understanding ArrayList

Understanding the concept of ArrayList :

Authors : Divyansh Pratap Singh (twitter)

Array List vs Array :

Array List	Array
they have variable size	they have fixed size
they have non-continous memory allocation	they have continous memory allocation
they can store only objects	they can store primitive data-types ex. int , float

Implementing ArrayList

    `import java.util.ArrayList;
    public class arrayy_list{
        public static void main(String[]args){

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

        }
    }
   `

Similarly for declaring String

ArrayList<String> name = new ArrayList<String>();

Adding element in ArrayList

we use add function to add an element in ArrayList

ArrayList<Integer> list = new ArrayList<Integer>();
list.add(3);

Adding elements 3,2,5,0 --> below is the complete code for adding element
'''
import java.util.ArrayList;
public class arrayy_list{
public static void main(String[]args){

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

            list.add(3);
            list.add(2);
            list.add(5);
            list.add(0);
        }
    }

`

Accessing elements of ArrayList :

to access element in ArrayList we use get function . Inside get function we pass the index position of the element .

list.get(0);

Gives us : 3

Adding element in middle of ArrayList :

add function adds an element at the end of the ArrayList ; to add element at any position in ArrayList we use add function and pass 2 parameters ;

list.add(<indexposition><element>);

list.add(0,9);

Result : [9,3,2,5,0]

Changing element in ArrayList :

to change a value in ArrayList we use set function . The function takes 2 parameters ; 1st is the index position of the element you want to change and the 2nd parameter is the new element.

list.set(0,8);

Result : [8,3,2,5,0]

removing an element from ArrayList :

to remove a element from ArrayList we use remove function and pass the element index position as the parameter.

list.remove(0);

Result : [3,2,5,0]

printing complete ArrayList

System.out.println(<ArrayList name >);
System.out.println(list);

Result : [3,2,5,0]