O Type of array element

Transcription

1 ! " #! $ % % # & : ; a ontiguous sequene of variables. all of the sae type. Eah variable is identified by its index. Index values are integers. Index of first entry is. ' ( ) * + May /,. - ( & ( ( J K K M N ` a a b d O Type of array eleent P priitive type (har, int, boolean, double, et.) Q or Q referene type (, PlayingCard, Objet, et.) R ength of array: nuber of oponent variables R If length of array is n, index range fro to n-. R length of array is fixed after reation. R Aess of an array variable is in onstant tie R They are sublass of Objet R Have a publi final int oponent length. R int[] denotes the lass array-of-int, R [] denotes the lass array-of-. May >?@A BCDEFG HI = May S f g h i j i j k b a a b d f g h i j i j k b a a b d R int[] grades; Creates an array-of-int naed grades [] s; R Creates an array-of- naed s. R Note: delaring the variable does not reate an array. grades = new int[]; s = new []; R reate two arrays of, and R assign referenes to speified variables int[ ] [ ] May grades s e grades May s l

2 ! " # $ % " & & " ' ( " & " ) #* + grades[] Index is an int variable We an write:, Can assign eah oponent of array grades via: for (int i = ; i grades.length; i = i+) grades[i] = ; grades[] = ; grades[] = grades[]/; Siilarly, we an write: s[] = new ( ); s[].payfees(); Iportant: index value used to aess an array variable ust be in range to length of array - May May : & & " ' ; * = >! A > ; + B C * D! A : " & & " ' Z ) " + * ; # +! [ D #* [ *! "! A, Use of an index that is either negative or greater than or equal to the array length results in a run-tie error ArrayIndexOutOfBoundsExeption. for (int i = ; i = grades.length; i = i+) grades[i] = ;, Alloate array to hold referenes to of list., Array oponent referenes first eleent of list, oponent referenes the seond, and so on., ength of list is bounded by length of array, and array length is fixed when the array is reated., Call list ipleentation lass BoundedistEleent>, Requires that a axiu list size be speified when, Stores value in all oponents of array grades, but fails on last iteration when i equals grades.length with error E F F G H I J K M N O P N Q R S O J K T U M V W P XS J May. / - an instane is reated. May. / Y R S O J K K ^ XT P _ U ` a J P b G J K ^ XT P _ U ` a J P b r s t u v w v x yz { s u z { t { s, isteleent> interfae does not put a requireent on the size of lists, BoundedistEleent> ust plae a requireent in its add ethods: list size be less than its axiu. d Preonditions for Boundedist add are stronger than the preonditions for ist add. Thus Boundedist should not be a subtype of ist. d Ipleent Boundedist as an independent lass, while having the sae ethods as ist. May. / \] publi lass BoundedistEleent> A list of Eleents with a fixed axiu size. publi Boundedist (int axsize) Create a new Boundedist with a speified axiu size. require: axsize >= ensure: isepty(new Boundedist(n)) Ensure guarantees it reates an epty list. The ipleentation will define an array with axsize as the size of the array. Calling the array oponent : May.length == axsize f ghi jklno pq ee

3 data oponents array ontaining the, an int variable ontaining the list length. We annot define: private Eleent[] ; It s not legal to define an array using type paraeter Eleent to speify the type of the array. For arrays we ust use Objet as the type of its. May Boundedist private Objet[] ; // of the list private int size; // size of the list size // [] through [size-] are valid; // [size] through [.length-] // are not.!. / / : : ; / publi Boundedist (int axsize) { assert axsize >= ; = new Objet[axSize]; size = ; Exaple of use: Boundedist> roll = new Boundedist>(); Objet[ ] May " #$%&'()*+,- = > B C D E FG H G A B G FH J FG H G A B = A add(int,eleent) shuffles portion of the array down. Exaple: list ontains six, and a new eleent is to be inserted at index position, entries at indies :,,, ust be oved down, starting with the last, to ake roo for new eleent. [ \ ] ^ _ \ ` ab ab d \ e f a] g h\ ] \ b i a^ b reove(int) shuffles portion of the array up. Exaple: list ontains six, and ust reove eleent at index position entries at indies :,,, ust be oved up, starting with the the one at index. MN May " #$%&'()*+,- May O PQRSTUVWX YZ j kl n o p u s qr qp t j kl n o p s qp qr t ˆ ˆ Š Œ Ž Ž publi Eleent get (int index) { assert = index && index size; return (Eleent)[index]; publi int indexof (Eleent eleent) { int i = ; while (i size &&!eleent.equals([i]) i = i+; if (i size) return i; else return -; May x yz{ ~ ƒ vw ˆ ˆ Š Œ Ž Ž publi void add (Eleent eleent) { assert size.length; [size] = eleent; size = size+; publi void add (int index, Eleent eleent) { assert = index && index = size; assert size.length; for (int i = size-; i >= index; i = i-) [i+] = [i]; [index] = eleent; size = size+; May x yz{ ~ ƒ v

