List jasperPrintList = new ArrayList();
jasperPrintList.add(JRLoader.loadObjectFromLocation("build/reports/Report1.jrprint"));
jasperPrintList.add(JRLoader.loadObjectFromLocation("build/reports/Report2.jrprint"));
jasperPrintList.add(JRLoader.loadObjectFromLocation("build/reports/Report3.jrprint"));
JRRtfExporter exporter = new JRRtfExporter();
exporter.setParameter(JRExporterParameter.JASPER_PRINT_LIST, jasperPrintList);
exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, "build/reports/BatchExportReport.rtf");
exporter.exportReport();
System.err.println("RTF creation time : " + (System.currentTimeMillis() - start));
}