JSwat is a graphical Java

Java (programming language)

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...

 debugger

Debugger

A debugger or debugging tool is a computer program that is used to test and debug other programs . The code to be examined might alternatively be running on an instruction set simulator , a technique that allows great power in its ability to halt when specific conditions are encountered but which...

 front-end, written to use the Java Platform Debugger Architecture

Java Platform Debugger Architecture

The Java Platform Debugger Architecture is a collection of APIs to debug Java code.* Java Debugger Interface - defines a high-level Java language interface which developers can easily use to write remote debugger application tools....

. JSwat is licensed under the Common Development and Distribution License

Common Development and Distribution License

Common Development and Distribution License is a free software license, produced by Sun Microsystems, based on the Mozilla Public License , version 1.1....

and is freely available in both binary and source code form. In addition to the graphical interface, there is a console based version which operates very much like jdb, the debugger included with the Java Development Kit.

Features include breakpoints with conditionals and monitors; colorized source code display; graphical display panels showing threads, stack frames, visible variables, and loaded classes; command interface for more advanced features; Java-like expression evaluation, including method invocation.