6.170 Recitation

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6.170 Recitation

• Allen Miu

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Announcements

• Quiz 1 Review March 3, 730pm, 34-101
• Problem Set 3 March 4
• Quiz 1 (L1-L10) March 6 during class
• 54-100 for usernames a-j
• 34-101 for usernames k-z
• http//web.mit.edu/6.170/www/
• Section number TAs name on problem set
  submissions

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Problem 5 MDD
4
Object Models

• Describe relationships between sets of objects
• Sets (and subsets)
• Relationships
• Set and relationship constraints multiplicity
  and mutability

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Subtype Relationships
subtype (pure)
exhaustive
exclusive (disjoint)
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Multiplicity

• Uses field arrow
• M to N relationship m, n, , !, ?,

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Mutability

• Modifiability of fields
• At the src
• At the target
• Modifiability of sets
• Cardinality , , !, ?
• Migration dynamic, static, fixed

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MDD Example Sets
People
Men
Player
Nice Guy
Monk
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MDD Example Relationships
People
Women
Men

!
?
girlfriends
Player
Nice Guy
Monk
!
girlfriends
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MDD Example Blaspheme
People
Women
Men

!

?
girlfriends
Player
Nice Guy
Monk

!
girlfriends
girlfriends
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Problem 1 CardValue and CardSuit

1. Static members in CardSuit.
2. Separate CardSuit class.
3. CardSuit constructor if (this null)
4. CardValue CardSuit constructors private
5. CardValue.equals()
6. CardValue implement the Comparable interface

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Problem 2 Card

• public int compareTo(Object o)
• if (o null) throw new NullPointerException()
• if (!(o instanceOf Card)) throw new
  ClassCastException()
• Card c (Card)o
• int suitCompare getSuit().compareTo(c.getSuit()
  )
• if (suitCompare ! 0) return suitCompare
• return getValue().compareTo(c.getValue())

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Problem 2 Card

• public boolean equals(Object otherCardObject)
• if (!(otherCardObject instanceof Card))
• return false
• Card otherCard (Card)otherCardObject
• (1) return (value otherCard.value)
• (suit otherCard.suit)
• (2) return (this.compareTo(otherCard) 0)
• (3) return this.hashCode()
  otherCard.hashCode()

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Problem 3 Deck

• public Deck()
• cards new ArrayList(52)
• for (int i0 ilt4 i)
• for (int j0 jlt13 j)
• cards.add(new Card( (CardValue)(CardValue.VA
  LUES.get(j)),
• (CardSuit) (CardSuit.SUITS.get(i))))
• CardValue.VALUES.size() instead of 13
• CardSuit.SUITS.size() instead of 4

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Problem 3 Deck

• public void removeCard(Card c)
• cards.remove(c)
• public void removeCard(Card c)
• if ((c null) !cards.contains(c))
• return
• cards.remove(c)
• --------------------------------------------------
  -------------------------------------
• public void shuffle()
• Collections.shuffle(cards)

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Problem 4 TwoPair

• public static PokerRanking evaluateHand(Hand h)
• if (!validHand(h)) return null
• Iterator it h.listCardsAcesHigh()
• SortedSet pairs PokerRanking.findNOfAKinds(it,
  2)
• if (isValidHand(h) pairs.size() 2)
• Card pair1 (Card)pairs.first()
• Card pair2 (Card)pairs.last()
• removeNCardsWithValue(it, 2, pair1.getValue())
• removeNCardsWithValue(it, 2, pair2.getValue())
• SortedSet discard findNOfAKinds(it,
  1) return new TwoPair(pair1, pair2, discard)
• else
• return null

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Problem 4 TwoPair

• public static PokerRanking evaluateHand(Hand h)
• if (!isValidHand(h)) return null
• SortedSet pairsSet findNOfAKinds(h.listCards
  AcesHigh(), 2)
• if ((pairsSet.isEmpty()) (pairsSet.size()
  lt 2)) return null
• Card firstPair (Card) pairsSet.first()
• Card secondPair (Card) pairsSet.last()
• SortedSet discardableCards
  convertToSortedSet(h.listCardsAcesHigh())
• removeNCardsWithValue(discardableCards.iterato
  r(), 2, firstPair.getValue())
• removeNCardsWithValue(discardableCards.iterato
  r(), 2, secondPair.getValue())
• return TwoPair(firstPair, secondPair,
  discardableCards)

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instanceof v.s. getClass

• ClassB extends ClassA
• ClassA a new ClassA()
• ClassB b new ClassB()
• ClassA ab new ClassB()
• a instaneof ClassA
• b instanceof ClassA
• a.getClass().equals(b.getClass())
• ab instanceof ClassA ab instanceof ClassB