This tutorial came to be due to a question I found on Stackoverflow titled Mechanism behind QR code scanning of whatsapp webapp and the investigation and answer that I gave . Because the answer was given in real broad strokes, I decided to create a tutorial on how to implement something...
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A very common question from beginners in Java is "What does Static means" or "What is Static in Java". It is actually very simple. Something that is Static in Java is something that belongs to the Class and not the objects of that Class type, hence it is shared across...
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Introduction If Statement Equality Operators Conditional Operators Else Not Switch Statement Wrapping up References Introduction This is where the fun part begins! With the previous tutorials we have and idea of the core building blocks, now we start looking at the implementation of flow control, or logic if you will....
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Introduction Arrays Lets talk Arrays Accessing values of an Array Setting values of elements Initing with values What is the size of this array? Accessing using invalid index References Introduction At this point we have all the knowledge we need to create Classes, methods, variables, instances of Objects, call methods,...
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Introduction Packages Overloading this Keyword Continuing the code Calling methods from Anywhere Access Modifiers Public Private Package-Protected Protected Using Access Modifiers What about Constructors? What about Methods Level Scope Variables? Many objects Introduction In this tutorial we'll finally look at Packages to organize our code, and also at Access Modifiers...
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Introduction Variables Scope Classes and Objects Creating methods Setter Methods Getter Methods Constructors Exercise What else about methods? Introduction In the previous tutorials we dabbed into Primitive variables, did a few operations with them, nothing special or exciting. In this tutorial however, we'll now look at Objects and Reference Variables,...
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Introduction My First Variable Primitive Variables Some operator action and Strings Introduction On the previous tutorial we made a really simple program, with just one Class and one Method. There was no data stored, no calculations done, etc. In this tutorial we will look into storing data and doing something...
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Introduction Hello World Java and Javac Looking at the Code A Class A Method Exercises Introduction To start this great journey, we'll use the typical "Hello World" program. Yes, it is not very exciting, not very motivational, but before we start running we must learn how to walk. At this...
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Introduction Object-Oriented Programming (OO) Language Platform Development Kit IDEs Next Steps Introduction Java is not a difficult language to learn, even if you are a complete beginner. There are a few concept however that we must get out of the way in order to get started. In this tutorial we...
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To add an image to an already existing PDF file is a relatively simple task, using iText. On this example, we will add a smile image to the bottom of the PDF first page. We start by loading the PDF we want to modify, and getting the reference for the...
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Today we're going to show how to read a XML file and convert it's entries to lines on an excel file. The XML file is located at https://github.com/jbaysolutions/xml-to-excel/blob/master/Publication1.xml?raw=true. The XML file's main nodes are "Substances", each one has a few...
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From an Activity To start a new Activity from another Activity: Intent intent = new Intent(this, OtherActivity.class); startActivity(intent); From a Service Intent intent = new Intent(this, OtherActivity.class); intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); startActivity(intent); (adsbygoogle = window.adsbygoogle || []).push({}); From somewhere else To start an Activity...
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On one of our projects, we were asked to implement a process that updates a database with values from an Excel file on a daily basis. The file is located at https://github.com/jbaysolutions/excel-xml-reader/raw/master/ActiveSubstance.xls. The problem with this file is its format. It's an...
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If you are following the tutorials here you must be dying to do some queries using JPA. So, before we go any further into other aspects of JPA, lets query the model! For this task, instead of using SQL we will be using the Java Persistence Query Language or also...
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We have just covered the subject of Many-To-Many relationships, which is a fun topic for the hole family! Now there are some particular cases on the Many-to-many front which are not particularly hard, but can lead to a bit of confusion. One of those particular cases is the M2M with...
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