Collection : ArrayList Example

Collection : ArrayList Example

This tutorial contains description of Collection ArrayList with example.

ArrayList :

For ArrayList<E> import java.utill.ArrayList. It provides expandable arrays that is it supports dynamic array.
It can automatically grow when you add new element and it shrink when you delete any element.
Size of standard arrays are fixed which is defined at the time of array creation, which cause problem when
you don't know the number of elements to add. For such condition, the Collection Framework provides ArrayList which can be dynamically increase or decrease in length.

Some method of ArrayList -

add(Object o) - It adds the specified element at the end of the list.
add(int index,Object element) - By using this method you can add specified element the specified position in ArrayList.
remove(int index) - Removes the element at the specified index from the Arraylist.

Example :

package collection;

import java.util.ArrayList;

class ArrayListExample {
public static void main(String[] args) {
// Creating ArrayList of Integer
ArrayList<Integer> list = new ArrayList<Integer>();
int size;
size = list.size();
System.out.println("Initial size of ArrayList : " + size);

// Adding elements in ArrayList
list.add(333);
list.add(400);
list.add(200);
list.add(1, 999);

size = list.size();
System.out.println("Size of ArrayList after adding elements : " + size);
System.out.println("Elements of ArrayList : ");
for (int i = 0; i < size; i++) {
System.out.println(list.get(i));
}

// Removing element from ArrayList
list.remove(3);
size = list.size();
System.out.println("Size of ArrayList after removing elements : "
+ size);
System.out.println("Elements of ArrayList : ");
for (int i = 0; i < size; i++) {
System.out.println(list.get(i));
}
}
}

Description : In this example we are creating ArrayList and using its some methods. We are creating ArrayList list for Integers as -
ArrayList<Integer> list = new ArrayList<Integer>();
size() method returns size of the list. Initially size of ArrayList is zero. It means list has no element. Next by calling add() method we can add any number of elements. We can print list elements by get() method ,using for loop.
For removing element from list we can call remove() mehod.

Output :

Initial size of ArrayList : 0
Size of ArrayList after adding elements : 4
Elements of ArrayList : 
333
999
400
200
Size of ArrayList after removing elements : 3
Elements of ArrayList : 
333
999
400