The paper presents an invariant-based generic tool to statically analyze Java programs in order to detect potential errors (bugs). We briefly discuss the supporting theoretical framework and highlight the results of the tool. It can automatically detect potential bugs such as illegal dereference and array bounds and report them before the program is executed. For a Java class, invariants related to the category of error under examination are automatically generated and used to assess the validity of variable usage in the implementation of this class. The tool provides a practical and extensible generic mechanism for error detection to help industry practitioners who work with an object oriented language such as Java. The presented mechanism is capable of addressing error detection for a variety of error categories that cannot be caught by flow-based static analysis tools.