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 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()

Manba:

G’ayratjon Rayimjonov