The first part of a series on the Java Collections Framework, an absolutely vital set of classes for organising data in your code. In this part we’ll look at ArrayList; an expandable array. ArrayList is probably the most used and easiest to use member of the collections framework.

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Code For This Tutorial

App.java:

import java.util.ArrayList;
import java.util.List;

public class App {

	public static void main(String[] args) {
		ArrayList<Integer> numbers = new ArrayList<Integer>();

		// Adding
		numbers.add(10);
		numbers.add(100);
		numbers.add(40);

		// Retrieving
		System.out.println(numbers.get(0));

		System.out.println("\nIteration #1: ");
		// Indexed for loop iteration
		for (int i = 0; i < numbers.size(); i++) {
			System.out.println(numbers.get(i));
		}

		// Removing items (careful!)
		numbers.remove(numbers.size() - 1);

		// This is VERY slow
		numbers.remove(0);

		System.out.println("\nIteration #2: ");
		for (Integer value : numbers) {
			System.out.println(value);
		}

		// List interface ...
		List<String> values = new ArrayList<String>();
	}
}

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