ArrayList

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ArrayList
2
????? array ????????????

• ??? index ?????????????????????????????
• ????????????????????????????????
• ????????????????????????????????????????
• ?????????????????? List Interface
  ?????????????????????????
• clone
• ensureCapacity
• trimToSize
• ????????? Object ????????

3
?????????????

• public ArrayList(int initialCapacity)
• Throw IllegalArgumantException ???
  initialCapacity lt0
• ArrayListltStringgtname new ArrayListltStringgt(100)
  
• ???????????????? ???????????????????????????? 10
  ??????

4
???????????????????

• public ArrayList(Collectionlt? Extends Egt c)
• ????????? c ??????????????????????????????????????
  
• ???????????????????????????????????? c
• ????????????????????????????? 110 ??? c
• Worst time O(n)
• ???????????????? c ???????????????????????????????
  ???? ????????????????????????
• ???????? womanList ??????????????? Woman
  ?????????????????? People
• ?????????????? ???????????????? People ??????
  womanList
• ArrayListltPeoplegt a new ArrayListltPeoplegt(womanL
  ist)

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• ????????????????????????????????????????? c
  ???????? ????????????? shallow copy ????????
• ????????????????? clone()
• ArrayListltPeoplegt a (ArrayListltPeoplegt)womanList
  .clone()
• Shallow copy ?? reference ????????????????????
  ?????????????????????? ???????????????????????????
  ????????????????????????????
• ???????????????????? a womanList
  ???????????????? a ???????? womanList ???

6
Shallow copy
womanList
w1
w3
w2
a
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Shallow copy (2)

• ?????????????? ??????????????
• womanList.add(new People(MRS.X)) ???
• a.add(new People(MR.A.J.)) ?????

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• new ArrayListltPeoplegt(womanList) ???
• (ArrayListltPeoplegt)womanList.clone()
• ????????????????????
• ?????????????????????????????????????
• ????????? copy constructor ???????????????? 110
  ???????????????

9
????????????????????????????

• System.arraycopy(array1, i, array2, i2, 3)
• ?????????? array1 ??? index i
• ????? array2 ??????????? index i2
• ????????? 3 ???

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public boolean add(E element)

• ??????????????????????????
• Worst time O(n), Avg time constant
• ???????? true ?????????????????????? (????????
  true ????)

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public E get(int index)

• ?????????????? ? ?????????????
• Throw indexOutOfBoundsException ???
  size()ltindex, ???? indexlt0

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public E set(int index, E element)

• ?????????????????? index ???? element
• ???????????????????????????? index ???
• Throw indexOutOfBoundsException ??? size()ltindex
  ???? indexlt0
• Worst time constant

13
public void add(int index, E element)

• ???? element ?????? ? ??????? index
• ????????????????????????????????
• Worst time O(n)
• Throw indexOutOfBoundsException ??? size()lt index
  ???? indexlt0

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public E remove(int index)

• ????????? ? ??????? index ?????
• ???????????????????????????????
• ??????????????????????????
• Throw indexOutOfBoundsException ??? size()ltindex
  ???? indexlt0

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public int indexOf(Object element)

• ????????????????? element ?????????????????????
• ???????? ?????????????????????????????? ???? -1
  ???????????
• ????????????????????????????????? equals()
• Worst time O(n)

16
ArrayList class heading

• public class ArrayListltEgt extends
  AbstractListltEgt implements ListltEgt, RandomAccess,
  Cloneable, java.io.Serializable
• ???????
• private transient E elementData
• Transient ?????????????????????????????
  serialization ??????????????
• private int size

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??????????????????????????????

• public ArrayList (int initialCapacity)
•  
• elementData new Object initialCapacity
•  
• public ArrayList ( )
•  
• this (10)
•  

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• public ArrayList(Collectionlt? extends Egt c)
•  
• this((c.size()110)/100) // ?????? 10
• Iterator i c.iterator( )
• while (i.hasNext( ))
• elementDatasize i.next()
•  

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????????????????? ????? add(E element)

• public boolean add(E element)
• ensureCapacity(size1) //?????????????????????
• elementDatasize element
• return true

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public void ensureCapacity(int min)

• modcount //???????????
• int oldCapacity elementData.length
• if(mingtoldCapacity) //??????????????????????
• E oldData elementData
• int newCapacity (oldCapacity3)/21
  //??????? 50
• if(newCapacity lt minCapacity) //???????????????
• newCapacity min // ???????????????????????
• elementData (E) new ObjectnewCapacity
• System.arrayCopy(oldData,0,elementData,0,size)

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modCount

• ????????????? ArrayList, LinkedList, TreeMap,
  TreeSet, HashMap, HashSet
• ??? ArrayList ???? inherit ????? AbstractList
• ??????????????????????????????? ???????? insert
  ???? remove ??? ArrayList ???
• ???????????????????????? expectedModCount ???????
• ??????????????????????????????????????????????????
  ?????? ???? itr.remove()
• modCount ???????????????
• ???????????????????????????????
  ??????????????????????????????????????????????????
  ?????????????????????????????????????????????????
  ??????????????????????
• ????????????????????????????????????
  ???????????????
• if (modCount!expectedModCount)
• throw new ConcurrentModificationException()

Fail fast
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modCount expectedModCount (???)
??????????????????????????????????

