CoffeeDregs is a project developed by the Technical University of Eindhoven ( by Kees Huizing and Ruurd Kuiper. A netbeans grant is awarded for the development of a netbeans module.


The Concept

There is a need when learning how to program to visualize the execution processes "inside the computer". Students normally form a mental picture, by them selves, on how the code is executed in the computer. Some examples are: how an expression is evaluated, how a method call is executed and what the relations between classes or objects are. Experience shows that students tend to form a wrong picture of the process, hence a tool is needed to aid from the start in the visualization process.

CoffeeDregs aids first time students by visualizing the state of their code step by step. In contrast to debuggers CoffeeDregs visually renders the objects including fields and currently "active" methods calls. Students can advance line by line through their code, seeing instances of classes being created and changed, methods called, variables set etc. The tool is aimed at giving novice programmers relatively complete information about the execution at a level of abstraction that helps them to build a mental execution model. The model is generated from the code and hence is independent of specific style or methodology.

The visualization will be available as a module for Netbeans, via a push-button operation. It is visualized during execution in a separate pane in Netbeans.

The Goals

The main audience for this application are first time programmers that have yet to develop a mental concept of objects & communication between them.

  • Conceptually clean visualization of objects
  • As little deployment and configuration as possible for the end user
  • Stand alone & integrated with Netbeans

Screen shots

Screen shot of the application visualizing a simple java program

Contact & Information

There is a mailing list about the development of the application. You can subscribe here. Feedback and input is always appreciated!

There is also a WiKi about deployment & usage of the application here.

The Code & Downloads

You can grab a copy of the source here or get the compiled version and Netbeans Modules here url2. Requirements

  • Java SE JRE 6
  • Netbeans 6 or above (when deployed as module)


There are two ways of using the application each having a different path of deployment:

  • Stand alone
  • For the stand alone upzip the to a directory of your chosing and running the ExecView.jar file. Netbeans Module (6.0 or above)

To install the Netbeans Modules start up Netbeans, goto Tools>Plugins. Then goto the tabs Downloads and press the button Add Plugins.. and navigate to the plugins. After installation is complete a new icon will appear left of the Build main project button and in the Run menu.

Building the project

The project is creating using Netbeans so the easiest way of compiling it is just loading the project. Also Ant build are supported, try $ant run or $ant -do-jar-with-manifest

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