Java versioning
There have been many changes made to the Java versioning scheme and schedule over its history. One first thing to note is that, at the very beginning, Java versioning used to follow a 1.x scheme, with 1.3 essentially being the first widespread version.
Since version 1.5, however, the versioning scheme ditched the 1.x prefix, so we had Java 5, 6, and so on.
Another important point to make is about naming. The very first versions were called JDKs (short for Java Development Kit – more about this in a bit). Then, from versions 1.2 to 5, the platform was named J2SE (for Java 2 Standard Edition). Since Java 6, at the time of writing, the platform is referred to as Java SE (for Java Standard Edition).
The most important thing to know about the JDK, a term that most of us are familiar with, is that until Java 8, the Java platform was distributed in two versions, the Java Runtime Environment (JRE) and the JDK. The JRE was basically a stripped-down version of...