찾으시는 정보가 있으시다면
주제별reference를 이용하시거나
우측 상단에 있는 검색기능을 이용해주세요

ArrayList

Is a resizable array

Elements can be added and removed from an ArrayList whenever you want

import java.util.ArrayList;
import java.util.Collections;
public class Main {
  public static void main(String[] args) {
    // Elements in an ArrayList are actually object.
    // To use primitive type, you must specify an equivalent wrapper class
    ArrayList<Integer> myNumbers = new ArrayList<Integer>();	// Create an ArrayList object
    myNumbers.clear();		// to remove all
    myNumbers.add(33);		// add item, (item)
    myNumbers.add(12);
    myNumbers.add(12);
    myNumbers.get(1);	// to access an element, (index)
    myNumbers.set(1, 22);	// to change item, (index, item)
    myNumbers.remove(2);	// to remove item, (index)
    myNumbers.size();		// to find out how many elements have
    Collections.sort(myNumbers);  // Sort myNumbers
    for (int i : myNumbers) {	// Loop through
      System.out.print(i + “ ”);
    }	// output will be 22 23
  }
}

LinkedList vs ArrayList

LinkedList is almost identical to the ArrayList

How the ArrayList works

• ArrayList class has a regular array inside it

• When an element is added, it is placed into the array

• If the array is not big enough, a new, larger array is created to replace the old one

• And old one is removed

How the LinkedList works

• LinkedList stores its items in containers.

• The list has a link to the first container and each container has a link to the next container in the list

• To add an element to the list, the element is placed into a new container

When to use

• ArrayList for storing and accessing data

• LinkedList to manipulate data

Methods

addFirst() : Adds an item to the beginning of the list

addLast() : Add an item to the end of the list

removeFirst() : Remove an item from the beginning of the list

removeLast() : Remove and item from the end of the list

getFirst() : Get the item at the beginning of the list

getLast() : Get the item at the end of the list