Question

Hi. Can you give me some examples of how can I create a list in Java and some of it's methods (adding/removing elements to it)?

Thanks

Answer 1

First you can read about Java collections here: https://docs.oracle.com/javase/8/docs/technotes/guides/collections/overview.html

Interface	Hash Table	Resizable Array	Balanced Tree	Linked List	Hash Table + Linked List
Set	HashSet		TreeSet		LinkedHashSet
List		ArrayList		LinkedList
Deque		ArrayDeque		LinkedList
Map	HashMap		TreeMap		LinkedHashMap

Classes that implement the collection interfaces typically have names in the form of <Implementation-style><Interface>.

In my code you will find some good examples of the usage of Lists in Java:

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

public class ArrayListCode {
    public static void main(String[] args) {
        List<String> listOne = new ArrayList<>();//ArrayLists are like resizable arrays
        listOne.add("USA");
        listOne.add("United Kingdom");
        listOne.add("France");
        listOne.add("Italy");

        System.out.println(listOne);

        listOne.add("Bulgaria");
        System.out.println(listOne);

        listOne.remove(0);//WHICH ELEMENT IN THE LIST TO REMOVE - IN THIS CASE IT WILL BE "USA"
        System.out.println(listOne);

        String country = listOne.get(1);//WHICH ELEMENT TO GET FROM THE LIST
        System.out.println("The second country is: " + country);

        int pos = listOne.indexOf("Italy");//WHICH IS THE POSITION OF "Italy"
        System.out.println("The position of Italy in the ArrayList is: " + pos);
    }
}

• On line 14: you can see how to add an element to the list using the method .add()
• On line 17: you can see how to remove a particular element from certain position in the list by using the method .remove()
• On line 20: you can see how to show particular element from a certain position in the list with the method .get()
• On line 23: you can see how to show a particular position of a certain element in the list with the method .indexOf()

Also, this page will explain more about the lists in Java: http://docs.oracle.com/javase/8/docs/api/java/util/List.html

The output:

[USA, United Kingdom, France, Italy]
[USA, United Kingdom, France, Italy, Bulgaria]
[United Kingdom, France, Italy, Bulgaria]
The second country is: France
The position of Italy in the ArrayList is: 2

Answer 2

To understand better the collections in Java, watch these tutorials:

https://www.youtube.com/watch?v=mkCTxtLe7XU

Here is the link to the playlist with all the videos about the various collections in Java with nice visual explanations (13 videos): https://www.youtube.com/playlist?list=PLB841C370FAFB8EC7