 <p>I believe the <a href="http://wiki.eclipse.org/FAQ_What_is_hot_code_replace%3F" rel="nofollow">Hot Code Replace</a> in eclipse is what you meant in the problem:</p> <blockquote> <p>The idea is that you can start a debugging session on a given runtime workbench and change a Java file in your development workbench, and the debugger will replace the code in the receiving VM while it is running. No restart is required, hence the reference to "hot".</p> </blockquote> <p>But there are limitations:</p> <blockquote> <p>HCR only works when the class signature does not change; you cannot remove or add fields to existing classes, for instance. However, HCR can be used to change the body of a method.</p> </blockquote>