The number "5.0" was arrived at by dropping the leading "1." from "1.5.0". Where you might have expected to see 1.5.0, it is now 5.0 (and where it was 1.5, it is now 5).
Version 5.0 is used in the platform and product names as given in this table:
|Platform name||JavaTM 2 Platform Standard Edition 5.0||J2SETM 5.0|
under the platform
|J2SETM Development Kit 5.0||JDKTM 5.0|
|J2SETM Runtime Environment 5.0||JRE 5.0|
Due to significant popularity within the Java developer community, the development kit has reverted back to the name "JDK" from "Java 2 SDK" (or "J2SDK"), and the runtime environment has reverted back to "JRE" from "J2RE". Notice that "JDK" stands for "J2SE Development Kit" (to distinguish it from the J2EE Development Kit). The name "Java Development Kit" is no longer used, and has not been offically used since 1.1, prior to the advent of J2EE and J2ME.
As before, the "2" in Java 2 Platform Standard Edition indicates the 2nd generation Java platform, introduced with J2SE 1.2. This generation number is also used with J2EE and J2ME.
J2SE also keeps the version number 1.5.0 (or 1.5) in some places that are visible only to developers, or where the version number is parsed by programs. As mentioned, 1.5.0 refers to exactly the same platform and products numbered 5.0. Version numbers 1.5.0 and 1.5 are used at: