Tag: implementation

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...

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...