Algoritmlash asoslari

Saralashdan oldin:

0: R

4: Z

5: A

66: Q

9: P

77: Y

11: C

Saralashdan keyin:

0: R

4: Z

5: A

9: P

11: C

66: Q

77: Y
HashMap ni Comerator dan foydalanib, value(qiymat)ini saralashga misol:
import java.util.Collections;

import java.util.Comparator;

import java.util.HashMap;

import java.util.Iterator;

import java.util.LinkedHashMap;

import java.util.LinkedList;

import java.util.List;

import java.util.Map;

import java.util.Set;

public class HMapSortingByvalues {

public static void main(String[] args) {

HashMapString> hmap = new HashMapString>();

hmap.put(5, "A");

hmap.put(11, "C");

hmap.put(4, "Z");

hmap.put(77, "Y");

hmap.put(9, "P");

hmap.put(66, "Q");

hmap.put(0, "R");

System.out.println("Saralashdan oldin:");

Set set = hmap.entrySet();

Iterator iterator = set.iterator();

while(iterator.hasNext()) {

Map.Entry me = (Map.Entry)iterator.next();

System.out.print(me.getKey() + ": ");

System.out.println(me.getValue());

}

MapString> map = sortByValues(hmap);

System.out.println("Saralashdan keyin:");

Set set2 = map.entrySet();

Iterator iterator2 = set2.iterator();

while(iterator2.hasNext()) {

Map.Entry me2 = (Map.Entry)iterator2.next();

System.out.print(me2.getKey() + ": ");

System.out.println(me2.getValue());

}

}

private static HashMap sortByValues(HashMap map) {

List list = new LinkedList(map.entrySet());

// Bu yerda custom komparator aniqlandi

Collections.sort(list, new Comparator() {

public int compare(Object o1, Object o2) {

return ((Comparable) ((Map.Entry) (o1)).getValue())

.compareTo(((Map.Entry) (o2)).getValue());

}

});

// Bu yerda men Hashmap'da tartiblangan ro'yhatni ko'chiryapman

// LinkedHashMap'dan foydalanib, kiritish tartibini saqlash uchun

HashMap sortedHashMap = new LinkedHashMap();

for (Iterator it = list.iterator(); it.hasNext();) {

Map.Entry entry = (Map.Entry) it.next();

sortedHashMap.put(entry.getKey(), entry.getValue());

}

return sortedHashMap;

}

}
ekranda:

Saralashdan oldin:

0: R

4: Z

5: A

66: Q

9: P

77: Y

11: C

Saralashdan keyin:

5: A

11: C

9: P

66: Q

0: R

77: Y

4: Z
TreeMap

TreeMap ham huddi TreeSetga o'xshab ma'lumotlarni saralaydi, farqi TreeMap keybo'yicha saralaydi.

TreeMap ham huddi HashMap'ga o'xshab Map'dan implement oladi. Farqi HashMap ma'lumotlarni saralab chiqarmaydi.


Key bo'yicha saralashga misol:

import java.util.TreeMap;

import java.util.Set;

import java.util.Iterator;

import java.util.Map;

public class Details {

public static void main(String args[]) {

/* Bu yerda TreeMap'ni qanday e'lon qilish */

TreeMapString> tmap =

new TreeMapString>();

/*Adding elements to TreeMap*/

tmap.put(1, "Data1");

tmap.put(23, "Data2");

tmap.put(70, "Data3");

tmap.put(4, "Data4");

tmap.put(2, "Data5");

/* Iterator'dan foydalangan holda kontentni ko'rsatish */

Set set = tmap.entrySet();

Iterator iterator = set.iterator();

while(iterator.hasNext()) {

Map.Entry mentry = (Map.Entry)iterator.next();

System.out.print("key is: "+ mentry.getKey() + " & Value is: ");

System.out.println(mentry.getValue());

}

}

}
ekranda:

key is: 1 & Value is: Data1

key is: 2 & Value is: Data5

key is: 4 & Value is: Data4

key is: 23 & Value is: Data2

key is: 70 & Value is: Data3

ko'rib turganingizdek ma'lumotlar key bo'yicha saralanib chiqarildi.

