getImageWritersByFormatName doesn't give proper values

[rini rachel]

Iterator writers = ImageIO.getImageWritersByFormatName(TIFF_FORMAT);

    if (!writers.hasNext()) {
        throw new RuntimeException(JAI_IMAGE_WRITER_MESSAGE);
    }

net.sourceforge.tess4j.TesseractException: java.lang.RuntimeException: Need to install JAI Image I/O package. Exception is thrown because of hasNext(). The same web application works in my mac machine, but not on an ubuntu machine. I am using tomcat server. Any help?