Java — Ternary Expressions & String Comparisons (.equals vs ==)

import java.util.Objects;

public class Main {
    public static void main(String[] args) {
        // 1. Ternary Operator Demonstration
        int userAge = 20;
        String eligibility = (userAge >= 18) ? "Eligible for Driving License" : "Underage";
        System.out.println("Age Check: " + eligibility);

        // 2. String Equality (.equals vs ==)
        String roleFromAuthToken = "SUPER_ADMIN";
        String roleFromDatabase  = new String("SUPER_ADMIN");

        System.out.println("
--- String Comparison Deep Dive ---");
        System.out.println("Using == (Memory Address Check) : " + (roleFromAuthToken == roleFromDatabase)); // false
        System.out.println("Using .equals() (Content Check) : " + roleFromAuthToken.equals(roleFromDatabase)); // true

        // 3. Case-Insensitive Comparison
        String inputCoupon = "save20";
        String validCoupon = "SAVE20";
        boolean isCouponValid = inputCoupon.equalsIgnoreCase(validCoupon);
        System.out.println("Coupon Validation (IgnoreCase)  : " + isCouponValid);

        // 4. Null-Safe Comparison
        String nullableRole = null;
        // System.out.println(nullableRole.equals("ADMIN")); // Throws NullPointerException!
        boolean isSafeAdmin = "ADMIN".equalsIgnoreCase(nullableRole); // Safe!
        System.out.println("Null-Safe Admin Check (Yoda)    : " + isSafeAdmin);
    }
}

Age Check: Eligible for Driving License

--- String Comparison Deep Dive ---
Using == (Memory Address Check) : false
Using .equals() (Content Check) : true
Coupon Validation (IgnoreCase)  : true
Null-Safe Admin Check (Yoda)    : false

public class LoginAuthenticationService {
    public static void main(String[] args) {
        String registeredUser = "BalajiNayak";
        String enteredUsername = "balajinayak";
        String enteredPassword = "Password@2026";
        String correctPassword = "Password@2026";

        // Username should be case-insensitive, Password MUST be strictly case-sensitive
        boolean isUsernameMatch = registeredUser.equalsIgnoreCase(enteredUsername);
        boolean isPasswordMatch = correctPassword.equals(enteredPassword);

        if (isUsernameMatch && isPasswordMatch) {
            System.out.println("✓ Login Successful! Welcome, " + registeredUser);
        } else if (!isUsernameMatch) {
            System.out.println("✗ Login Failed: Username not found!");
        } else {
            System.out.println("✗ Login Failed: Invalid password provided!");
        }
    }
}