Before JDK 9, the JDK versioning scheme was not intuitive to developers and was not easy for programs to parse. Looking at the two JDK versions, you could not tell the subtle differences between them. It was hard to answer a simple question: Which release contains the most recent security fixes, JDK 7 Update 55 or JDK 7 Update 60? The answer was not the obvious one, which you may have guessed—JDK 7 Update 60. Both releases contain the same security fixes. What is the difference between the JDK 8 Update 66, 1.8.0_66, and JDK 8u66 releases? They represent the same release. It was necessary to understand the versioning scheme in detail before you could understand the details contained in the version string. JDK 9 attempts to standardize the JDK versioning scheme, so it can be easily understood by humans, easily parsed by programs, and follows the industry-standard versioning scheme.