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26-dars - Javada Stringlar.

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, Iterable<?
extends 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 <strong>String isEmpty()</strong>

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()

Manba:


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Rayimjonov G'ayratjon


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