Mavzu. Standart algoritmlar va iteratorlari mavzu. Konteynerlar

Method	Description
Try it
addFirst()	Adds an item to the beginning of the list.	Try it »
addLast()	Add an item to the end of the list	Try it »
removeFirst()	Remove an item from the beginning of the list.	Try it »
removeLast()	Remove an item from the end of the list	Try it »
getFirst()	Get the item at the beginning of the list	Try it »
getLast()	Get the item at the end of the list

Java iterator

An - bu ArrayList va HashSetIterator kabi to'plamlar bo'ylab aylanish uchun ishlatilishi mumkin bo'lgan ob'ekt . U "iterator" deb ataladi, chunki "iteratsiya" tsikl uchun texnik atamadir.
Iteratordan foydalanish uchun uni paketdan import qilishingiz kerak java.util.

Iteratorni olish

Usul har qanday to'plam uchun iterator()olish uchun ishlatilishi mumkin Iterator:

Misol

// Import the ArrayList class and the Iterator class
import java.util.ArrayList;
import java.util.Iterator;

public class Main {

public static void main(String[] args) {

// Make a collection

ArrayList cars = new ArrayList();
cars.add("Volvo");
cars.add("BMW");
cars.add("Ford");
cars.add("Mazda");

// Get the iterator

Iterator it = cars.iterator();

// Print the first item

System.out.println(it.next());
}
}

To'plam orqali aylanish

To'plamni aylanib chiqish uchun quyidagi hasNext()va next()usullaridan foydalaning Iterator:

Misol

while(it.hasNext()) {
System.out.println(it.next());
}

To'plamdan elementlarni olib tashlash

Iteratorlar ular orqali o'tadigan to'plamlarni osongina o'zgartirish uchun mo'ljallangan. Usul remove()tsikl paytida to'plamdan elementlarni olib tashlashi mumkin.

Misol

To'plamdan 10 dan kichik raqamlarni olib tashlash uchun iteratordan foydalaning:
import java.util.ArrayList;
import java.util.Iterator;

public class Main {

public static void main(String[] args) {
ArrayList numbers = new ArrayList();
numbers.add(12);
numbers.add(8);
numbers.add(2);
numbers.add(23);
Iterator it = numbers.iterator();
while(it.hasNext()) {
Integer i = it.next();
if(i < 10) {
it.remove();
}
}
System.out.println(numbers);
}
}
Eslatma: For yoki har bir sikl yordamida elementlarni o‘chirishga urinish to‘g‘ri ishlamaydi, chunki to‘plam bir vaqtning o‘zida o‘lchamini o‘zgartirib, kod siklamoqchi bo‘ladi.