You win a prize if you correctly guess the output

Trick.java

import java.util.*;

public class Trick {

    public static void main(String args[]) {
    System.out.println("/////////////////////////////////////////////////");
    HashSet<Long> h = new HashSet();
    Long l = (long)4;
    h.add(l);
    System.out.println(h.contains(4));

    System.out.println("/////////////////////////////////////////////////");
    int x1 = (int)(20.02*100), x2 = (int)(2.002*1000), x3 = (int)200.2*10;
    System.out.println(x1 + " = " + x2 + " = " + x3);

    System.out.println("/////////////////////////////////////////////////");
    int x[] = {1,2,3};
    rotate1(x);
    System.out.println(Arrays.toString(x));
    rotate2(x);
    System.out.println(Arrays.toString(x));

    System.out.println("/////////////////////////////////////////////////");
    System.out.printf("%n", "hello world", "0k");
    System.out.printf("%s", "hello world\r", "ok");

    System.out.println("/////////////////////////////////////////////////");
    System.out.println(Math.atan(0/1) + " = " + Math.atan(-0/1) + " = " + Math.atan(-0./1) + " = " + Math.atan(-0/1.));
    System.out.println((Math.atan(-0./1) == Math.atan(0/1)) + "\n" +
                     (Math.atan(-0./1) < Math.atan(0/1)) + "\n" +
                           (1/Math.atan(-0./1) == 1/Math.atan(0/1)) + "\n" +
                           (1/Math.atan(-0./1) < 1/Math.atan(0/1)));

    System.out.println("/////////////////////////////////////////////////");
    ArrayList<String> as = new ArrayList<String>();
    HashSet hs = new HashSet<ArrayList>();
    hs.add(as);
    as.add("B8");
    System.out.println(hs.contains(as));
    hs.add(as);
    System.out.println(hs.contains(as));
    as.remove("B8");
    as.add("AW");
    System.out.println(hs.contains(as));

    System.out.println("/////////////////////////////////////////////////");
        //find a string that overflows int in its hascode

    System.out.println("/////////////////////////////////////////////////");
        byte b1 = 23, b2 = 35;
    Object o = b1^b2;
    System.out.println((o instanceof Integer) + " -- " + (o instanceof Byte));

    System.out.println("/////////////////////////////////////////////////");
    for(int i = 127; i < 129; i++) {
      Integer a = i, b = i, c = new Integer(i), d = (Integer)i;
      System.out.println((a == b) + " " + (b == c) + " " + (c == d) + " " + (d == a));
      //System.out.println(a.equals(b) + " " + b.equals(c) + " " + c.equals(d) + " " + d.equals(a));
    }

    System.out.println("/////////////////////////////////////////////////");    
    System.out.println(frack());
    }

    static int frack() {    
    double d1 = Math.atan(-0/1.), d2 = Math.atan(-0./1);    
    Double D1 = Math.atan(-0/1.), D2 = Math.atan(-0./1);  
    
    int c = 0, b = 0;
             
    while(d1 == d2) {    
      try {
        try {
          return D1.equals(D2) ? --b : ++c;
        } finally {
          return (double)D1 == (double)D2 ? ++c : --b;
        }
      } finally {
        if(D1.doubleValue() == D2.doubleValue())
          break;        
        else
          continue;
      }            
      }
    
    if(D1.isNaN() || D2.isNaN() || D1.isInfinite() || D2.isInfinite())
    {
      return --b;
    }
    
    if(D1 < D2 || D1 > D2 || D1 == D2)
    {
      return --b;
    }
    
    return D1 <= D2 ? ++c : --b;
  }

    public static void rotate1(int input[]) {
      final int N = input.length;
        int temp[] = new int[N];
        for (int i = 0; i < N; i++)
            temp[i] = input[(i + 1) % N];
        input = temp;
    }

    public static void rotate2(int input[]) {
      final int N = input.length;
        int temp = input[0];
        for (int i = 0; i < N-1; i++)
            input[i] = input[i + 1];
        input[N-1] = temp;
    }
}