O'Reilly logo
  • Michael ss thinks this is interesting:

Note that the Swing package is defined in the javax package. In early versions of the JDK, all Java packages were defined in the java package. Now, many packages are defined in the javax package. The Swing package is one of them.

From

Cover of Java Programming

Note

换句话说,现在的很多包才在javax.开头的包中