public class Hamlet {
    public static void main(String[] args) {
        Random rnd = new Random();
        boolean toBe = rnd.nextBoolean();
        Number result = (toBe || !toBe) ?
                new Integer(3) : new Float(1);
        System.out.println(result);
    }
}

public class Parsing {
    /**
     * Returns Integer corresponding to s, or null if s is null.
     * @throws NumberFormatException if s is nonnull and
     * doesn't represent a valid integer
     */
    public static Integer parseInt(String s) {
        return (s == null) ?
                (Integer) null : Integer.parseInt(s);
    }
    public static void main(String[] args) {
        System.out.println(parseInt("-1") + " " +
                parseInt(null) + " " +
                parseInt("1"));
    }
}

public class MyMap {

    public static void main(String[] args) {
        Map map = new IdentityHashMap<>();
        map.put(1, "Hello");
        map.putIfAbsent(1, "World");
        print(map.get(1));
        print(map.size());

        map.put(1024, "A");
        map.putIfAbsent(1024, "B");
        print(map.get(1024));
        print(map.size());

    }

    private static void print(Object object) {
        System.out.print(object + " ");
    }
}

public class IntegerChange {

    public static void main(String[] args) throws Exception {
        Integer a = Integer.parseInt("10");
        Integer b = Integer.valueOf(10);
        Integer c = 10;
        changeValue(a, 100);
        changeValue(b, 200);
        changeValue(c, 300);
        System.out.printf("%d %d %d", a, b, c);
    }

    private static void changeValue(Integer i, int value) throws Exception {
        Field field = Integer.class.getDeclaredField("value");
        field.setAccessible(true);
        field.set(i, value);
    }
}