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public final class Card implements Comparable {
  private String suit;
  private int rank;

  public Card(String s, int r) {
    if (s == null)
      throw new NullPointerException();
    suit = s;
    rank = r;
  }

  public boolean equals(Object o) {
    if (o instanceof Card){
      Card c = (Card)o;
      return suit.equals(c.suit) || (rank == c.rank); // bad
    }
    return false;
  }

//This method violates its contract
  public int compareTo(Object o){
    if (o instanceof Card){
      Card c = (Card)o;
      if(suit.equals(c.suit)) 
        return 0;
      if((c.rank >= rank + Integer.MIN_VALUE) && (c.rank <= rank + Integer.MAX_VALUE)) // check for integer underflow/overflow
        return c.rank - rank;
    }
    throw new ClassCastException();
  }

  public static void main(String[] args) {
    Card a = new Card("Clubs", 2);
    Card b = new Card("Clubs", 10);
    Card c = new Card("Hearts", 7);
    System.out.println(a.compareTo(b)); //returns 0
    System.out.println(a.compareTo(c)); //returns a negative number
    System.out.println(b.compareTo(c)); //returns a positive number
  }
}