How to Implement the equals() Method

Quoting Javadoc for equals() method: The equals method implements an equivalence relation on non-null object references. […] If your equals() method does not satisfy the requirements, horrible things can happen because you no longer have this nice partitioning. This can lead to bugs that are very subtle and very tricky to debug.

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Finding Your DB2 Version

Do you know how to determine what version of DB2 you're using? It's not intuitive. […] There are a couple of methods you can use to determine the version of DB2. Why not just learn one?

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Implementing equals() and hashCode()

Let's begin with a puzzle. What is the output of this program? [&helip;] Why? What happened? Well, it's one of the most common Java mistakes.We violated the fundamental requirement for the hashCode() method.

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OneWebSQL and Maven 1.x

OneWebSQL supports Maven 2.x out of box. But a few weeks ago, one of our clients sent us a question: "I don't wanna migrate to Maven 2, do you support Maven 1?" Hm, we thought, the older Maven is retired, it's still in use. Let's see how we can get this done.

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SQL Course Table of Contents

Links to all SQL Course posts.

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SQL Course - Part 1. Introduction

Today we're starting a series of posts on the SQL language.

SQL (Structured Query Language) is a language for accessing data in databases. Informally, the word "database" has two meanings:

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