- java 7, 8, 9 代表 product version
- 1.7, 1.8, 1.9 代表 developer version
实际上是同一个版本
Both version numbers “1.5.0” and “5.0” are used to identify this release of the Java 2 Platform Standard Edition. Version “5.0” is the product version, while “1.5.0” is the developer version. The number “5.0” is used to better reflect the level of maturity, stability, scalability and security of the J2SE.
This correspondence continued through later releases (Java 6 = JDK 1.6, Java 7 = JDK 1.7, and so on).