ArrayList in Java

Java API provides several predefined data structure which are also known as collections in Java.ArrayList is a collection which we can use conveniently in place of array because when we are using array there is a problem that array size cannot be changed automatically at runtime i.e. if we are using an array and it became full then it will throw an exception instead of increasing its size.This problem can be solved by using ArrayList.There are also other benefits as there are lot of inbuilt methods which are convenient to use for adding element,deleting an element,searching an element etc.List can also contain null and duplicate elements.So lets get some knowledge of methods of ArrayList.
1)add(element):This method is used to add an element at the last position of ArrayList.This is an efficient method to add an element in ArrayList.
2)add(index,element):This method is used to add an element at the specified position in the ArrayList.This method is not so much efficient as the elements after that position have to shift one position.
for ex list=2,3,6,7
list.add(2,56); //add 56 at 2nd position
 then list=2,3,56,6,7
So whenever possible use add(element) method for efficeincy.
3)addAll(Collection<?extends E>):This method is used to append all the elements of other collection at the end of the list.
4)addAll(index,Collection<?extends E>):This method is used to append all elements of other collection at specific position in the list.

Program Code:
package examples;

import java.util.ArrayList;

public class ArrayListExample {

public static void main(String[] args) {

ArrayList<String> list=new ArrayList<String>();
System.out.println("This is an example of add method in ArrayList");
list.add("First List");
System.out.println("After adding elements list is "+list );
list.add(1, "I");
System.out.println("After adding elements list is "+list );
list.add(0, "Abhishek");
System.out.println("After adding elements list is "+list );
System.out.println("List can also contain duplicate elements");
list.add("I");
System.out.println("After adding elements list is "+list );

ArrayList<String> list1=new ArrayList<String>();
list1.add("Second List");
System.out.println("After adding elements list is "+list1 );
list1.addAll(list);
System.out.println("We can append other list to this list");
System.out.println("After appending other list, elements of list are "+list1 );

ArrayList<String> list2=new ArrayList<String>();
list2.add("Third List");
list2.add("Hello");
System.out.println("We can also insert other list at specific location");
list2.addAll(1, list1);
System.out.println("After appending other list, elements of list are "+list2 );

}

}

Output:
This is an example of add method in ArrayList
After adding elements list is [First List]
After adding elements list is [First List, I]
After adding elements list is [Abhishek, First List, I]
List can also contain duplicate elements
After adding elements list is [Abhishek, First List, I, I]
After adding elements list is [Second List]
We can append other list to this list
After appending other list, elements of list are [Second List, Abhishek, First List, I, I]
We can also insert other list at specific location
After appending other list, elements of list are [Third List, Second List, Abhishek, First List, I, I, Hello]

So above are some methods to add elements in the ArrayList.
Hope everything is clear,if not then ask me via comments or email
Thanks.