import java.util.*; //We are importing the ArrayList class from the util package!



public class ArrayListTest

{

	//The data member, which is our ArrayList

	private ArrayList arrLst;



	//This is the first time we are using the Constructor

	//to actually do something. In this case,

	//We are using it to create the ArrayList object.

	//It is very common to use the constructor to initialize

	//our Object's Data Members.

	public ArrayListTest()

	{

		arrLst=new ArrayList();

	}





	public void addWord(String s)

	{

		//Note: The class "Object" is the universal

		//object. It is the parent of ALL other Objects

		//in Java. Therefore due to Polymorphism,

		//We can use it as a reference to ANY object.

		//Normally it is only used in cases where you

		//need to reference multiple types of objects

		//that do not share any other common parent class

		//or interface. The ArrayList class

		//uses Object for the Add and Get methods

		//so that you can store any type of object in the collection.

		//Here's the add methods signature right from the Java Doc (JDK 1.4.2):

		//public boolean add(Object o)

		//The add method "appends" to the end of the list...

		arrLst.add(s);

	}





	public void printAll()

	{

		String s;



		//We are going to use a for loop

		//to loop from element 0 to the SIZE of the arraylist.

		//The method "size()" returns an int representing the

		//number of elements added to and are current contained

		//within the arraylist.

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

		{

			//The "get" method will return

			//the Object to us. We need to type case

			//the Object back to the String object.

			s=(String)arrLst.get(i);



			//Print out the String on it's own line.

			System.out.println(s);

		}

	}





	//This method will remove

	//an element from the ArrayList

	//at the given index.

	public void removeWordAt(int index)

	{

		//We should only remove from the array list

		//if the index is a valid index within the Array List.

		//This is why we are checking if the value of index

		//is between 0 and the size of the array list.

		if (index>=0 && index<arrLst.size())

		{

			//If the index is valid

			//Do the actual removal.

			arrLst.remove(index);

		}

	}





	//Just a wrapper method around

	//the "clear()" method of array list

	//which will REMOVE all elements from the list.

	public void clearAllWords()

	{

		arrLst.clear();

	}





	public static void main(String[] args)

	{

		//Create a new ArrayListTest object to use

		ArrayListTest alTest=new ArrayListTest();



		//Add Strings to my array list using the addWord

		//method on the ArrayListTest class we just created...

		alTest.addWord("Hello");

		alTest.addWord("World");

		alTest.addWord("This");

		alTest.addWord("Is");

		alTest.addWord("My");

		alTest.addWord("First");

		alTest.addWord("Test");

		alTest.addWord("With");

		alTest.addWord("ArrayLists!");



		//Use the print all method on the ArrayListTest

		//class we created to print each word we added

		//on it's own line on the screen.

		alTest.printAll();





		//Print a blank like to separate output!

		System.out.println();





		//Let's test the remove method and remove word "First"

		//which if we count is the 6th element which is array index 5.

		//We need to use array index 5 instead of the actual element number

		//index the first element in the array list is called element 0 not 1!

		//Basically as we mentioned many times, ArrayList is basically a

		//growable array!

		alTest.removeWordAt(5);



		//Let's print again, to show the changes to the list!

		alTest.printAll();





		//Since we are done with the list.

		//It's good practice to clear the list.

		//This helps Java clear the memory of unused data FASTER.

		alTest.clearAllWords();

	}

}