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JSwat is a graphical Java debugger front-end, written to use the Java Platform Debugger Architecture. JSwat is licensed under the Common Development and Distribution License 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.