1-dars Java nima? Java dasturlash tili va platforma

while(iterator2.hasNext()) {

Map.Entry mentry2 = (Map.Entry)iterator2.next();

System.out.print("Key is: "+mentry2.getKey() + " & Value is: ");

System.out.println(mentry2.getValue());

}

}

}

ekranda:

key is: 49 & Value is: Fayzullo

key is: 2 & Value is: Zafar

key is: 3 & Value is: Jamshid

key is: 7 & Value is: Jalol

key is: 12 & Value is: Aziz

Map key and values after removal:

Key is: 49 & Value is: Fayzullo

Key is: 2 & Value is: Zafar

Key is: 7 & Value is: Jalol

Key is: 12 & Value is: Aziz

HashMap'ni elementlarni olishining ikki xil usuli bor

1. 
   For loop orqali
   
2. 
   While loop + iterator
   

misol:

import java.util.HashMap;

import java.util.Map;

import java.util.Iterator;

public class Details

{

public static void main(String [] args)

{

HashMapString> hmap = new HashMapString>();

// HashMap'ga elementlarni qo'shish

hmap.put(11, "AB");

hmap.put(2, "CD");

hmap.put(33, "EF");

hmap.put(9, "GH");

hmap.put(3, "IJ");

// FOR sikli

System.out.println("For Loop:");

for (Map.Entry me : hmap.entrySet()) {

System.out.println("Key: "+me.getKey() + " & Value: " + me.getValue());

}

//WHILE sikli & ITERATOR

System.out.println("While Loop:");

Iterator iterator = hmap.entrySet().iterator();

while (iterator.hasNext()) {

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

System.out.println("Key: "+me2.getKey() + " & Value: " + me2.getValue());

}

}

}

ekranda:

For sikli:

Key: 2 & Value: CD

Key: 3 & Value: IJ

Key: 33 & Value: EF

Key: 9 & Value: GH

Key: 11 & Value: AB

While sikli:

Key: 2 & Value: CD

Key: 3 & Value: IJ

Key: 33 & Value: EF

Key: 9 & Value: GH

Key: 11 & Value: AB

HashMap'ni key orqali saralash

Bu misolda HashMap'ning key'ini TreeMap'dan foydalanib saralash usulini ko'ramiz.

import java.util.HashMap;

import java.util.Map;

import java.util.TreeMap;

import java.util.Set;

import java.util.Iterator;

public class Details {

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 = new TreeMapString>(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());

}

}

}

ekranda:

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 key bo'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.

26-dars - Javada Stringlar.



JAVADA STRING

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

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

String s=new String(ch);

Kodimiz

String s="javatpoint";

Kabi ishlaydi.

Java String klassi 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 klassi Serializable, Comparable va CharSequence interfeyslarini implement qiladi.

CharSequence interfeysi belgilar ketma-ketligini ifodalashda ishlatiladi. U String, StringBuffer va StringBuilder klasslari tomonidan implement qilinadi. Bundan kelib chiqadiki, biz Javada stringni shu uch klassdan 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 klasslaridan foydalanish mumkin.

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

No	Funksiyalar	Ta`rifi
1	char charArt(int index)	ma'lum bir indeks uchun char qiymat qaytaradi
2	int length()	Stringni uzunligini 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 indeks uchun
6	String substring(int beginIndex, int endIndex)	Boshlang'ich va oxirgi indeks 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 obyektlarini 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 indeksini qaytaradi
20	int indexOf(int ch, int fromIndex)	Charning boshlanish qiymati bilan aniq indeks qaytaradi
21	int indexOf(String substring)	Stringni qaysi indeks da turganini qaytaradi
22	int indexOf(String substring, int fromIndex)	Substring ko'rsatkichidan indeks 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

Java String contains()

class ContainsExample{

public static void main(String args[]){

String name="what do you know about me";

System.out.println(name.contains("do you know"));

System.out.println(name.contains("about"));

System.out.println(name.contains("hello"));

}

}

Java String replace(CharSequence target, CharSequence replacement)

public class ReplaceExample2{

public static void main(String args[]){

String s1="my name is khan my name is java";

String replaceString=s1.replace("is","was");//replaces all occurrences of "is" to "was"

System.out.println(replaceString);

}

}

Java String equalsIgnoreCase()

public class EqualsIgnoreCaseExample{

public static void main(String args[]){

String s1="javatpoint";

String s2="javatpoint";

String s3="JAVATPOINT";

String s4="python";

System.out.println(s1.equalsIgnoreCase(s2));//true because content and case both are same

System.out.println(s1.equalsIgnoreCase(s3));//true because case is ignored

System.out.println(s1.equalsIgnoreCase(s4));//false because content is not same

}

}

Java String valueOf()

public class StringValueOfExample{

public static void main(String args[]){

int value=30;

String s1=String.valueOf(value);

System.out.println(s1+10);//concatenating string with 10

}

}

String charAt()

public class CharAtExample{

public static void main(String args[]){

String name="javatpoint";

char ch=name.charAt(4);//to'rtinchi elementini qaytaradi

System.out.println(ch);

}

}

Natija: t

String length()

public class LengthExample{

public static void main(String args[]){

String s1="javatpoint";

String s2="python";

System.out.println("string length is: "+s1.length());//javatpoint ning uzunligi 10 ga teng

System.out.println("string length is: "+s2.length());// python uzunligi 6 ga teng

}

}

Natija:
string length is: 10
string length is: 6

String format()

public class FormatExample{

public static void main(String args[]){

String name="sonoo";

String sf1=String.format("name is %s",name);

String sf2=String.format("value is %f",32.33434);

String sf3=String.format("value is %32.12f",32.33434);

System.out.println(sf1);

System.out.println(sf2);

System.out.println(sf3);

}}

Natija:
name is sonoo

value is 32.334340
value is 32.334340000000

String substring()

public class SubstringExample{

public static void main(String args[]){

String s1="javatpoint";

System.out.println(s1.substring(2,4));//va ni qaytaradi

System.out.println(s1.substring(2));// vatpoint ni qaytaradi

}}

Natija:
va

vatpoint

String join()

public class StringJoinExample{

public static void main(String args[]){

String joinString1=String.join("-","welcome","to","javatpoint");

System.out.println(joinString1);

}}

Natija:

welcome-to-javatpoint

String equals()

public class EqualsExample{

public static void main(String args[]){

String s1="javatpoint";

String s2="javatpoint";

String s3="JAVATPOINT";

String s4="python";

System.out.println(s1.equals(s2));//true

System.out.println(s1.equals(s3));//false

System.out.println(s1.equals(s4));//false

}}

Natija: true false false String isEmpty()

String isEmpty()

public class IsEmptyExample{

public static void main(String args[]){

String s1="";

String s2="javatpoint";

System.out.println(s1.isEmpty());

System.out.println(s2.isEmpty());

}}

Natija: true false

String concat()

public class ConcatExample{

public static void main(String args[]){

String s1="java string";

s1.concat("is immutable");

System.out.println(s1);

s1=s1.concat(" is immutable so assign it explicitly");

System.out.println(s1);

}}

Natija: java string java string is immutable so assign it explicitly

String replace(char old, char new)

public class ReplaceExample1{

public static void main(String args[]){

String s1="javatpoint is a very good website";

String replaceString=s1.replace('a','e');// hamma 'a' larni 'e' ga almashtirdi

System.out.println(replaceString);

}}

Natija: jevetpoint is e very good website

String trim()