Java Object Oriented Programming 09

Kiu d liu Collections

Bi 9 - Kiu d liu Collection

2

Ni dung

Kiu Collections

Giao din

Thc thi

Cc thut ton

Lp vt cha Set v Map


3

Kiu Collections

Mt collection, hay cn gi l container, l mt i tng dng nhm

nhiu phn t trong mt n v duy nht.

Cc collection c s dng lu tr, truy xut v thao tc d liu.

V d: mt tp hp cc qun bi, cc th mc th, mt danh b in

thoi,

http://docs.oracle.com/javase/7/docs/api/java/util/Collection.html


4

Collection framework

Mt collection framework l mt kin trc thng nht

biu din v thao tc vi cc d liu kiu collection.

Ba thnh phn ca mt collection framework:

Giao din: cc kiu d liu tru tng dng biu

din cc collection.

Thc thi: cc thc thi c th ca cc giao din ca collection.

Thut ton: Cc phng thc h tr nh sp xp, tm

kim, cc i tng thc thi cc giao din ca collection.


5

Java collection framework

Lm gim cng vic lp trnh,

Tng tc v cht lng chng trnh,

Cho php kh nng tng tc gia cc API khng lin quan,

Lm gim cng sc tm hiu v s dng cc API mi,

Lm gim vic thit k cc API mi,

Thc y ti s dng phn mm.


6

Ni dung

Kiu Collections

Giao din

Thc thi

Cc thut ton

Lp vt cha Set v Map


7

Giao din

Cc giao din li ca collection ng gi nhiu kiu khc nhau ca collection.

Cc giao din ny cho php cc collection c thao tc mt cch c lp

vi cc thc thi ca chng.

Collection

Set List

SortedSet

Queue

Map

SortedMap


8

Giao din

Tt c cc giao din ca Java collection framework l:

public interface Collection

Chng ta nn xc nh kiu E ca cc i tng cha trong collection.

E c th l mt trong cc kiu i tng:

Integer, Double, String

Object


9

Duyt collection

Hai cch duyt qua collection:

Bng cu trc foreach

Bng cc i tng Iterator

Cu trc foreach

for (Object o : collection)

do something

Cc i tng Iterator

Collection c;

Iterator iter = c.iterator();

while (iter.hasNext()) { E e = iter.next(); ...}


10

Ni dung

Kiu Collections

Giao din

Thc thi

Cc thut ton

Lp vt cha Set v Map


11

Thc thi

Cc thc thi thng dng ca collection

HashSet, TreeSet

ArrayList, LinkedList

PriorityQueue

HashMap, TreeMap

Bn nn c ti liu v cc lp ny trong API Documentation ny bit

y cc chc nng ca chng.

Packages: java.util.*


12

V d: List

// create a list of odd numbers

List odds = new ArrayList();

for (int i = 1; i < 50; i = i + 2) {

odds.add(i);

}

// print the list: first way

for (Integer i : odds) {

System.out.println(i);

}

// print the list: second way

Iterator iter = odds.iterator();

int i;

while (iter.hasNext()) {

i = iter.next();


}

// print the list: third way

for (int j = 0; j < odds.size(); j++) {

i = odds.get(j);


}


13

Ni dung

Kiu Collections

Giao din

Thc thi

Cc thut ton

Lp vt cha Set v Map


14

Cc thut ton

Cc thut ton a hnh trong Collection framework ca Java c

th ti s dng.

Tt c cc thut ton u c vit di dng phng thc

tnh.

i s u tin lun l Collection hot ng.

Nhiu thut ton lm vic trn danh sch.


15

Cc thut ton

Cc thut ton gm:

Sp xp

Xo trn

X l d liu thng xuyn

Tm kim

Hp nht

Vic tm kim cc gi tr cc i


16

Sp xp

Cc thut ton sp xp sp xp li danh sch cc phn t ca n tng dn theo mt quan h th t no .

Cc th t t nhin:

Xu k t

S

K t

Ngy thng

i tng ?


17

Sp xp

Giao din Comparable quy nh quan h th t cho mt lp.

Cc i tng ca mt lp c th c sp xp t ng nu

lp thc thi giao din Comparable.

Cc lp quan trng ca Java platform m thc thi giao din

Comparable bao gm:

Boolean, Byte, Character, Short, Integer, Long, Float, Double,

BigInteger, BigDouble.

String, Data, File, CollationKey


18

Sp xp

Nu ta c gng sp xp mt danh sch m cc phn t ca n

khng thc thi Comparable, phng thc sp xp s nm mt

i tng thuc lp ClassCastException.

Giao din Comparable:

public interface Comparable {

public int compareTo(T o);

}

Tr li mt gi tr ln hn, nh hn hay bng 0 ty thuc i tng ang xt ln hn, nh hn hay bng

vi i tng c so snh.


19

Sp xp

Example: Name.java, NameSort.java

public class NameSort { public static void main(String[] args) {

Name nameArray[] = {

new Name("John", "Smith"),

new Name("Karl", "Ng"),

new Name("Jeff", "Smith"),

new Name("Tom", "Rich")

};

List names = Arrays.asList(nameArray);

Collections.sort(names);

System.out.println(names);

}

}


20

Sp xp

Nu cc i tng m chng ta cn phi sp xp khng thc thi

Comparable, chng ta c th quy nh mt Comparator c dng

sp xp.

