A Java application is debugged in a Java micro device by selectively loading from a host computer into the device, a subset of Java classes and/or Java resource files that is used during the debugging the Java application in the device, that is automatically selected from a set of Java classes and/or Java resource files in the host computer. Thus, the need to load a potentially huge Java ARchive (JAR) file that contains all classes and/or resources, at the start of debugging, can be reduced or eliminated. The invention also may be used to load modules that are used during debugging an application on a device from a host computer.