SpyJ is a Java utility designed to assist in development and debugging of Java graphical user interface (GUI) applications and applets.

It provides a graphical view of user interface components (such as frames, panels, buttons, etc.) and events at run time.

SpyJ allows a programmer:- See a hierarchical view of GUI components in a Java application or applet. - Select a component in the tree and examine properties. - Access public fields and execute methods using reflection- Use Finder tool to select a component under the mouse pointer. - See Java events (such as MouseEvent, ActionEvent, etc). - Debug AWT as well as Swing GUI applications - See method calls as well as field accesses and modifications.