title: To change date format from string
body: <p>I used datebox in gwt framework.The values of datebox are stored in database as a string in field t3.
  when I print jasper report, The value of t3 '11/02/2014' comes out as '11022014'. And that,I used this format,but there are some errors.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" name="RosterReport" pageWidth="700" pageHeight="595" orientation="Landscape" columnWidth="660" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20"&gt;
      &lt;property name="ireport.zoom" value="1.0"/&gt;
      &lt;property name="ireport.x" value="0"/&gt;
      &lt;property name="ireport.y" value="0"/&gt;
      &lt;field name="t1" class="java.lang.String"/&gt;
      &lt;field name="t2" class="java.lang.String"/&gt;
      &lt;field name="t3" class="java.lang.String"/&gt;
      &lt;field name="t4" class="java.lang.String"/&gt;
      &lt;field name="t5" class="java.lang.String"/&gt;
      &lt;variable name="date1" class="java.util.Date"&gt;
          &lt;variableExpression&gt;&lt;![CDATA[new SimpleDateFormat("MM/dd/yyyy").format($F{t3})]]&gt;&lt;/variableExpression&gt;
      &lt;/variable&gt;
      &lt;variable name="date2" class="java.lang.String"&gt;
          &lt;variableExpression&gt;&lt;![CDATA[new SimpleDateFormat("MM/dd/yyyy").format($F{t4})]]&gt;&lt;/variableExpression&gt;
      &lt;/variable&gt;
      &lt;background&gt;
          &lt;band splitType="Stretch"/&gt;
      &lt;/background&gt;
      &lt;title&gt;
          &lt;band height="58" splitType="Stretch"&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="247" y="17" width="153" height="39"/&gt;
                  &lt;textElement textAlignment="Center" verticalAlignment="Middle"&gt;
                      &lt;font size="12" isBold="true"/&gt;
                  &lt;/textElement&gt;
                  &lt;text&gt;&lt;![CDATA[Report for Roster]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="530" y="0" width="43" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;text&gt;&lt;![CDATA[Printed;]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
              &lt;textField&gt;
                  &lt;reportElement x="573" y="0" width="87" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;textFieldExpression&gt;&lt;![CDATA[new java.util.Date()]]&gt;&lt;/textFieldExpression&gt;
              &lt;/textField&gt;
          &lt;/band&gt;
      &lt;/title&gt;
      &lt;pageHeader&gt;
          &lt;band height="6" splitType="Stretch"/&gt;
      &lt;/pageHeader&gt;
      &lt;columnHeader&gt;
          &lt;band height="22" splitType="Stretch"&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="115" y="0" width="81" height="20"/&gt;
                  &lt;textElement&gt;
                      &lt;font isBold="true"/&gt;
                  &lt;/textElement&gt;
                  &lt;text&gt;&lt;![CDATA[Code]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="196" y="0" width="100" height="20"/&gt;
                  &lt;textElement&gt;
                      &lt;font isBold="true"/&gt;
                  &lt;/textElement&gt;
                  &lt;text&gt;&lt;![CDATA[Description]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="296" y="0" width="73" height="20"/&gt;
                  &lt;textElement&gt;
                      &lt;font isBold="true"/&gt;
                  &lt;/textElement&gt;
                  &lt;text&gt;&lt;![CDATA[Start Date]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="369" y="0" width="78" height="20"/&gt;
                  &lt;textElement&gt;
                      &lt;font isBold="true"/&gt;
                  &lt;/textElement&gt;
                  &lt;text&gt;&lt;![CDATA[End Date]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
              &lt;staticText&gt;
                  &lt;reportElement x="447" y="0" width="100" height="20"/&gt;
                  &lt;textElement&gt;
                      &lt;font isBold="true"/&gt;
                  &lt;/textElement&gt;
                  &lt;text&gt;&lt;![CDATA[Remark]]&gt;&lt;/text&gt;
              &lt;/staticText&gt;
          &lt;/band&gt;
      &lt;/columnHeader&gt;
      &lt;detail&gt;
          &lt;band height="34" splitType="Stretch"&gt;
              &lt;textField&gt;
                  &lt;reportElement x="196" y="0" width="100" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;textFieldExpression&gt;&lt;![CDATA[$F{t2}]]&gt;&lt;/textFieldExpression&gt;
              &lt;/textField&gt;
              &lt;textField&gt;
                  &lt;reportElement x="447" y="0" width="100" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;textFieldExpression&gt;&lt;![CDATA[$F{t5}]]&gt;&lt;/textFieldExpression&gt;
              &lt;/textField&gt;
              &lt;textField&gt;
                  &lt;reportElement x="115" y="0" width="81" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;textFieldExpression&gt;&lt;![CDATA[$F{t1}]]&gt;&lt;/textFieldExpression&gt;
              &lt;/textField&gt;
              &lt;textField&gt;
                  &lt;reportElement x="300" y="0" width="69" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;textFieldExpression&gt;&lt;![CDATA[$V{date1}]]&gt;&lt;/textFieldExpression&gt;
              &lt;/textField&gt;
              &lt;textField&gt;
                  &lt;reportElement x="369" y="0" width="78" height="20"/&gt;
                  &lt;textElement/&gt;
                  &lt;textFieldExpression&gt;&lt;![CDATA[$V{date2}]]&gt;&lt;/textFieldExpression&gt;
              &lt;/textField&gt;
          &lt;/band&gt;
      &lt;/detail&gt;
      &lt;columnFooter&gt;
          &lt;band height="14" splitType="Stretch"/&gt;
      &lt;/columnFooter&gt;
      &lt;pageFooter&gt;
          &lt;band height="9" splitType="Stretch"/&gt;
      &lt;/pageFooter&gt;
  &lt;/jasperReport&gt;
  </code></pre>
  
  <p>The error is </p>
  
  <pre><code>Source text : new SimpleDateFormat("MM/dd/yyyy").format($F{t3})
  Caused by: java.lang.IllegalArgumentException: Cannot format given Object as a Date
  </code></pre>
  
  <p>How to solve this error?</p>