Methods

public class MethodBasics {
    // Method with no parameters, no return value
    static void printSeparator() {
        System.out.println("========================");
    }

    // Method with parameters and return value
    static int add(int a, int b) {
        return a + b;
    }

    // Method that returns a String
    static String getGreeting(String name) {
        return "Hello, " + name + "!";
    }

    public static void main(String[] args) {
        printSeparator();
        System.out.println(getGreeting("Tester"));
        printSeparator();

        int sum = add(10, 20);
        System.out.println("Sum: " + sum);
    }
}

========================
Hello, Tester!
========================
Sum: 30

public class MethodParams {
    // No parameters
    static String getBaseUrl() {
        return "https://demo-bank.example.com";
    }

    // One parameter
    static boolean isValidEmail(String email) {
        return email.contains("@") && email.contains(".");
    }

    // Multiple parameters
    static String buildUrl(String base, String path, int id) {
        return base + "/" + path + "/" + id;
    }

    public static void main(String[] args) {
        System.out.println(getBaseUrl());
        System.out.println(isValidEmail("user@test.com"));  // true
        System.out.println(isValidEmail("invalid"));        // false

        String url = buildUrl("https://api.example.com", "users", 42);
        System.out.println(url);  // https://api.example.com/users/42
    }
}

public class Overloading {
    // Log with message only
    static void log(String message) {
        System.out.println("[INFO] " + message);
    }

    // Log with level and message
    static void log(String level, String message) {
        System.out.println("[" + level + "] " + message);
    }

    // Log with level, message, and test name
    static void log(String level, String testName, String message) {
        System.out.println("[" + level + "] " + testName + " — " + message);
    }

    public static void main(String[] args) {
        log("Test started");
        log("WARN", "Slow response detected");
        log("ERROR", "LoginTest", "Element not found");
    }
}

[INFO] Test started
[WARN] Slow response detected
[ERROR] LoginTest — Element not found

public class Scope {
    static int classLevel = 100;  // accessible everywhere in this class

    static void demo() {
        int methodLevel = 50;  // accessible only in this method
        System.out.println(classLevel);   // OK
        System.out.println(methodLevel);  // OK

        if (true) {
            int blockLevel = 25;  // accessible only in this if block
            System.out.println(blockLevel);   // OK
            System.out.println(methodLevel);  // OK
        }

        // System.out.println(blockLevel);  // ERROR — out of scope
    }

    public static void main(String[] args) {
        demo();
        System.out.println(classLevel);    // OK
        // System.out.println(methodLevel);  // ERROR — out of scope
    }
}

public class TestHelpers {
    static boolean isEven(int number) {
        return number % 2 == 0;
    }

    static boolean isPalindrome(String text) {
        String cleaned = text.toLowerCase().replaceAll("[^a-z0-9]", "");
        String reversed = new StringBuilder(cleaned).reverse().toString();
        return cleaned.equals(reversed);
    }

    static String maskPassword(String password) {
        if (password.length() <= 2) return "**";
        return password.charAt(0) + "*".repeat(password.length() - 2) + password.charAt(password.length() - 1);
    }

    static int countOccurrences(String text, char target) {
        int count = 0;
        for (int i = 0; i < text.length(); i++) {
            if (text.charAt(i) == target) {
                count++;
            }
        }
        return count;
    }

    public static void main(String[] args) {
        System.out.println(isEven(4));                 // true
        System.out.println(isPalindrome("racecar"));   // true
        System.out.println(isPalindrome("hello"));     // false
        System.out.println(maskPassword("Test@123"));  // T******3
        System.out.println(countOccurrences("hello world", 'l'));  // 3
    }
}