ARRAY vs ARRAYLIST

ARRAY vs ARRAYLIST

Array is an object used to save similar data type elements and its size is limited.

Array is static in nature. Once created we cannot change size of array.

• ·       Random access, linear data structure

• ·       Fixed size once created

• ·       Can contain objects and primitives

• ·       Must declare element type

• ·       It is not a class

• ·       Elements accessible with index number

Eg: int[] ar=new int[3]; //stores complete integer types

Arraylist is a part of Collection Framework of util package to store different data type objects and it is growable. Arraylist is dynamic in nature. It can be re-size itself when needed depending upon capacity and load factor.

• ·       Random access, linear data structure

• ·       Dynamic size, grows automatically

• ·       Can only contain objects

• ·       Element type  is OBJECT

• ·       It is a class with many methods

• ·       Accessing methods like get() etc are available

Eg: Arraylist arr=new Arraylist();

       arr.add(13); //integer type

       arr.add(13); //string type

ArrayList<String> stringList = new ArrayList<String>(); //Generic ArrayList to Store only String objects

The Methods Of ArrayList class are:
1)Add - stringList.add(“item”);
2)Remove- stringList.remove(0);
3)Clear- stingList.clear();
4)Insert
5)TrimToSize
6)Sort
7)Reverse 

Example:

import java.util.ArrayList;

public class Program

{

          public static void main(String[] args)

          {

// Create new ArrayList.

                              ArrayList<Integer> elements = new ArrayList<>();

// Add three elements.

                              elements.add(10);

                              elements.add(15);

                              elements.add(20);

// Get size and display.

                              int count = elements.size();

                              System.out.println("Count: " + count);

// Loop through elements.

                              for (int i = 0; i < elements.size(); i++)

{

                                          int value = elements.get(i);

                                          System.out.println("Element: " + value);

                              }

          }

}

Output

Count: 3

Element: 10

Element: 15

Element: 20