• public ModCountDriver( )
• ArrayList list new ArrayList( )
• list.add (yes)
• Iterator itr list. iterator( )
• list.add (good)
• itr.next( ) // exception thrown at this point

?????????????????
modCount, ??? expectedModCount ????????
next ???????????????
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??????? ensureCapacity

• Worst time ?????????????????? O(n)
• Avg time
• ????????? add ?? n/3 ????????? ???????????????????
  ??????
• ?????? ????????? add ?? (n/3)1 ?????
  ??????????????????? n ??????
• ??????????????? ??????????? add
  ??????????????????????? n/((n/3)1)
• ?????? 3 ?????
• Avg time constant

24
????????????????

• public Object clone()
• try
•  
• ArrayList v (ArrayList)super.clone()
  // copies size
• v.elementData new Objectsize
  
• System.arraycopy(elementData, 0,
  v.elementData,
• 0, size)
  
• v.modCount 0
• return v
• catch (CloneNotSupportedException e)
  
• // this shouldn't happen, since we are
  Cloneable
• throw new InternalError()

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????????????????? ????????????????????????????????

• ????? ArrayList ?????? n ??????
• ??? n ????? ????????????????? Double (i) ??? i
  ???????? 0 ?????????????
• ??? new Double (7.8) ??? index n/2
• ??????????????????? 2n / 3 ??????
• ??? 2.5 ???????????????????????????
• ????????????????????????????????

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1. public void processInput (String s)
2. int n Integer.parseInt (s)
3. ArrayList myList new ArrayList (n)
4. for (int i 0 i lt n i)
5. myList.add (new Double (i))
6. myList.add (n / 2, new Double (7.8))
7. myList.remove (2 n / 3)
8. double d ((Double)myList.get (n /
   2)).doubleValue( )
9. 2.5
10. myList.set (n / 2, new Double (d))
11. gui.println (myList) 

1
2
3
4
5
6
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????????? ArrayList VeryLongInt???????????
VeryLongInt

• protected ArrayListltIntegergt digits
• ???????????????????????????????????

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????????? ArrayList VeryLongInt class

• public VeryLongInt(String s)
• ????? VeryLongInt ????????? String
• Throw NullPointerException ??? s null
• VeryLongInt a new VeryLongInt(5629?3)
• ???????? 56293 ????????? a
• Worst time O(string length)

???????????????????
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??????? VeryLongInt(String s)

• ???????????????????????????
• ???????????????????????? ????????? 0
  ??????????????????????????
• ????????????????????????????

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• public VeryLongInt(String s)
• final char LOWEST_DIGIT_CHAR 0
• digits new ArrayListltIntegergt(s.length())
• char c
• int digit
• for(int i 0 ilts.length() i)
• c s.charAt(i)
• if(Character.isDigit(c))
• digit c - LOWEST_DIGIT_CHAR
• digits.add(digit) // auto convert

Avg time worst time O(n)
Avg time constant, Worst time constant
????????????????????????
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• public String toString()
• Return String ?????? VeryLongInt object ???
• 56293 ?????????? 5,6,2,9,3
• Worst time O(????????????)
• public String toString()
• return digits.toString()//??????????????????????
  ???????

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• public void add(VeryLongInt otherVeryLong)
• ?????? VeryLongInt
• Worst time O(???????????????????????????????????
  ??????)
• Throw NullPointerException ??? otherVeryLong
  null

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??????? add(VeryLongInt otherVeryLong)

• ??????????? ????????????????? (????????????????)
  ??????????????????????????????????????????????????
  ?????? sumDigits
• ???????? 135 ??? 79 ???????????? sumDigits ????
  412 ??????????????????????????? sumDigits
  ???????? ????????????????????????????????
  sumDigits
• ????? 214 ???????????????????

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• public void add(VeryLongInt otherVeryLong)
• final int BASE 10
• int largerSize, partialSum, carry 0
• ArrayListltIntegergtsumDigits new
  ArrayListltIntegergt()
• if(digits.size()gtotherVeryLong.digits.size())
• largerSize digits.size()
• else
• largerSize otherVeryLong.digits.size()
• for(int i0 iltlargerSize i)
• partialSum least(i) otherVeryLong.least(i)
  carry
• carry partialSum / BASE
• sumDigits.add(partialSum BASE)
• if(carry1)
• sumDigits.add(carry) //????????????????? carry
  ???????????
• Collections.reverse(sumDigits)
• digits sumDigits

??????? i ?????????????????
O(n)
Constant time
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• protected int least(int i)
• if(igtdigits.size())
• return 0
• return digits.get(digits.size()-i-1)

Constant time