4 May publi void set (int index, Eleent eleent) { assert = index && index size; [index] = eleent; publi void reove (int index) { assert = index && index size; for (int i = index; i size-; i = i+) [i] = [i+]; size = size-; For objets with lists as oponents values, provide a query that returns a opy of the list oponent rather than the list itself. shallow opy : list is opied, but not its. publi BoundedistEleent> opy () { BoundedistEleent> thecopy = new BoundedistEleent>(this..length); thecopy.size = this.size; for (int i = ; i this.size; i = i+) thecopy.[i] = this.[i]; return thecopy; May " # $ % & &' ( ) ' * + ', % & -#. /,. - # % ) ' * - " * ) ' * + ', % & -#. / ) ' C * '. # % ) ' * - Boundedist this size Objet [ ] length size Objet [ ] a b Boundedist thecopy size May Objet [ ]! May Boundedist thecopy size Objet [ ] : ;=>?@ AB acopy bcopy Copy D EF G H I H J K F M The lass Objet defines a ethod lone speified as proteted Objet lone () throws CloneNotSupportedExeption Create a opy of this Objet. N throws CloneNotSupportedExeption eans ethod ay fail during exeution N Objet s lone produes a very shallow opy of the Objet: all instane variable values are opied. ] ^ _` a b d e f bg h ^ a i ^ ^ d ` d h j ^ k a ` d l ba e k _ d ^ If obj is an objet : obj!= obj.lone() obj.equals(obj.lone()) obj instaneof soetype if and only if obj.lone() instaneof soetype Sine lone returns an Objet, you ust ast result: Boundedist this size Objet[ ] Date date = new Date( ); Date date = (Date)date.lone(); Boundedist thecopy May size : ;=>?@ AB May Q RST UVWXYZ [\ OP

