Eclipse: editing and running code live

When editing Java code in Eclipse I can modify the code while it's running in various ways and have those changes take effect without restarting my program.

What is the 开发者_开发知识库technology underlying this feature? Is it part of Eclipse, or is it something I can do with the command line tools and the tools that come with the JDK?

Its part of the JVM and its called HotSwap.

http://download.oracle.com/javase/1.4.2/docs/guide/jpda/enhancements.html

This feature is usually called "hot code replace" and was introduced in Java 1.4 - it's part of the Java Virtual Machine Debug Interface and various APIs on top of that.

So it's not specific to Eclipse, but I don't think any of the command line tools that come with the JDK support it.