How to break and display one ArrayList into multip

Question

I have a servlet which loads a properties file and contains a list of 100 test case names into an ArrayList object. After loading the servlet forwards to a JSP which displays the list in a table. The list is long so I would like some elegant way to display it in a table so that it breaks up into, for example, three or four columns on the JSP.

What I do now is break up the list into three sublists in the servlet:

//load properties
Properties props = new Properties();
        ArrayList<String> tests = new ArrayList<String>();
        props.load(getServletContext().getResourceAsStream("/WEB-INF/sailcertifier.properties"));
        Pattern pattern = Pattern.compile("[A-Z]{3}-[0-9]{2}");     
        for (Enumeration<Object> e = props.keys(); e.hasMoreElements();) {
            String key = (String) e.nextElement();
            Matcher m = pattern.matcher(key);
            if (m.find())
                tests.add(key);
        }
        Collections.sort(tests, new TestOrderComparator());
        confBean.setPossibleTests(tests.toArray(new String[tests.size()]));
        int third = tests.size() / 3;
        List<String> testSubset1 = tests.subList(0, third);
        List<String> testSubset2 = tests.subList(third, third * 2);
        List<String> testSubset3 = tests.subList(third * 2, tests.size());
        //store the bean as a request attribute
        request.setAttribute("testSet1", testSubset1.toArray(new String[testSubset1.size()]));
        request.setAttribute("testSet2", testSubset2.toArray(new String[testSubset2.size()]));
        request.setAttribute("testSet3", testSubset3.toArray(new String[testSubset3.size()]));
        request.setAttribute("testsConf", confBean);
        request.setAttribute("certProps", props);
        //forward to tests selection page
        String url = "/sailcertifier/jsp/testsSelection.jsp";
        RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(url);
        response.setContentType("application/javascript");
        try {
            dispatcher.forward(request, response);
        } catch (ServletException e) {
            e.printStackTrace();
        }

In the JSP I iterate through the sublists like so (adding some html elements for each case):

    <table>
        <tr>
            <td style="width: 33%">
                <table>
                    <tr>
                        <td>
                            <c:forEach var="testName" items="${testSet1}">
                                <tr>
                                    <td><label for="${testName}" id=${testName}Label>${testName}</label></td>
                                    <td><input id=${testName} type="checkbox" value=${testName} name="selTest"></input></td>
                                    <td><input id=${testName}Run type="button" value="Run Test" name="runButtons" /></td>
                                    <td><input id=${testName}ManPass type="button" value="Manual Pass" name="manPassButtons"/></td>
                                    <td><div id=${testName}Status style="width:100px"></td>
                                    <td></td>
                                    <td></td>
                                </tr>
                            </c:forEach>
                            <tr><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr>
                        </td>
                    </tr>
                </table>
            </td>
            <td style="width: 33%">
                <table>
                    <tr>
                        <td>
                            <c:forEach var="testName" items="${testSet2}">
                                <tr>
                                    <td><label for="${testName}" id=${testName}Label>${testName}</label></td>
                                    <td><input id=${testName} type="checkbox" value=${testName} name="selTest"></input></td>
                                    <td><input id=${testName}Run type="button" value="Run Test" name="runButtons" /></td>
                                    <td><input id=${testName}ManPass type="button" value="Manual Pass" name="manPassButtons"/></td>
                                    <td><div id=${testName}Status style="width:100px"></td>
                                    <td></td>
                                    <td></td>
                                </tr>
                            </c:forEach>
                            <tr><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr>
                        </td>
                    </tr>
                </table>
            </td>
            <td style="width: 33%">
                <table>
                    <tr>
                        <td>
                            <c:forEach var="testName" items="${testSet3}">
                                <tr>
                                    <td><label for="${testName}" id=${testName}Label>${testName}</label></td>
                                    <td><input id=${testName} type="checkbox" value=${testName} name="selTest"></input></td>
                                    <td><input id=${testName}Run type="button" value="Run Test" name="runButtons" /></td>
                                    <td><input id=${testName}ManPass type="button" value="Manual Pass" name="manPassButtons"/></td>
                                    <td><div id=${testName}Status style="width:100px"></td>
                                    <td></td>
                                </tr>
                            </c:forEach>
                        </td>
                    </tr>
                </table>
            </td>
        </tr>
    </table>

I admit using three JSTL for loops is kind of ugly (haven't figured out use the full original list yet). Is there a cleaner way to handle this, by using some jquery plugin (like jquery grid plugin) or other library (displaytag?) to handle the breaking up into rows evenly for me?

Answer 1

i'm not sure i've understood your request but suppose you have your 100 elements array and you want 3 columns to display them, so you can exploit "float" property to achieve that: just make a div of the width you want and iterate over the arrays making inner divs of width/3:

     <div style="width:600px;margin:auto;">
          <c:forEach var="testName" items="${testSet}">
              <div style="float:left;width:200px;">whatever you want to do with ${testName}</div>
          </c:forEach>
     </div>

Answer 2

Print a <tr>, then loop over the array list, then print each item in a <td> and print a </tr><tr> every n items, then end the loop over the array list and finally print a </tr> afterwards.

E.g. a new row every 3rd item:

<table>
    <tr>
        <c:forEach items="${items}" var="item" varStatus="loop">
            <c:if test="${not loop.first and loop.index % 3 == 0}">
                </tr><tr>
            </c:if>
            <td>${item}</td>
        </c:forEach>
    </tr>
</table>

The ${loop.index} returns the index of the current iteration round. The % 3 would only return 0 if it is dividable by 3 without a remainder (thus, when the index is 0, 3, 6, 9, 12, etc).