Why import javax.swing.* instead of java.swing.*

Question

I did not understand why there is "x" appended to "java" for few of the import packages. What is the reason? Can't it be just java.swing.* like others java.io.*?

Answer 1

Swing was originally an extension to Java - a separately downloadable library. It became part of the "main" JRE in Java 1.2. It would have been odd for a separate library to have claimed a java.* package, hence the current situation. There are plenty of other extensions which have a similar story.

The Wikipedia article on Swing has a bit more information on its history.

Answer 2

From Core Java 2:
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The name javax indicates a Java extension package, not a core package. The Swing classes are indeed an extension to Java 1.1. Because the Swing classes were not part of the core hierarchy, it is possible to load the Swing classes into a Java 1.1-compatible browser.(the security manager of the browser does not allow adding any packages that start with "java.".) On the Java 2 platform, the Swing package is no longer an extension, but is instead part of the core hierarchy. Any Java implementation that is compatible with Java 2 must supply the Swing classes. Nevertheless, the javax name remains, for compatibility with Java 1.1 code. (Actually, the Swing package started out as com.sun.java.swing, then briefly got moved to java.awt.swing during early Java 2 beta versions, then went back to com.sun.java.swing in late Java 2 beta versions, and after howls of protest by Java programmers, found its final resting place in javax.swing.)