5 * +, -. /. + publi interfae Cloneable { ; It s an interfae with no ethods. Ipleented by any lass that supports (or overrides) lone. lone heks to see if objet is an instane of a lass ipleenting Cloneable. If so, akes shallow opy of objet. Otherwise, fails with CloneNotSupportedExeption. We hoose not to define Boundedist to ipleent Cloneable If we do, lone() fores us to define equals() in Boundedist. Boundedist is a utable lass, with no iutable set of properties to define equals() We provide our own opy algorith. May May! "#$%&' () : ; = A = : B CD C> > CE = E F G G H CD I B@ = > > CE = A J ist an be aessed effiiently: get(int), add(eleent), and set(int,eleent) exeute in onstant tie. K operations reove(int),add(int,eleent), indexof(eleent) are linear: Nuber of steps required inreases in proportion to size of list. On average, half the list ust be shifted up or down to add or reove. M lient ust have a good idea of the ultiate size of a list Choosing a size that is too large will waste spae; hoosing a size too sall will ause the progra to fail. May! "#$%&' () \ ] ^ ] _ ` a b d e ` e _ f g h i j j ] ` e k l no p n q r s t q u v p w x yz {p n s tq u v w v ~ p u n q r {v r o ƒ r ~ {p ƒ r q ƒ ~q q s t q u v {p q q u v q ˆ u n r v r Šq {v q s tq u v p ƒ q v ~ r p Œ k x ~ q o n q n n ƒ q v q { q { {v p q v o v o q Œ k l p r v ~ q r s tq u v p {v ~ n p v r v v p Ž q v o v o q q u n n v {r n {v p q v o v o q { p v n v {n v {r Œ k l n no v o q {p l yz ~q q l u n s q n š œ u n p p r u n p p Œ k ž v q q ƒ q v p ƒ p v u r ƒ q n n o p Ÿ r ƒ u n p pq p Œ k x ~ q q v ~ r Ÿ n n n o {p r v n v r Ÿ {v p v o q Œ k r r v r Ÿ s r q r p Œ k q v ~ {p {Š q n v { p v n v {n v {r n {p n {Ÿq v {ƒ q u r p v n v Œ x ~ p n no p n q q n o r o pq ƒ { o n ƒ {u o r u n no p { q q p u { v {r r u q n v {r r o n u n v { u q ƒ q v r q u q ƒ q v {v p p { q n v v {ƒ q Œ k l v u n n v {r u n { {v {n { q n no Š n {n s q {v ~ v ~ q n n o q q p p {r s v u n r v pq v ~ n v q q p p {r v r ƒ n v u ~ n n ƒ q v q p Œ May P QRS TUVWXY Z[ NO \ ] ^ ] _ ` a b d e ` e _ f g h i j j ] ` e k l no p {ƒ q ƒ q v { v q Ÿ n u q p µ r q n s q q {n { n s q Œ µ n r v r Š q {v q v ~ q ƒ Œ k {Š q Date [] days = new Date[]; Date [] twindays = days.lone(); days.equals(twindays) ¹º»¼ ½ ¾»½º À Á  ¹Ã º Ä T[] table; Å º Æ Ä Ç Ä» ½ ½ ¹È ĺ ¼ ¹Ä ½ É Ä Æ º ½ Ç ¾ Æ» ½ ½º ½ Ê Ç Ç É º ¼ É Ë É Ç º Æ Ì Ç ¾ ¹É ½ º ÄÉ Ê ¹º ½ À Í Ç Î ¹É ¹½ ½ É É ¹Æ»» Æ Ì º Æ Ï º ¼ À Á Ð ¾ Ë Ñ ½ Ò Ó Æ» ½ ½ Ç ¾ Ë Î ¹Ä ½ É ÄÆ º ½ Ç ¾ Ë ÑÔÕ Æ Ä Ó º Ò ½º ¼ ¾ Ç Ê ¹Ä ½ É ÄÆ º ½ Ç ¾ Ë ÔÕÎ ¹Àº À Ë Ñ ÔÕ ¹½ ½ Ò Ó Æ» ½ ½ Ç ¾ Ë ÔÕÖÖÖ Ø ÙÚ Ú Û Û Ü Ú Ý Þ ß à Û á â ã ä å À Integer ¹½ ½ Ò Ó Æ» ½ ½ Ç ¾ ObjetÎ Ó ÒÉ Integer[] ½ ÌÇ Ò»¼ Ä Ç É Ó º ½ Ò Ó Æ» ½ ½ Ç ¾ Objet[]. æ Á ç ÒÉ è à é Ê Ç Ã ¹¼ º ½ ArrayStoreExeption ê È ¹Ã º Ä void pro (Objet[] objs){objs[] = new Objet(); Á Æ Ä ë É Æ Ì Objet[] Å ¹É Ì Integer[], Ó ÒÉ É Ì º Ä É Ì º ¼ Ä ë ¹Æ É é º Ç ¾ objs ¹½ Integer[], ½ Ç É Ìº ½ ½ ¹È Ä ë º ÄÉ Å ¹»» Ê ¹½ º É Ì º º ì Æ º éé ¹Ç Ä À Ë Ìº é Ê Ç Ó»º ë ¹½ É Ì É é º Ê ¾º Æ É»»º È» Æ Ç ¼ º Î ë é Ê Ç ¼ Ò Æ º Ê Ò Ä íé ¹ë º º Ê ÊÇ Ê ½ ÖÖÖÖÖ æ Á  ¹Ã º Ä Î T[] table; table instaneof T[] == true Á Í ¹Ä Æ º ¹É Æ Ä Ä Ç É Ç Ã º Ê»Ç ¼ î Ó è º Æ É ï½ ë º É Ì Ç ¼ ½ Î É Ì Ò ½ Array Á Æ» ½ ½ æ Array Æ» ½ ½ ¾ Ç Ê Ò ½º ¾ Ò» ë º É Ì Ç ¼ ½ ¾ Ç Ê ÊÊ ½ Î Ó ÒÉ É Ì º ʺ ½ É É ¹Æ À May ª«±² ³