ArrayList in java

ArrayList is a collection of data items that grows and shrinks depending on the number of data items present in it, you can think it as a dynamic array or a link lists in C, whose size increases when we insert a data and decreases as delete some data from it.

To insert a data item we use add() method and to delete we use remove() method as demonstrated below in line 13 and 20 respectively.

following code shows how we can use ArrayList in java

// file ArrayListDemo.java
import java.io.*;
import java.util.*;
public class ArrayListDemo{
	public static void main(String args[]) throws IOException{
		ArrayList<String> array_of_string=new ArrayList<String>();
		String str;
		int index;
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		System.out.println("Enter data  to insert in arraylist");
		//type "end" to stop
		while((str=br.readLine()).equalsIgnoreCase("end")==false){ //loop ends when user types "end"
			array_of_string.add(str); //adding data to arraylist
			System.out.println("Inserted a data size of arrayList is "+array_of_string.size());
		}
		System.out.println("\n------------\nEnter the index to delete data item");
		while(array_of_string.size()>0){
			index=Integer.parseInt(br.readLine());
			if(index>-1 && index<array_of_string.size()){
				array_of_string.remove(index); //deleting data from arraylist
				System.out.println("Item at "+index+" deleted now array contains "+array_of_string.size()+" elements");
			}
			else
				System.out.println("Enter a valid index");
		}
		System.out.println("Array is now empty");
	}
}

the output of above code will be

Enter data  to insert in arraylist
hello
Inserted a data size of arrayList is 1
hi
Inserted a data size of arrayList is 2
anyone
Inserted a data size of arrayList is 3
there?
Inserted a data size of arrayList is 4
no one ?
Inserted a data size of arrayList is 5
:(
Inserted a data size of arrayList is 6
end

------------
Enter the index to delete data item
6
Enter a valid index
5
Item at 5 deleted now array contains 5 elements
4
Item at 4 deleted now array contains 4 elements
3
Item at 3 deleted now array contains 3 elements
3
Enter a valid index
2
Item at 2 deleted now array contains 2 elements
1
Item at 1 deleted now array contains 1 elements
0
Item at 0 deleted now array contains 0 elements
Array is now empty