10. Class va Object¶

Java — object-oriented programming, ya'ni obyektga yo‘naltirilgan dasturlash tili.

Shuning uchun Java'da class va object tushunchalari juda muhim.

Hozirgacha class haqida ozgina ko‘rgan edik. Endi uni yaxshiroq tushunamiz.

Class nima?¶

Class — obyekt uchun reja yoki qolip.

Masalan, biz Car nomli class yaratishimiz mumkin.

class Car {
    String rang;
    String model;
}

Bu yerda Car classi mashina haqida ma'lumot saqlashi mumkin.

Lekin Car hali haqiqiy mashina emas.

Uni qolip deb tasavvur qiling.

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Object nima?¶

Object — class asosida yaratilgan haqiqiy obyekt.

Masalan:

Car mashina1 = new Car();

Bu yerda mashina1 — Car classidan yaratilgan object.

Oddiy qilib:

Class  → qolip
Object → shu qolip asosida yaratilgan narsa

Masalan:

Car → mashina uchun qolip
mashina1 → bitta mashina
mashina2 → boshqa mashina

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Birinchi classimiz¶

Keling, Car classini yaratamiz.

class Car {
    String rang;
    String model;
}

Endi main() ichida object yaratamiz:

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

        Car mashina = new Car();

    }
}

Bu yerda:

new Car()

yangi Car object yaratadi.

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Objectga qiymat berish¶

Car classida ikkita ma'lumot bor:

String rang;
String model;

Object yaratgandan keyin ularga qiymat berishimiz mumkin.

Car mashina = new Car();

mashina.rang = "Qizil";
mashina.model = "BMW";

Endi object quyidagicha ma'lumotga ega:

rang  → Qizil
model → BMW

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Object ma'lumotlarini chiqarish¶

System.out.println(mashina.rang);
System.out.println(mashina.model);

Natija:

Qizil
BMW

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Bir nechta object¶

Bitta classdan bir nechta object yaratish mumkin.

Car mashina1 = new Car();
Car mashina2 = new Car();

Ularga turli qiymatlar beramiz:

mashina1.rang = "Qizil";
mashina1.model = "BMW";

mashina2.rang = "Oq";
mashina2.model = "Toyota";

Endi ikkita mustaqil object mavjud.

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To‘liq misol¶

class Car {
    String rang;
    String model;
}

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

        Car mashina1 = new Car();

        mashina1.rang = "Qizil";
        mashina1.model = "BMW";

        System.out.println(mashina1.rang);
        System.out.println(mashina1.model);
    }
}

Natija:

Qizil
BMW

---

Class ichida method¶

Class faqat ma'lumot saqlab qolmaydi.

Uning ichida methodlar ham bo‘lishi mumkin.

Masalan:

class Car {

    String rang;
    String model;

    void signalBer() {
        System.out.println("Bip-bip!");
    }
}

Object orqali methodni chaqiramiz:

Car mashina = new Car();

mashina.signalBer();

Natija:

Bip-bip!

---

Objectning o‘z methodi¶

Masalan:

class Car {

    String model;

    void yur() {
        System.out.println(model + " yurmoqda.");
    }
}

Keyin:

Car mashina = new Car();

mashina.model = "BMW";

mashina.yur();

Natija:

BMW yurmoqda.

Method objectning ma'lumotlaridan foydalanishi mumkin.

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Real hayotdagi misol¶

Classni uy loyihasiga o‘xshatish mumkin.

Masalan:

class Uy

Bu uy qanday bo‘lishini belgilaydi.

Keyin:

Uy uy1 = new Uy();
Uy uy2 = new Uy();

deb ikkita uy objectini yaratishimiz mumkin.

Demak:

Class → loyiha
Object → loyiha asosida yaratilgan uy

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Class ichidagi o‘zgaruvchilar¶

Class ichida yaratilgan o‘zgaruvchilar field yoki instance variable deyiladi.

Masalan:

class Student {
    String ism;
    int yosh;
}

Bu yerda:

ism
yosh

Student classining fieldlari.

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Student class¶

Keling, o‘quvchi uchun class yaratamiz.

class Student {
    String ism;
    int yosh;

    void tanishtir() {
        System.out.println("Mening ismim " + ism);
        System.out.println("Yoshim " + yosh);
    }
}

Keyin object yaratamiz:

Student talaba = new Student();

talaba.ism = "Ali";
talaba.yosh = 18;

talaba.tanishtir();

Natija:

Mening ismim Ali
Yoshim 18

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Bitta classdan ko‘p object¶

Masalan:

Student talaba1 = new Student();
Student talaba2 = new Student();

talaba1.ism = "Ali";
talaba1.yosh = 18;

talaba2.ism = "Vali";
talaba2.yosh = 20;

Har bir objectning o‘z ma'lumotlari bo‘ladi.

talaba1 → Ali, 18
talaba2 → Vali, 20

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new nima?¶

Object yaratishda new ishlatiladi.

Masalan:

Car mashina = new Car();

Bu:

Car classidan yangi object yarat

degan ma'noni anglatadi.

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this haqida qisqacha¶

Class ichida ba'zan objectning o‘z fieldiga murojaat qilish uchun this ishlatiladi.

Masalan:

class Student {

    String ism;

    void ismniChiqar() {
        System.out.println(this.ism);
    }
}

Bu yerda:

this.ism

joriy objectning ism fieldini bildiradi.

Hozircha thisni chuqur o‘rganish shart emas.

Keyingi bobda constructor bilan ishlaganda thisdan ko‘proq foydalanamiz.

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Class va object o‘rtasidagi farq¶

Class	Object
Qolip	Haqiqiy obyekt
Reja	Shu reja asosidagi narsa
O‘zi ma'lumot saqlamaydi	O‘z ma'lumotlariga ega
Car	mashina1

Masalan:

class Car {
    String model;
}

Bu class.

Car mashina = new Car();

Bu esa object.

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Amaliy mashqlar¶

1-mashq¶

Student classini yarating.

Unda:

ism
yosh

fieldlari bo‘lsin.

Keyin object yaratib, qiymat bering.

2-mashq¶

Car classini yarating.

Unda:

model
rang

fieldlari bo‘lsin.

Keyin ikkita object yarating.

3-mashq¶

Book classini yarating.

Unda:

nom
muallif
sahifalar

ma'lumotlari bo‘lsin.

4-mashq¶

Person classini yarating.

Unda salomBer() methodi bo‘lsin.

Method chaqirilganda:

Salom!

chiqsin.

5-mashq¶

Student classiga tanishtir() methodini qo‘shing.

Masalan:

Ism: Ali
Yosh: 18

ko‘rinishida ma'lumot chiqarsin.

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Muhim narsalarni eslab qoling¶

Class — object yaratish uchun qolip.

Object — class asosida yaratilgan narsa.

Object yaratish:

Car mashina = new Car();

Object fieldiga murojaat qilish:

mashina.model

Object methodini chaqirish:

mashina.yur();

Bitta classdan bir nechta object yaratish mumkin.

Keyingi bobda Constructor yordamida object yaratilganda unga boshlang‘ich qiymat berishni o‘rganamiz.