy coding!