TreeMap'da ham elementlarni olish, qo'shish jarayonlari huddi HashMapga o'xshash bo'ladi.

27-dars. Javada Stringlar
JAVADA STRING

Javada String asosan char tipidagi qiymatlar  ketma-ketligini ifodalovchi ob’yekt hisoblanadi. Belgili massiv esa javadagi String kabi ishlaydi, ya`ni:

Source code

1. char[] ch={'j','a','v','a','t','p','o','i','n','t'};

2. String s=new String(ch);

Kodimiz

Source code

1. String s="javatpoint";

Kabi ishlaydi.

Java String klasi string ustida compare(), concat(), equals(), split(), length(), replace(), compareTo(), intern(), substring() kabi bir necha funksiyalarni ishlatib bir qator amallarni bajarish imkonini beradi.

java.lang.String klasi Serializable, Comparable va CharSequence interfeyslarini implement qiladi.



CharSequence interfeysi belgilar ketma-ketligini ifodalashda ishlatiladi. U String, StringBuffer va StringBuilder klaslari tomonidan implement qilinadi. Bundan kelib chiqadiki, biz Javada stringni shu uch klasdan istalgani bilan yasay olamiz.



String doimiydir, ya’ni uni o`zgartirib bo`lmaydi. Qachonki biz stringga o’zgartirish kiritsak, yangi instance variable – doimiy qiymat hosil qilinadi. O`zgaruvchan string uchun StringBuffer va StringBuilder klaslaridan foydalanish mumkin.

Biz o`zgarmas(immutable) stringlarga keyinroq to`xtalamiz. Avval biz javadagi string haqida to`liq ma’lumot olamiz.

№	Funksiyalar	Ta`rifi
1	char charArt(int index)	ma’lum bir index uchun char qiymat qaytaradi
2	int length()	Stringni uzuligini qaytaradi
3	static String format(String format, Object … args)	String format qaytaradi
4	static String format(Locale I, String format, Object …args)	Berilgan local string format qaytaradi
5	String substring(int beginIndex)	boshlang’ich index uchun
6	String substring(int beginIndex, int endIndex)	Boshlang’ich va oxirgi index uchun
7	boolean contains(CharSequence s)	Ketma ket kelgan char larnig true yoki false qiymatlarini qaytaradi
8	static String join(CharSequence delimiter, CharSequence …elements)	Stringlarni qo’shadi
9	static String join(CharSequence delimiter, Iterableextends CharSequence> elements)	Stringlarni qo’shadi
10	boolean  equals(Object another)	String va ob’yektlarini tekshiradi
11	boolean isEmpty()	Stringni bo’sh ekanini tekshiradi
12	String concat(String str)	Muayyan stringlarni birlashtiradi
13	String replace(char old, char new)	Belgilangan char larni almashtiradi
14	String replace(CharSequence old, CharSequence new)	Ketma ket kelgan char’lari almashtiradi
15	String trim()	Bo’sh joyni tushirib qoldiradi
16	String split(String regex)	Stringlarni teng bo’ladi
17	String split(String regex, int limit)	Stringlarni limit bilan bo’ladi
18	String intern()	String ni biror bir qiymatda ushlab turadi
19	int indexOf(int ch)	Charlarni aniq index ‘ini qaytaradi
20	int indexOf(int ch, int fromIndex)	Charning boshlanish qiymati bilan aniq index qaytaradi
21	int indexOf(String substring)	Stringni qaysi index da turganini qaytaradi
22	int indexOf(String substring, int fromIndex)	Substring ko’rsatkichidan index o’rnini
23	String toLowerCase()	Harflarni kichigi bilan almashtiradi
24	String toLowerCase(Locale l)	Local berilgan harflarni kichigiga almashtiradi
25	String toUpperCase()	Berilgan harflarni kattasiga almashtiradi
26	String toUpperCase(Locale l)	Local berilgan harflarni kattasiga almashtiradi

Funksiyalarga misollar