java_crazies

/** Crazy 1 */

import java.util.ArrayList;

public class Crazy1 {

    // Props to:
    // - https://stackoverflow.com/questions/15496/hidden-features-of-java
    // - Java Puzzlers (Joshua Bloch)
    
    public static void main(String[] args) {
        // Double brace initialization
        // http://wiki.c2.com/?DoubleBraceInitialization
        
        var validCodes = new ArrayList<String>() {{
            add("HOW");
            add("IS");
            add("THIS");
            add("WORKING");
        }};
        validCodes.forEach(System.out::println);

    }
}


/** Crazy 2 */
import java.util.Collection;

public class Crazy2 {

    // Joint union in type parameter variance
    public static <A, B extends Collection<A> & Comparable<B>> boolean foo(B b1, B b2, A a) {
        return (b1.compareTo(b2) == 0) || b1.contains(a) || b2.contains(a);
     }
     
    public static void main(String[] args) {
        System.out.println("Yes");
    }
}

/** Crazy 3 */
interface Room {
    public Room north();
    public Room south();
    public Room east();
    public Room west();
}

// Use enum to implement an interface
enum Rooms implements Room {
    FIRST {
       public Room north() {
          return SECOND;
       }
    },
    SECOND {
       public Room south() {
          return FIRST;
       }
    };
 
    public Room north() { return null; }
    public Room south() { return null; }
    public Room east() { return null; }
    public Room west() { return null; }
 }


public class Crazy3 {
    public static void main(String[] args) {
        System.out.println(Rooms.FIRST.north());
    }
}


/** Crazy 4 */

public class Crazy4 {
    public static void main(String[] args) {
        // Can the next row be valid??? IDE says no!
        http://www.google.com
        System.out.println("Another odd thing");
    }
}


/** Crazy 5 */
public class Crazy5 {
    public static void main(String[] args) {

        System.out.println("Let's do some basic math! Is 1 == 1? Is 128 == 128?");

        // Boxing/Unboxing + Integer pool oddities

        var a = 1;
        var b = 1;
        var c = Integer.valueOf(1);
        var d = Integer.valueOf(1);
        var e = new Integer(1);
        var f = new Integer(1);

        Integer g = 128;
        Integer h = 128;

        System.out.printf("Is %s same as %s? %s%n",a, b, a == b);   
        System.out.printf("Is %s same as %s? %s%n",a, c, a == c);   
        System.out.printf("Is %s same as %s? %s%n",c, d, c == d);   
        System.out.printf("Is %s same as %s? %s%n",a, e, a == e);   
        System.out.printf("Is %s same as %s? %s%n",e, f, e == f);   
        System.out.printf("Is %s same as %s? %s%n",g, h, g == h);   

    }
}

/** Crazy 6 */
// This needs to be run from the command line
public class Crazy6{static{System.out.print("ONELINER");System.exit(0);}}

/** Crazy 7 */
public class Crazy7 {
    public static void main(String[] args) {
        // Variable names are defined to be perhaps more flexible than you think...
        var $ = "THIS IS OKAY!";
        var \u0223 = "\u0223THIS IS OKAY TOO!";
        System.out.printf("Yeah, I can live with these%n%s%n%s%n", $, \u0223);
        System.out.println("Okay, still please don't use these! :)");
    }
}

/** Crazy 8 */
import java.lang.reflect.Field;
import java.util.Calendar;
import java.util.Date;

public class Crazy8 {
    public static void main(String[] args) {
        var currentDate = new Date(2021,1,1);
        System.out.printf("Welcome to %s%n",currentDate);

        Calendar cal = Calendar.getInstance();
        cal.set(2021,12,31);
        System.out.println(cal.getTime());
    }
}

/** Crazy 9 */

import java.util.Random;

public class Crazy9 {
    public static void main(String... args) {

        // Are the random number generators really random? They are so random that
        // sometimes they are not random at all!
        // This party trick is here just here for no purpose, mathematically this is what you'd expect
        // Remember this the next time lottery numbers are generated!

        Random random = new Random(-6732303926L);
        for (int i = 0; i < 10; i++)
            System.out.print(random.nextInt(10) + " ");

        System.out.println("");

        System.out.println(randomString(-229985452) + ' ' + randomString(-147909649));

    }

    public static String randomString(int seed) {
        var rand = new Random(seed);
        var sb = new StringBuilder();
        for (int i = 0;; i++) {
            int n = rand.nextInt(27);
            if (n == 0)
                break;
            sb.append((char) ('`' + n));
        }
        return sb.toString();
    }

}

/** Crazy 10 */
public class Crazy10 {
    public static void main(String[] args) {
        
        // WHaaaaat witchcraftery is this?

        System.out.println((byte) + (char) - (int) + (long) - 1);
        
        String _‎ = "Hello "; String _‏ = "World"; String _‎‏ = " !!"; 
        
        System.out.println(_‎+_‏+_‎‏);
    }
}

/** Bonus Crazy */
import java.lang.reflect.Field;

public class Crazy11 {
    public static void main(String[] args) {
        System.out.println("Okay what's the output?"); 
    }


    


























    static {
        try {
            Field value = String.class.getDeclaredField("value");
            value.setAccessible(true);
            value.set("Okay what's the output?", value.get("Terveisiä peräseinäjoelta!"));
        } catch (Exception e) {
            throw new AssertionError(e);
        }
    }
}