From Hell To Heaven: Increase app’s performance with Redis

Welcome to my new series “From Hell To Heaven“. These series will be about different cases of programmers dealing with issues that anyone can find in a typical day. In this first post, we will be implementing Redis as a second level cache layer using Spring Boot.

Introduction

I have been working on a couple of projects and encountered several performance issues. This issue relied mostly on reading the same data multiple times in the same endpoint. Using second layer cache is a common solution to this issue and that’s what we are going to do today! You will see how easy it will be to integrate Redis as a cache layer using Spring boot. Read more...

SurveyJS – Learn how to create easy surveys

As background story, I finished university with a graduation project for a company, which you can find it here. The goal was to do something similar to Google Forms integrated with an ISO 9001 document management system, so I needed a good library to build surveys. It had to meet the following requirements:

Good Documentation JSON-based library Custom CSS Send data to a server or at least provided a method

After intensive research, I encountered many libraries but they didn’t meet at least one requirement, except for SurveyJS. It has complete documentation with examples and provided helper methods to get data, therefore I decided to use it. After finishing the project, I thought it would nice to post the implementation applied to a production project, so let’s get started! Read more...

Learning Gulp Basics | Javascript

In the past trimester, I was given a project of creating anything with MEAN.JS and it was the first time I used gulp, so I decided it was time to learn more about what gulp is and how does it work; with the help with a friend I understood how it worked. So now, let’s get started with gulp basics:

What is Gulp?

Gulp is a task runner and build system that uses the philosophy of code over configuration (I’m looking at you, Grunt!). At first glance, I had no idea what was happening in that gulpfile.js, but then I started reading and noticed very interesting things, like it’s simplicity for starters. You will mainly use four functions: Read more...

Binary Search | Search Algorithm

The theory

A binary search algorithm is a search algorithm that uses the concept of divide and conquer in order to find a target value’s position. Basically, this search algorithm compares the target value with the middle element of the collection.

If it is equal, return the position. If it is not equal, then we will need to check if the value is either greater or less than the target value. This is to know what side of the collection we need to split.

Binary Search Requirements

There’s a condition applied to the binary search array, which is that the array must be sorted. This is because it uses the value (in our case an integer), to compare and check if the selected position has the target value or check where to go.

Binary Search Array Algorithm

Implementation

First things first, we will create our binary search class with the search methods.

public class BinarySearch { public int search(int[] array, int number) { return search(array, number, 0, array.length); } private int search(int[] array, int target, int start, int end) { int mid = (start + end) / 2; if (end < start) { return -1; } if (array[mid] == target) { return mid; } else if (array[mid] > target) { return search(array, target, 0, mid - 1); } else { return search(array, target, mid + 1, end); } } } Read more...

Modifying and Updating a JAR File| Java

A Brief Introduction…

It all started when a co-worker asked for help when trying to update an IP Address of a java API, however, he only had the JAR file available. With another co-worker, we dug up the internet and tried to find a way to do this, and we finally did. I thought of sharing what we acquire for any future help.

Requirements

In order to do any of the operations mentioned in the title, you will need to have java and JDK installed, a desired jar you want to modify, and basic knowledge of commands for the terminal. In order to get the .java file from the JAR, I would recommend a program called JD-GUI. You will just need to open the jar file, and look for a desired file and save it. Read more...

Linked List | Data Structures

A brief introduction

Linked List is a linear collection of objects, which is composed of nodes pointing to the next node. Each node contains a value and a reference to the next node in the sequence. Most of the operations applied in a linked list (add, remove, search, etc.) will require sequencial scanning most of the time.

single-linked-list
As you can notice, each node will always have a pointer to the next node and a value, this is called a single linked list. If a node has a link to the previous and to the next one, it is called a double linked list or a circular linked list.

Implementation

The first step will be creating a node class:

public class Node<T>{

    private Node next;
    private T value;

    public Node(){
        
    }
    
    public Node(T value){
        this.value = value;
    }
    
    public Node getNext() {
        return next;
    }

    public void setNext(Node next) {
        this.next = next;
    }

    public T getValue() {
        return value;
    }

    public void setValue(T value) {
        this.value = value;
    }
}

This is a POJO (Plain Old Java Object) of a Node class, which contains a value and another Node that will be the “Next” node. If you ask yourself about the “T” I have in there, I am declaring the Node class as Generic, enabling the option to choose what datatype to use. Now, we will be creating varios operations used, starting with the add.

public class MyLinkedList<T>{ private Node head; private static int counter; public void add(T value){ if (head == null) { head = new Node(value); } else { Node temp = new Node(value); Node current = head; while (current.getNext() != null) { current = current.getNext(); } current.setNext(temp); } counter++; } } Read more...

Activity Class | Android Tutorials #3

After creating an android project, the first thing you will notice is the activity class. An activity is the primary class for user interaction, it is a single-focused task that a user can do.

Activity Class

Each activity should be modular and support one-focused thing a user can do in an app. For example, one that handles only the login of your application. It handles and takes care of the UI you will need for that specific window, using setContentView(view)

Activity Life Cycle

In simple words, an activity can be divided in three states: Read more...

Creating a new project | Android Tutorials #2

In the previous lesson, we learn about the different kind of IDEs that exist for android development. Now, we will be using Android Studio to create a project and review each file and folder created, and thinks to consider.

Before we begin…

If you have not downloaded Android Studio, you can download it from here. We will also need JDK (Java Development Kit), which you can download from here, and we need Android SDK, which is already included with the Android Studio. After downloading and installing, we are more than ready to begin this lesson. Read more...

IDEs Overview | Android Tutorials #1

In this tutorial, I will be writing an overview of different IDEs and Frameworks that exists for android development. At the end of this post, you will find several links that could be useful.

Eclipse

The first IDE we will be looking at is Eclipse, that’s where it started. Eclipse has an android plugin (ADT Plugin), which the last update occurred in mid 2015. I have not gone into deep waters with eclipse and android, however, there has been support issues with it. I wouldn’t recommend starting with this. Read more...

Coming Soon – Android tutorials

I know it is a long time since my last post, I have been busy with university and currently making an android application from scratch. It has been a tough ride through the android world, I have learn a lot these couple of months and I will be preparing several tutorials about android, will do my best to make this understandable and easy to learn.

I will be starting with the very basics of android programming, talking about IDEs, where to begin, etc… I am eager to start this series and teach what I have been learning. Read more...