Core Java

A WeakHashMap in Java is a pretty popular data-structure among mid to senior-level Java developers. The WeakHashMap class is present in the java.util package. It’s a Map implementation which stores weak references to its keys. An entry in a WeakHashMap gets automatically removed when the associated key loses all of its active strong and soft references. In this post, we’ll first ...

This is part 7 of the series called “Functional Java by Example”. The example I’m evolving in each part of the series is some kind of “feed handler” which processes documents. We’ve already dealt with exceptional situations before, but we’re going to take care of them, more ehm,…functionally — as data. If you came for the first time, it’s best ...

Not many examples show this, but how you use JAXB in your application can make a huge difference in the performance (and memory usage). The example In this blog post I’ll use an example Object called Membership that looks something like this: We will marshal and unmarshal this object to and from XML using JAXB. Create the context in a ...

This post features five (mostly well-known) refactoring principles applied when refactoring real open-source code (Gradle Modules Plugin). Context When I worked on separate compilation of module-info.java for Gradle Modules Plugin (PR #73), I noticed potential for some refactoring. As a result, I filed issue #79 and later resolved it with PR #88 (not merged yet), where I refactored the code. ...

Liam Miller-Cushon has published a document simply called “Equivalence” in which he proposes “to create a library solution to help produce readable, correct, and performant implementations of equals() and hashCode().” In this post, I summarize some reasons why I believe this proposal is worth reading for most Java developers even if the proposal never gets implemented and why the proposal’s ...

Introduction: Iterators in Java are used to traverse elements of a given source. Spliterator in Java is one among the four available Java Iterators – Iterator, Enumeration, ListIterator, and Spliterator. It is an interface available in java.util package. Spliterator was first introduced in Java 8 to support parallel programming. However, we can use it for both sequential and parallel processing ...

In one of my previous articles, we saw how to create QRCode and its SVG equivalent using Zxing Java library. The Zxing library is no longer actively maintained and for this, there is a wrapper around Zxing library called QRGen, which provides much higher level APIs and a builder syntax for generating QR Codes. In this article, we will see ...

Project Skara was created “to … investigate alternative SCM and code review options for the JDK source code, including options based upon Git rather than Mercurial, and including options hosted by third parties.” The OpenJDK skara-dev mailing list included a post from Robin Westberg last week that announced, “We have added some additional read-only mirrors of a few different OpenJDK ...

In this article, we will look at how to use the Zxing QR code generation library and JFreeSVG library to create a QR Code SVG image in Java. QR Code Generation The below code creates a java.awt.image.BufferedImage object representing QR Code using Zxing library: 1 public static BufferedImage getQRCode(String targetUrl, int width,     int height) {     try {         Hashtable<EncodeHintType, Object> hintMap ...