Logical Operators in Java – AND, OR and NOT with Examples

public class LogicalBasics {
    public static void main(String[] args) {
        int age = 22;
        boolean hasId = true;
        boolean isVip = false;

        boolean canEnter = age >= 18 && hasId;          // AND: both must be true
        boolean freeDrink = isVip || age < 25;          // OR: at least one must be true
        boolean mustPay = !isVip;                       // NOT: flips the value

        System.out.println("canEnter  = " + canEnter);
        System.out.println("freeDrink = " + freeDrink);
        System.out.println("mustPay   = " + mustPay);

        // Combining operators (use parentheses for clarity)
        boolean discount = (age < 25 || isVip) && hasId;
        System.out.println("discount  = " + discount);
    }
}

public class ShortCircuit {
    static boolean check(String name, boolean result) {
        System.out.println("  evaluated " + name);
        return result;
    }

    public static void main(String[] args) {
        System.out.println("false && ...");
        boolean a = check("left", false) && check("right", true);   // right side skipped
        System.out.println("result: " + a);

        System.out.println("true || ...");
        boolean b = check("left", true) || check("right", false);   // right side skipped
        System.out.println("result: " + b);

        System.out.println("false & ... (no short-circuit)");
        boolean c = check("left", false) & check("right", true);    // both sides run
        System.out.println("result: " + c);

        // Practical use: a null check protects the method call
        String input = null;
        if (input != null && !input.isBlank()) {
            System.out.println("Got input");
        } else {
            System.out.println("No input (and no NullPointerException)");
        }
    }
}

public class ConditionRules {
    public static void main(String[] args) {
        boolean raining = true, haveUmbrella = false;

        // De Morgan's laws: !(A && B) == !A || !B   and   !(A || B) == !A && !B
        System.out.println("!(raining && haveUmbrella) = " + !(raining && haveUmbrella));
        System.out.println("!raining || !haveUmbrella  = " + (!raining || !haveUmbrella));

        // XOR on booleans: true when exactly one is true
        boolean cardPayment = true, cashPayment = false;
        System.out.println("exactly one payment method: " + (cardPayment ^ cashPayment));

        // && binds tighter than ||
        boolean x = true || false && false;      // true || (false && false)
        boolean y = (true || false) && false;
        System.out.println("true || false && false   = " + x);
        System.out.println("(true || false) && false = " + y);

        // Range check
        int score = 75;
        System.out.println("score in 60..100: " + (score >= 60 && score <= 100));
    }
}