Pentaho Reporting Flow Engine is a free Java report library.
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 It has the following features:
    * full on-screen print preview;
    * data obtained via Swing's TableModel interface
    (making it easy to print data directly from your application);
    * XML-based report definitions;
    * output to the screen, printer or various export formats
    (PDF, HTML, CSV, Excel, plain text);
    * support for servlets (uses the JFreeReport extensions)
    * extensive documentation in Acrobat PDF format, plus full Javadocs;