Giao din Comparator:

public interface Comparator {

int compare(T o1, T o2);

}


21

Sp xp

Gi s ta c mt lp Employee nh sau:

public class Employee implements

public Name name() { ...

public int number() { ...

public Date hireDate() { ...

...

}


22

Sp xp

ng nhin, chng ti c th sp xp danh sch cc nhn vin theo tn ca h.

Nu cn chng ta cng c th sp xp danh sch ny theo th

t v thm nin?


23

Sp xp

public class EmpSort {

static final Comparator SENIORITY_ORDER =

new Comparator() {

public int compare(Employee e1, Employee e2) {

int dateCmp = e2.hireDate().compareTo(e1.hireDate());

if (dateCmp != 0)

return dateCmp;

return (e1.number() < e2.number() ? -1 :

(e1.number() == e2.number() ? 0 : 1));

}

};

// Employee database

static final Collection employees = ... ;

public static void main(String[] args) {

List e = new ArrayList(employees);

Collections.sort(e, SENIORITY_ORDER);

System.out.println(e);

}

}

Ta so snh cc gi tr numbers khi m hai gi

tr ngy thng bng nhau


24

Xo trn

Thut ton xo trn l ngc li ca thut ton sp xp

Sp xp li mt danh sch da trn u vo t mt ngun ngu

nhin m tt c cc hon v c th xy ra vi kh nng ngang nhau.

Rt hu ch trong vic thc hin cc tr chi may ri (th, xc sc

...)


25

Xo trn

public class Shuffle {

public static void main(String[] args) {

List list = new ArrayList();

for (String a : args)

list.add(a);

Collections.shuffle(list, new Random());

System.out.println(list);

}

}

public class Shuffle {

public static void main(String[] args){

List list = Arrays.asList(args);

Collections.shuffle(list);

System.out.println(list);

}

}

Dng mt ngun ngu

nhin mc nh.


26

Thao tc d liu

Collection cung cp 5 thut ton thc hin cc thao tc d

liu trn cc i tng ca lp List:

reverse

fill

copy

swap

addAll


27

Tm kim

Thut ton binarySearch tm kim mt phn t trong

mt danh sch c sp xp.

Nu phn t c tm thy, ch s ca n c tr li, nu khng mt gi tr ch s m c tr li.

Hai dng ca thut ton:

Cho mt danh sch v mt phn t tm kim;

Cho mt danh sch, mt phn t tm kim v mt

Comparator.


28

Hp nht

Thut ton v tn sut:

m s ln xut hin ca mt phn t trong mt collection.

Thut ton xc nh tp ri nhau

Xc nh xem hai collection cc tch ri nhau khng.


29

Tm cc i

Gi tr cc i:

min ca mt collection

max ca mt collection

Hai dng:

Cho mt Collection

Cho mt Collection v mt Comparator

c cc ti liu JDK API xem cc thut ton v cc v d c th.


30

Example: Sort an Array

String[] fruits = new String[] {"Pineapple","Apple",

"Orange", "Banana"};

Arrays.sort(fruits);

int i=0;

for(String temp: fruits){

System.out.println("fruits " + ++i + " : " + temp);

}


31

Example: Sort an ArrayList

List fruits = new ArrayList();

fruits.add("Pineapple");

fruits.add("Apple");

fruits.add("Orange");

fruits.add("Banana");

Collections.sort(fruits);

int i=0;

for(String temp: fruits){

System.out.println("fruits " + ++i + " : " + temp);

}


32

Sort an Object with Comparable

public class Fruit{

private String fruitName;

private int quantity;

public Fruit(String fruitName, int quantity) {

this.fruitName = fruitName;

this.quantity = quantity;

}

public String getFruitName() {

return fruitName;

}

public void setFruitName(String fruitName) {

this.fruitName = fruitName;

}

public int getQuantity() {

return quantity;

}

public void setQuantity(int quantity) {

this.quantity = quantity;

}

} Bi 9 - Kiu d liu Collection

33


public class SortFruitObject{

static void showList(Fruit[] fruits){

int i=0;

for(Fruit temp: fruits){

System.out.println("fruits " + ++i + " : " + temp.getFruitName()

+ ", Quantity : " + temp.getQuantity());

}

}

public static void main(String args[]){

Fruit[] fruits = new Fruit[4];

Fruit pineappale = new Fruit("Pineapple",70);

Fruit apple = new Fruit("Apple",100);

Fruit orange = new Fruit("Orange",80);

fruits[0]=pineappale;

fruits[1]=apple;

fruits[2]=orange;


showList(fruits);

}

}

}

Fruit cannot be cast to

java.lang.Comparable


34


public class Fruit implements Comparable {








//override the compareTo() method

public int compareTo(Fruit compareFruit) {

int compareQuantity = ((Fruit) compareFruit).getQuantity();

return this.quantity - compareQuantity;

}

}


35

Sort an Object with Comparator

public class Fruit implements Comparable {








public int compareTo(Fruit compareFruit) {

public static Comparator FruitNameComparator

= new Comparator() {

public int compare(Fruit fruit1, Fruit fruit2) {

String fruitName1 = fruit1.getFruitName().toUpperCase();

String fruitName2 = fruit2.getFruitName().toUpperCase();

return fruitName1.compareTo(fruitName2);

}

};

} Bi 9 - Kiu d liu Collection

36

Sort an Object with Comparator

public class SortFruitObject{

static void showList(Fruit[] fruits){

int i=0;

for(Fruit temp: fruits){

System.out.println("fruits " + ++i + " : " + temp.getFruitName()

+ ", Quantity : " + temp.getQuantity());

}

}

public static void main(String args[]){

Fruit[] fruits = new Fruit[4];

Fruit pineappale = new Fruit("Pineapple",70);

Fruit apple = new Fruit("Apple",100);

Fruit orange = new Fruit("Orange",80);

fruits[0]=pineappale;

fruits[1]=apple;

fruits[2]=orange;


showList(fruits);

Arrays.sort(fruits, Fruit.FruitNameComparator);

showList(fruits;)

}

}

fruits 1 : Apple, Quantity : 100

fruits 2 : Orange, Quantity : 80

fruits 3 : Pineapple, Quantity : 70

fruits 1 : Pineapple, Quantity : 70

fruits 2 : Orange, Quantity : 80

fruits 3 : Apple, Quantity : 100


37

Ni dung

Kiu Collections

Giao din

Thc thi

Cc thut ton

Lp vt cha Set v Map


38

Tm cc ch trong vn bn

Cc ch (token, word) l mt dy k t lin nhau, ngn cch bi k t

trng.

V d:

Dng Tom likes Jerry gm 3 ch: Tom, likes, Jerry.

Dng Hc sinh hc sinh hc gm 5 ch:

C 3 ch khc nhau l Hc, sinh, hc.

Nu khng phn bit hoa thng th ch c 2 ch khc nhau.


39


Cho trc mt tp vn bn ting Anh hoc ting Vit, ta xt hai bi ton sau:

Lit k cc ch khc nhau trong vn bn

m tn s cc ch khc nhau trong vn bn


40


gii bi ton 1, ta dng kiu vt cha tp hp:

Giao din Set

Ci t ca Set l HashSet

gii bi ton 2, ta dng kiu vt cha nh x:

Giao din Map

Ci t ca Map l HashMap


41

Cc giao din trong th vin

Th vin cc lp vt cha c nhiu giao din cho php thao tc vi nhiu

kiu d liu thng dng:

Set, Map, List, Queue

Collection

Set List

SortedSet

Queue

Map

SortedMap


42

Reader reader = null;

BufferedReader bufferedReader = null; try { // open a reader using UTF-8 encoding so that we can

// read Vietnamese text reader = new InputStreamReader(new FileInputStream(fileName), "UTF-8"); bufferedReader = new BufferedReader(reader);

c tp vn bn

S dng bng m UTF-8

c tp


43

String line = null; // read the input file, line by line while ((line = bufferedReader.readLine()) != null) { // split the line into tokens String[] tokens = line.split(Constants.DELIMITERS); // add tokens to the set for (String token : tokens) { tokenSet.add(token);

}

}

public static final String DELIMITERS = "[\\s,\\.\\(\\)]+";

c tp vn bn

Biu thc chnh quy ch nh cc k t

trng, du phy, du chm, m ngoc,

ng ngoc


44

Nu thay HashSet bng TreeSet th ta c tp c sp xp theo th t t nhin ca phn t

Cc phn t l String s c sp theo th t t in

private Set tokenSet;

tokenSet = new HashSet();

public void print() {

System.out.println("There are " + tokenSet.size() + " different tokens."); for (String token : tokenSet) {

System.out.println(token);

}

}

S dng Set


45

Mi nh x c cp phn t: Key Value Trong bi ton 2, Key l token, Value l mt s nguyn m s ln token xut hin Key, Value u phi l cc kiu i tng (khng th l kiu d liu c s)

Key = String

Value = Integer

private Map tokenCounter;

tokenCounter = new HashMap();

S dng Map


46

// add tokens to the counter

for (String token : tokens) { Integer count = tokenCounter.get(token); if (count != null) { tokenCounter.put(token, count + 1); } else { tokenCounter.put(token, 1);

}

}

S dng phng thc get(Key) ly Value gn vi Key.

Nu khng c Key th hm get tr v null

Java 5+ t ng chuyn i gia i v new Integer(i) vi i l mt s nguyn

S dng Map


47

/**

* Prints the token counter to the standard console. */ public void print() { System.out.println("There are " + tokenCounter.keySet().size() + " different tokens."); for (String token : tokenCounter.keySet()) { System.out.println(token + " --> " + tokenCounter.get(token)); } }

Nu thay HashMap bng TreeMap th tp kha c sp xp theo th t t nhin.

S dng Map


Java Object Oriented Programming 09

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